3D Navigation Tool among MESSENGER's Final Delivery Products to the Planetary Data System - May 18, 2017
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft was launched on August 3, 2004, and entered orbit about Mercury on March 18, 2011 (UTC). After orbiting the planet for more than four years, MESSENGER impacted Mercury on April 30, 2015. Sean C. Solomon, the Director of Columbia University's Lamont-Doherty Earth Observatory, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operated the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
First Global Topographic Model of Mercury among MESSENGER’s Latest Delivery to the Planetary Data System - May 6, 2016
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and inserted into orbit about Mercury on March 18, 2011 (UTC). After orbiting the planet for more than four years, the MESSENGER spacecraft impacted Mercury on April 30, 2015. Dr. Sean C. Solomon, the Director of Columbia University's Lamont-Doherty Earth Observatory, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operated the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
MESSENGER Data May Reveal the Remains of Mercury's Oldest Crust - March 7, 2016
Mercury's surface is unusually dark, an observation that until recently had planetary scientists mystified. But in a new study published today in Nature Geoscience, a team of researchers provides evidence that the darkening agent is carbon, a finding that offers important clues to the nature of the planet's original crust.
Patrick Peplowski, a research scientist at the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Maryland, and lead author of the paper, explains that earlier measurements of the chemistry of Mercury's surface only added to this mystery because they indicated that Mercury's surface has low abundances of iron and titanium, important constituents of the most common darkening agents on the Moon and other silicate bodies.
"A process of elimination led prior researchers to suggest that carbon may be the unidentified darkening agent, but we lacked proof," he said. "Spectral modeling of MESSENGER color imaging data suggested that weight-percent levels of carbon, likely in the form of graphite, would be required to darken Mercury's surface sufficiently. This level is unusually high, given that carbon is found at typical concentrations of only ~100 parts per million on the Moon, Earth and Mars."
Whatever the darkening agent, the scientists surmised that it was most concentrated in Mercury's low-reflectance material (LRM), which generally appears as deposits excavated from depth by impact cratering. The researchers examined MESSENGER Neutron Spectrometer measurements of LRM and surrounding materials, and they found that increases in low-energy neutrons are spatially correlated with LRM. Such increases require that the LRM have higher concentrations of an element that is inefficient at absorbing neutrons. Carbon is the only darkening agent suggested for Mercury that is also an inefficient neutron absorber.
These measurements were possible only late in MESSENGER's second extended mission, when the spacecraft regularly passed within tens of kilometers of Mercury's surface -- a necessary condition to resolve LRM deposits with the Neutron Spectrometer. Prior measurements acquired at altitudes greater than 200 kilometers couldn't resolve such deposits. The data used to identify carbon included measurements taken just days before MESSENGER impacted Mercury in April 2015.
"The global mapping of LRM shows that its source regions must typically lie deep within Mercury's crust, because the deposits are brought to the surface only by large impact craters," said coauthor Rachel Klima, a planetary geologist at APL who was instrumental in analyzing the multispectral image data to identify occurrences of LRM.
Like Earth's Moon and the other inner planets, Mercury likely had a global magma ocean when it was young and the surface was very hot, according to Klima. "Experiments and modeling show that as this magma ocean cooled and minerals began to crystallize, minerals that solidified would all sink with the exception of graphite, which would have been buoyant and would have accumulated as the original crust of Mercury. We think that LRM may contain remnants of this primordial crust. If so, we may be observing the remains of Mercury's original, 4.6-billion-year-old surface."
These findings not only directly test hypotheses for how Mercury's earliest crust formed but also provide clues about the volatile composition of the material from which Mercury accreted, "which in turn tells us about the distribution of material in orbit about the Sun during solar system formation," Klima said.
Planetary scientists said there are still many big questions to be answered. For one, what are the other minerals that make up Mercury's crust?
"We have some ideas from elemental data from MESSENGER's X-Ray Spectrometer and Gamma-Ray Spectrometer, but because the surface is so low in iron we cannot use visible and near-infrared spectra to probe the mineralogical composition of surface materials in the way we normally do for other rocky bodies," Klima said.
The nature of LRM remains an important area of study, Peplowski adds. "If we've really identified the remains of Mercury's original crust, then understanding its properties provides a means for understanding Mercury's earliest history."
Additional coauthors on this paper include APL's David Lawrence, Carolyn Ernst, Brett Denevi, John Goldstein and Scott Murchie; Elizabeth Frank and Larry Nittler, of the Carnegie Institution of Washington; and MESSENGER Principal Investigator Sean Solomon, of the Lamont-Doherty Earth Observatory, Columbia University.
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and inserted into orbit about Mercury on March 18, 2011 (UTC). After orbiting the planet for more than four years, MESSENGER impacted Mercury on April 30, 2015. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operated the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
MESSENGER's Brett Denevi Awarded Top Scientist Honor from Maryland Academy - November 24, 2015
The Maryland Academy of Sciences presented MESSENGER Team Member Brett Denevi with their Outstanding Young Scientist award during a ceremony on November 18 at the Maryland Science Center in Baltimore.
The Outstanding Young Scientist award program was established in 1959 to recognize and celebrate extraordinary contributions of young Maryland scientists.
Denevi, the Deputy Instrument Scientist for the Mercury Dual Imaging System (MDIS) on the MESSENGER spacecraft, is "an unusually accomplished young scientist who has helped to solve multiple difficult problems, the solutions to which have contributed to our basic understanding of how the solar system has evolved and the processes that drove its evolution," stated MESSENGER Co-Investigator Scott Murchie.
As a postdoctoral scientist at Arizona State University and later a planetary geologist at the Johns Hopkins University Applied Physics Laboratory (APL), Denevi was instrumental in helping to answer three of the six questions that framed the scientific objectives for the MESSENGER mission to Mercury. From multispectral images taken during MESSENGER's three flybys of Mercury, she led a paper demonstrating that much of Mercury's outer crust formed by volcanic processes. After joining APL in 2010, her maps of geological units derived from orbital images were used by the science team to address questions about Mercury's composition and the evolution of its interior.
While doing this research, she served in multiple capacities on the imaging team. She was the deputy in charge of planning observations and the lead for developing the final calibration of image data. "In other words, she applied her scientific knowledge to steering MESSENGER in the best scientific direction during its limited 4-year orbital lifetime," Murchie added.
Denevi is also a key participant in two other active planetary missions. She is a Co-Investigator on the Lunar Reconnaissance Orbiter Camera and a participating scientist on the Vesta phase of the Dawn mission. In her latter role, she is conducting pioneering research on optical effects of "space weathering" at ultraviolet wavelengths, a frontier area in the study of how planetary surfaces are modified by exposure to space.
Learn more about Denevi's work in this video.
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and inserted into orbit about Mercury on March 18, 2011 (UTC). After orbiting the planet for more than four years, MESSENGER impacted Mercury on April 30, 2015. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operated the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
Former MESSENGER Mission Manager Robert Farquhar Dies at Age 83 - October 23, 2015
Robert W. Farquhar, an early MESSENGER Mission Manager and a planetary trajectory pioneer who designed some of the most esoteric and complex spacecraft trajectories ever attempted, died on October 18, at the age of 83. A 50-year veteran of deep-space missions, Farquhar made pivotal contributions to the exploration of comets, asteroids, and the planets.
"Bob Farquhar was critical to the MESSENGER mission, from initial concept through launch and early operations," offered MESSENGER Principal Investigator Sean Solomon, of Columbia University's Lamont-Doherty Earth Observatory. "His competitive drive to achieve new firsts in space, his enthusiasm for attempting difficult tasks, and his brilliantly creative and technically thorough solutions to mission design challenges set a tone for the entire MESSENGER team. That MESSENGER was selected for flight, completed a record six planetary flybys, and became the first spacecraft to successfully orbit Mercury is in no small measure the result of Bob's inspiration, passion, and skill at problem solving. The entire MESSENGER team will miss him."
Farquhar was born in 1932 and raised in Chicago. He showed an interest in aviation as a child, reading about the topic and designing and building model airplanes. After serving in the Army in Japan during the Korean War, he studied aeronautical engineering at the University of Illinois and received his bachelor's degree with honors in 1959. He went on to earn a master's degree from the University of California, Los Angeles, in 1961. He worked briefly at Lockheed Missiles and Space Company in Sunnyvale, California, after which he completed a Ph.D. at Stanford University in 1969.
From 1969 to 1990, Farquhar worked at NASA's Goddard Space Flight Center in Greenbelt, Maryland, and at NASA Headquarters in Washington, D.C. In 1988, as Chief of Advanced Programs with the Space Physics Division, and Program Manager for the Discovery Program with the Solar System Exploration Division, he became involved in planning spacecraft missions to Mercury and Pluto.
"I was intrigued with the possibility of developing low or moderate-cost mission and spacecraft designs that could lead to realizable flight missions with many 'firsts,'" he wrote in his memoir, Fifty Years on the Space Frontier: Halo Orbits, Comets, Asteroids, and More.
Farquhar commissioned a study from the Jet Propulsion Laboratory (JPL) of a Mercury orbiter mission. JPL proposed a two-spacecraft Mercury Dual Orbiter (MDO) mission that would be launched on a single launch vehicle. Although the MDO mission was never selected for flight, several aspects of its mission design and operations concepts were adopted by the MESSENGER mission.
MESSENGER was selected by NASA as the seventh Discovery mission in 1999, and Farquhar -- by that time at the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Maryland -- was appointed Mission Manager during the mission's development phase. In that role, he supervised the mission design and navigation tasks, and he coordinated many activities of the science, engineering, and mission operations teams. He also worked closely with Deep Space Network (DSN) representatives at JPL to ensure that MESSENGER would have adequate DSN coverage following launch.
As Mission Manager, Farquhar was heavily involved in MESSENGER's pre-launch mission design, said his long-time collaborator David Dunham. "He made a notable decision late in the spacecraft design process when he found out that the spacecraft could not deliver a delta-V in all directions. Bob insisted on correcting that deficiency by adding two small thrusters, later informally called the 'Farquhar thrusters,' pointing toward the Sun through holes cut in the sunshade."
Farquhar retired from APL in 2007 and stepped down from his position as Mission Manager. In a new position he accepted at KinetX, Inc., he remained involved with the mission, serving as an advisor for MESSENGER's navigation team.
In his memoir, he wrote that his most important contribution to the MESSENGER mission was initiating the MDO study. It "changed the mind-set of NASA and the scientific community where a majority of people believed that a Mercury orbiter mission could only be done by employing solar-electric propulsion," he wrote. "This study set the stage for the acceptance of a low-cost ballistic mission to orbit Mercury."
In addition to MESSENGER, Farquhar made fundamental contributions to several other space missions, including the Comet Nucleus Tour (CONTOUR). He served as the first Mission Manager for NASA's New Horizons mission. Following a trajectory that Farquhar envisioned, that spacecraft flew past dwarf planet Pluto and its family of small moons this past July. He also conceived, and was the flight director for, the Near Earth Asteroid Rendezvous (NEAR) mission to asteroid 433 Eros -- the first launch of the Discovery program and the first planetary exploration mission led by APL.
"Bob was like no other in his ability to look for and find interesting, attainable, low-cost, and unique space missions involving both spacecraft that had already completed their primary missions and spacecraft that were yet to be designed," said APL's Jim McAdams, MESSENGER's Mission Design Lead, who worked alongside Farquhar for more than two decades. "Bob secured funds for mission design studies to ensure that multiple viable launch opportunities were designed and prepared for launch, a key contribution given that additional mandated spacecraft testing contributed to MESSENGER launching during its second backup launch opportunity. He also developed the skills and contacts needed to help make these missions happen, even when doing so required a miraculous competitive upset that most wouldn't believe was possible."
Farquhar is survived by his wife, Irina, stepdaughter, Anya, and a host of relatives.
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and inserted into orbit about Mercury on March 18, 2011 (UTC). After orbiting the planet for more than four years, MESSENGER impacted Mercury on April 30, 2015. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operated the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
Planetary Data System Releases 14th Delivery of MESSENGER Data - October 9, 2015
Data collected during MESSENGER's 43rd through 49th months in orbit around Mercury were released to the public today by NASA's Planetary Data System (PDS), the network of nodes that archives and distributes data from NASA's planetary missions. With this release, all data acquired by the MESSENGER mission are now available online - data collected through eight full Mercury solar days of orbit about the innermost planet in our solar system.
NASA requires that all of its planetary missions archive their data in the PDS to provide documented, peer-reviewed datasets to the research community. This 14th delivery of MESSENGER data extends the formatted raw and calibrated data available at the PDS for the spacecraft's science instruments and the radio science investigation to the period from September 18, 2014, to April 30, 2015, when the MESSENGER mission ended with the spacecraft's anticipated impact onto Mercury's surface.
Ancillary spacecraft, planet, instrument, camera-matrix, and events (SPICE) data from launch through the end of spacecraft operations are included in this release.
The ACT-REACT QuickMap interactive Web interface to MESSENGER data has been updated to incorporate the full coverage of the Mercury Dual Imaging System (MDIS) orbital data and the Mercury Atmospheric and Surface Composition Spectrometer (MASCS) Visible and Infrared Spectrograph (VIRS) measurements included in this delivery. QuickMap can be accessed via links on the MESSENGER websites at http://messenger.jhuapl.edu/ and http://www.nasa.gov/messenger. MDIS mosaics can be downloaded here.
The data for this release are available online at https://pds.nasa.gov/tools/subscription_service/SS-20151009.shtml, and all of the MESSENGER data archived at the PDS are available at http://pds.nasa.gov.
This is the final scheduled release of MESSENGER raw data products. The final release of MESSENGER calibrated and advanced products is scheduled for May 6, 2016.
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and inserted into orbit about Mercury on March 18, 2011 (UTC). After orbiting the planet for more than four years, MESSENGER impacted Mercury on April 30, 2015. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operated the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
MESSENGER Team Celebrates 11th Anniversary of Launch - August 3, 2015
Eleven years ago today -- at 2:15:56 am EDT -- NASA's MESSENGER spacecraft was launched aboard a Boeing Delta II rocket from Cape Canaveral Air Force Station in Florida, and after more than 6 1/2 years in transit it became the first spacecraft to orbit the innermost planet in our solar system.
The spacecraft is no more; on April 30 it impacted the surface of Mercury, as expected. But the team of scientists and engineers who built and operated the probe continues to analyze the many terabytes of data acquired.
"MESSENGER the spacecraft may be no more, but the information it provided about Mercury continues to expand what we know about the planet and the origin of our solar system," said James Green, Director of NASA's Planetary Science Division. "The spacecraft already far exceeded our expectations, and we look forward to more fabulous results that will come from the analysis of the archived data."
In a video released today, "Making Mercury Whole," MESSENGER team members recount some highlights of the mission, originally planned to orbit Mercury for only one year, but ultimately orbiting the planet for more than four years.
"This has been an extraordinary year for planetary science, with discoveries from the innermost planet to Pluto and the outer reaches of the solar system, from comets to asteroids, and from rocky planets to gas giants," adds MESSENGER Principal Investigator Sean Solomon, of the Lamont-Doherty Earth Observatory at Columbia University. "Our Science Team is continuing to validate, archive, and analyze data from the entire MESSENGER mission, and we can expect that Mercury will give up a few more of its secrets before we're done."
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and entered orbit about Mercury on March 18, 2011 (UTC). After orbiting the planet for more than four years, MESSENGER impacted Mercury on April 30, 2015. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operated the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
Mercury's magnetic field, generated by a dynamo process in its outer core, has been in place far longer than previously known, a paper by MESSENGER Participating Scientist Catherine Johnson reports.
About 4 billion years ago, Mercury's magnetic field could have been much stronger than today, as indicated by low-altitude observations made by NASA's MESSENGER spacecraft that revealed evidence of magnetization of ancient crustal rocks on Mercury.
The MESSENGER spacecraft crashed onto Mercury last week after running out of fuel, but the mission provided a trove of new information on the planet closest to the Sun.
"From MESSENGER and Mariner 10 observations we already knew that Mercury has had a global magnetic field today and 40 years ago," said Johnson, a senior scientist at the Planetary Science Institute and lead author of "Low-altitude Magnetic Field Measurements by MESSENGER Reveal Mercury's Ancient Crustal Field," published today in the journal Science. Johnson is also a Professor of Geophysics at the University of British Columbia, Vancouver.
With MESSENGER orbiting Mercury closer than 100 kilometers from the planet's surface, the spacecraft's Magnetometer instrument that measures magnetic field strength and direction was able to resolve signals too small to be detected earlier at higher altitudes. The observed decrease in signal strength measured with changes in altitude from 15 to 80 kilometers confirms that the signals are due to the presence of magnetized crustal rocks, Johnson said.
Mercury is the only inner solar system body other than Earth that currently possesses a global magnetic field generated by a dynamo in a fluid metallic outer core. In Mercury, as in Earth, the outer core is molten iron.
"Magnetized rocks record the history of the magnetic field of a planet, a key ingredient in understanding its evolution," Johnson said. "We already know that around 3.7 to 3.9 billions years ago Mercury was volcanically and tectonically active. We now know that it also had a magnetic field at around that time."
"If we didn't have the recent very low-altitude observations, we would never have been able to discover these signals," said Johnson. "Mercury has just been waiting to tell us its story."
Visit http://www.psi.edu/news/mercurymagnetism for some images relating to Johnson's research. See also http://news.ubc.ca/2015/05/07/messenger-reveals-mercurys-magnetic-field-secrets/.
Media Contact: Alan Fischer, Planetary Science Institute, 520-382-0411, 520-622-6300, fischer@psi.edu .
Science Contact: Catherine Johnson, Senior Scientist, 619-846-9566, cjohnson@psi.edu.
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and entered orbit about Mercury on March 17, 2011 (March 18, 2011 UTC), to begin a study of its target planet. After more than four years in orbit about Mercury, MESSENGER crashed into the planet on April 30, 2015. Dr. Sean C. Solomon, the Director of Columbia University's Lamont-Doherty Earth Observatory, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operated the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
Mission controllers at the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Md., confirmed today that NASA's MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft impacted the surface of Mercury, as predicted, at 3:26 p.m. EDT this afternoon (3:34 p.m. ground time).
Mission controllers were able to confirm the end of operations just a few minutes later at 3:40 p.m., when no signal was detected by the Deep Space Network (DSN) station in Goldstone, California, at the time the spacecraft would have emerged from behind the planet had MESSENGER not impacted the surface. This conclusion was independently confirmed by the DSN's Radio Science team, who were simultaneously looking for the signal from MESSENGER from their posts in California.
MESSENGER was launched on August 3, 2004, and it began orbiting Mercury on March 18, 2011. The spacecraft completed its primary science objectives by March 2012. Because MESSENGER's initial discoveries raised important new questions and the payload remained healthy, the mission was extended twice, allowing the spacecraft to make observations from extraordinarily low altitudes and capture images and information about the planet in unprecedented detail.
Last month -- during a final short extension of the mission referred to as XM2'-- the team embarked on a hover campaign that allowed the spacecraft at its closest approach to operate within a narrow band of altitudes, 5 to 35 kilometers above the planet's surface. On April 28, the team successfully executed the last of seven orbit-correction maneuvers (the last four of which were conducted entirely with helium pressurant after the remaining liquid hydrazine had been depleted), which kept MESSENGER aloft for the additional month, sufficiently long for the spacecraft's instruments to collect critical information that could shed light on Mercury's crustal magnetic anomalies and ice-filled polar craters, among other features.
With no way to increase its altitude, MESSENGER was finally unable to resist the perturbations to its orbit by the Sun's gravitational pull, and it slammed into Mercury's surface at around 8,750 miles per hour, creating a new crater up to 52 feet wide.
"Today we bid a fond farewell to one of the most resilient and accomplished spacecraft ever to have explored our neighboring planets," said Sean Solomon, MESSENGER's Principal Investigator and Director of Columbia University's Lamont-Doherty Earth Observatory. "Our craft set a record for planetary flybys, spent more than four years in orbit about the planet closest to the Sun, and survived both punishing heat and extreme doses of radiation. Among its other achievements, MESSENGER determined Mercury's surface composition, revealed its geological history, discovered that its internal magnetic field is offset from the planet's center, taught us about Mercury's unusual internal structure, followed the chemical inventory of its exosphere with season and time of day, discovered novel aspects of its extraordinarily active magnetosphere, and verified that its polar deposits are dominantly water ice. A resourceful and committed team of engineers, mission operators, scientists, and managers can be extremely proud that the MESSENGER mission has surpassed all expectations and delivered a stunningly long list of discoveries that have changed our views not only of one of Earth's sibling planets but of the entire inner solar system."
MESSENGER's Final Hours
MESSENGER's last orbit with real-time flight operations began at 11:15 a.m. EDT, with initiation of the final delivery of data and images from Mercury via the DSN 70-m antenna in Madrid, Spain. See the last image delivered here.
After a planned transition to the 34-m DSS-15 antenna at Goldstone, California, at 2:40 p.m. EDT, mission operators later confirmed the switch to a beacon-only communication signal at 3:04 p.m. The mood in the Mission Operations Center at APL was both celebratory and somber, as team members watched MESSENGER's telemetry drop out for the last time after more than four years and 4,105 orbits at Mercury.
"We then monitored MESSENGER's beacon signal for about 25 additional minutes," said Mission Operations Manager Andy Calloway of APL. "It was strange to think that for those last three minutes MESSENGER had already impacted onto Mercury, but we could not confirm that fact yet because of the vast distance across space between Mercury and Earth. MESSENGER passed behind Mercury (as viewed from Earth) at 3:29 p.m., however the signal from our intrepid spacecraft started fading prior to that and dropped out for the last time at 3:25 p.m."
At 3:38 p.m. EDT, at the time the spacecraft would have emerged from behind the planet as viewed from the Goldstone station had MESSENGER not impacted, mission operators began monitoring for a signal, but as expected they were unable to establish communications between MESSENGER and the DSN. This radio silence was the confirmation of the end of the MESSENGER mission.
Before impact, MESSENGER's mission design team predicted that the spacecraft would pass several miles over the lava-filled Shakespeare impact basin before striking an unnamed ridge near 54.5 degrees North latitude and 210.1 degrees East longitude. Because the probe hit on the far side of the planet, no Earth-based telescope was able to observe the impact. Moreover, space-based telescopes are precluded from observing Mercury because of the planet's proximity to the Sun, exposure to which would damage sensitive optics and instruments.
A future Mercury mission, such as the BepiColombo mission now in development by the European Space Agency and Japan Aerospace Exploration Agency, might be able to identify the impact crater left behind by MESSENGER. The MESSENGER team has acquired images of the entire planet, so a future mission will have MESSENGER's observations of the region before the impact to use as a baseline for comparison with subsequent imaging data sets to help pinpoint MESSENGER's impact site. The impact crater should be one of the youngest on Mercury and should have exposed fresh material from Mercury's subsurface that will have been exposed to the effects of space weathering for only a limited and precisely known time, so multispectral observations of MESSENGER's crater will provide an important constraint on rates of optical maturation of Mercury's surface material.
"Going out with a bang as it impacts the surface of Mercury, we are celebrating MESSENGER as more than a successful mission," said John Grunsfeld, associate administrator for NASA's Science Mission Directorate in Washington. "The MESSENGER mission will continue to provide scientists with a bonanza of new results as we begin the next phase of this mission--analyzing the exciting data already in the archives, and unraveling the mysteries of Mercury."
MESSENGER's Education and Public Outreach team included the public in the final chapter of the MESSENGER story by sponsoring a "Name that Crater," competition, providing an opportunity for the public to name five impact craters. Thousands of submissions were received, and the winners were announced on April 29.
Although the MESSENGER flight mission has now officially ended, the science data collected by MESSENGER are archived in NASA's Planetary Data System, where they are preserved and remain accessible for future use by the scientific community for years and even decades to come. The Science Team will continue to use these data to pose and answer questions about Mercury's formation and evolution and the planet's place in our Solar System through the end of the MESSENGER project in May 2016.
Additional information about MESSENGER's top science findings is available here; the mission's technological innovations are detailed here; and videos of team members discussing the mission are available online here.
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and entered orbit about Mercury on March 17, 2011 (March 18, 2011 UTC), to begin a study of its target planet. After more than four years in orbit about Mercury, MESSENGER crashed into the planet on April 30, 2015. Dr. Sean C. Solomon, the Director of Columbia University's Lamont-Doherty Earth Observatory, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
Mercury Crater-Naming Contest Winners Announced - April 29, 2015
The MESSENGER Education and Public Outreach (EPO) Team, coordinated through the Carnegie Institution for Science, announces the winning names from its competition to name five impact craters on Mercury. The contest submissions had to be submitted by January 15, 2015, and the International Astronomical Union (IAU) -- the governing body of planetary and satellite nomenclature since 1919 -- made the selections from a semi-final submission of 17 artists' names. The newly selected crater names are Carolan, Enheduanna, Karsh, Kulthum, and Rivera.
Under IAU rules, all new craters on Mercury must be named after an artist, composer, or writer who was famous for more than 50 years and has been dead for more than three years.
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft was launched on August 3, 2004, and entered orbit about Mercury on March 18, 2011, to begin a yearlong study of its target planet. MESSENGER's first extended mission began on March 18, 2012, and ended one year later. MESSENGER is now in a second extended mission, which is scheduled to operate through April 2015. Dr. Sean C. Solomon, the Director of Columbia University's Lamont-Doherty Earth Observatory, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
MESSENGER mission controllers at the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Md., conducted the last of six planned maneuvers on April 24 to raise the spacecraft's minimum altitude sufficiently to extend orbital operations and further delay the probe's inevitable impact onto Mercury's surface.
With the usable on-board fuel consumed, this maneuver expelled gaseous helium -- originally carried to pressurize the fuel, but re-purposed as a propellant. Without a means of boosting the spacecraft's altitude, the tug of the Sun's gravity will draw the craft in to impact the planet on April 30, at about 8,750 miles per hour (3.91 kilometers per second), creating a crater as wide as 52 feet (16 meters).
The previous maneuver, completed on April 14, raised MESSENGER's minimum altitude above Mercury from 6.5 kilometers (4.0 miles) to 13.3 kilometers (8.3 miles). But because of progressive changes in the orbit over time, the spacecraft's minimum altitude continued to decrease.
At the start of yesterday's maneuver, at 1:23 p.m. EDT, MESSENGER was in an orbit with a closest approach of 8.3 kilometers (5.1 miles) above the surface of Mercury. With a velocity change of 1.53 meters per second (3.43 miles per hour), the spacecraft's four largest monopropellant thrusters released gaseous helium to nudge the spacecraft to an orbit with a closest approach altitude of 18.2 kilometers (11.3miles).
Mission controllers at APL verified the start of the maneuver 9.4 minutes later, when the first signals indicating spacecraft thruster activity reached NASA's Deep Space Network (DSN) tracking station in Goldstone, California. This was the third MESSENGER maneuver designed to adjust the course of the spacecraft using just helium gas.
Since MESSENGER's launch in 2004, mission engineers have been working in lockstep with KinetX Aerospace to conduct such maneuvers. KinetX, based in Simi Valley, California, is the first commercial company to navigate any spacecraft to distant planetary bodies. The team processes radiometric tracking measurements from NASA's DSN antennas to perform orbit determination for MESSENGER.
The KinetX team was key to successfully navigating the spacecraft to arrive at the planet, and then for maintaining precise knowledge of the spacecraft's position while in orbit, including these last two months during MESSENGER's "hover campaign."
"Navigating a spacecraft so close to a planet's surface had never been attempted before, but it was a risk worth taking given mission success had already been met, and the novel science observation opportunities available only at such very low altitudes," said Bobby Williams, who leads the KinetX Space Navigation and Flight Dynamics group. "The MESSENGER mission presented new technical challenges for mission design and navigation that were successfully met through close cooperation and innovation of the APL and KinetX flight operations teams."
MESSENGER Principal Investigator Sean Solomon, Director of Columbia University's Lamont-Doherty Earth Observatory, commented on yesterday's maneuver on behalf of the project's Science Team as the end of the mission draws near.
"Operating a spacecraft in orbit about Mercury, where the probe is exposed to punishing heat from the Sun and the planet's dayside surface as well as the harsh radiation environment of the inner heliosphere, would be challenge enough," he said. "But MESSENGER's mission design, navigation, engineering, and spacecraft operations teams have done much more. They've fought off the relentless action of solar gravity, made the most of every usable gram of propellant, and devised novel ways to modify the spacecraft trajectory never before accomplished in deep space. They've extended the duration of MESSENGER's orbital observations by more than a factor of four over the original plan, and an amazing set of scientific discoveries has been enabled by their creative efforts. This latest maneuver is icing on a multi-tiered cake of spectacular accomplishment. The MESSENGER mission will soon end, but its legacy of scientific knowledge and technical innovation will endure for as long as we study the planets and explore the Solar System."
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft was launched on August 3, 2004, and entered orbit about Mercury on March 18, 2011, to begin a yearlong study of its target planet. MESSENGER's first extended mission began on March 18, 2012, and ended one year later. MESSENGER is now in a second extended mission, which is scheduled to operate through April 2015. Dr. Sean C. Solomon, the Director of Columbia University's Lamont-Doherty Earth Observatory, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
NASA Celebrates MESSENGER Mission Prior to Surface Impact of Mercury - April 16, 2015
NASA's highly successful MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft is coming to the end of its operations. Mission engineers predict that the probe -- out of fuel and under gravity's spell -- will impact Mercury on April 30 at more than 8,750 miles per hour (3.91 kilometers per second).
The spacecraft launched on August 3, 2004, and travelled more than six and a half years before it was inserted into orbit about Mercury on March 18, 2011. The original plan was to orbit the planet for one Earth year, collecting data to answer six critical questions. But new questions raised by early findings motivated two extensions of orbital operations for a total of three more years. Moreover, through a series of technological innovations, MESSENGER's engineers devised a way to save fuel early on and leverage helium gas later, paving the way for a final one-month extension that enabled mission scientists to continue to acquired novel, low-altitude measurements of the planet closest to the Sun.
"MESSENGER had to survive heating from the Sun, heating from the dayside of Mercury, and the harsh radiation environment in the inner heliosphere, and the clearest demonstration that our innovative engineers were up to the task has been the spacecraft's longevity in one of the toughest neighborhoods in our Solar System," said MESSENGER Principal Investigator Sean Solomon, director of Columbia University's Lamont-Doherty Earth Observatory. "Moreover, all of the instruments that we selected nearly two decades ago have proven their worth and have yielded an amazing series of discoveries about the innermost planet."
"Although Mercury is one of Earth's nearest planetary neighbors, astonishingly little was known when we set out," Solomon continued. "MESSENGER has at last brought Mercury up to the level of understanding of its sister planets in the inner Solar System. Of course, the more we learn, the more new questions we can ask, and there are ample reasons to return to Mercury with new missions."
In a briefing at NASA Headquarters today, MESSENGER scientists and engineers ticked off the top science findings and technological innovations from the mission. Near the top of the list of science accomplishments is having provided compelling support for the hypothesis that Mercury harbors abundant water ice and other frozen volatile materials in its permanently shadowed polar craters.
"The water now stored in ice deposits in the permanently shadowed floors of impact craters at Mercury's poles most likely was delivered to the innermost planet by the impacts of comets and volatile-rich asteroids," says Solomon. "Those same impacts also likely delivered the material in the dark layer discovered by MESSENGER to cover most polar deposits and interpreted, on the basis of its sublimation temperature and low reflectance, to be carbonaceous. By this interpretation, Mercury's polar regions serve as a witness plate to the delivery to the inner solar system of water and organic compounds from the outer solar system, a process that much earlier may have led to prebiotic chemical synthesis and the origin of life on Earth. MESSENGER's findings have made Mercury an even more interesting body for future exploration than before our mission."
The technological innovations that grew out of the MESSENGER mission are equally impressive, said MESSENGER Project Manager Helene Winters and MESSENGER Mission Systems Engineer Daniel O'Shaughnessy, both of the Johns Hopkins University Applied Physics Laboratory in Laurel, Md.
Together, they presented the top 10 technology innovations, which included the development of MESSENGER's first line of thermal defense, a heat-resistant and highly reflective ceramic cloth sunshade that isolates the spacecraft's instruments and electronics from direct solar radiation.
"The front side of the sunshade routinely experiences temperatures in excess of 300 degrees Celsius (570 degrees Fahrenheit), whereas the majority of components in its shadow routinely operate near room temperature (20 degrees Celsius or 68 degrees Fahrenheit)," Winters explained. "The sunshade is extremely effective at isolating most of the vehicle from the Sun's radiation, but reflected infrared radiation from Mercury greatly influences the temperatures of MESSENGER's components behind the sunshade. The influence of Mercury is effectively managed with careful selection of vehicle orientation, to balance heating across the spacecraft, as well as an intricate system of heat pipes and radiators."
On April 14, mission operators at APL completed the fifth in a series of orbit correction maneuvers designed to delay MESSENGER's impact into Mercury. The last such maneuver is scheduled for April 24.
"Following this last maneuver, we will finally declare MESSENGER out of propellant, as this maneuver will deplete nearly all of our remaining helium gas," O'Shaughnessy said. "At that point, the spacecraft will no longer be capable of fighting the downward push of the Sun's gravity. After studying the planet intently for more than four years, MESSENGER's final act will be to leave an indelible mark on Mercury, as the spacecraft heads down to an inevitable surface impact."
Supporting materials for the press conference are available online.
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft was launched on August 3, 2004, and entered orbit about Mercury on March 18, 2011, to begin a yearlong study of its target planet. MESSENGER's first extended mission began on March 18, 2012, and ended one year later. MESSENGER is now in a second extended mission, which is scheduled to conclude no later than April 30, 2015. Dr. Sean C. Solomon, the Director of Columbia University's Lamont-Doherty Earth Observatory, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
The MESSENGER team is pulling out all the stops to give the spacecraft life far beyond its original design. On April 8, mission operators at the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Md., successfully conducted a contingency orbit-correction maneuver (OCM-15a), to supplement the April 6 burn (OCM-15) that concluded early when the last drops of hydrazine fuel were expended.
Had there been a little more hydrazine, OCM-15 would have raised MESSENGER's periapsis altitude a full 25 kilometers.
"The team couldn't be sure precisely how much liquid hydrazine remained onboard, and how much of that was accessible," explained APL's Karl Whittenburg, MESSENGER's Deputy Mission Operations Manager. "Onboard fault-protection software was designed to transition autonomously to use of gaseous helium for propulsion, should hydrazine depletion occur during this maneuver. Although the transition occurred as designed, our post-maneuver analyses indicated a shortfall in the desired trajectory change."
"To our knowledge, this is the first-ever use of a pressurant for a planned propulsion of a spacecraft, so we could only theorize how it might perform," Whittenburg continued. "OCM-15 gave us performance data on this technique, and we are now fully confident that future use of gaseous helium will continue to provide MESSENGER with a unique vantage point for studying Mercury."
Wednesday's contingency maneuver -- this time designed to use gaseous helium exclusively -- raised the spacecraft's minimum altitude above Mercury from 18.2 kilometers (11.3 miles) to 29.1 kilometers (18.1 miles). During the operation, a velocity change of 1.94 meters per second (4.34 miles per hour) was imparted, releasing the pressurant through the four largest monopropellant thrusters. Implemented when the spacecraft was at nearly the farthest point in its orbit from Mercury, today's maneuver increased the spacecraft's speed relative to Mercury and also increased the spacecraft's orbit period to 8 hours, 20.3 minutes.
This view of MESSENGER shows the spacecraft orientation at the start of OCM-15a. During the maneuver, the sunshade protected heat-sensitive components from direct sunlight. OCM-15a was planned and executed in a record two days' time and will keep MESSENGER on its aggressive course to make never-before-seen observations of the planet, made possible only during this final "hover campaign." The next maneuver, on April 14, will once again use gaseous helium to give MESSENGER and its science payload a bit more time to reveal more of the mysteries of the innermost planet in our solar system.
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft was launched on August 3, 2004, and entered orbit about Mercury on March 18, 2011, to begin a yearlong study of its target planet. MESSENGER's first extended mission began on March 18, 2012, and ended one year later. MESSENGER is now in a second extended mission, which is scheduled to conclude no later than April 30, 2015. Dr. Sean C. Solomon, the Director of Columbia University's Lamont-Doherty Earth Observatory, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
Latest Maneuver Illustrates Critical Role Telecommunications System Plays in Delaying MESSENGER's Mercury Impact - April 7, 2015
MESSENGER's orbit-correction maneuver on April 6 was a nail biter. It was the 15th such maneuver since the spacecraft entered orbit about Mercury in 2011, and the third in a series of increasingly risky "burns" designed to delay MESSENGER's inevitable impact onto Mercury's surface. Each maneuver illustrates the critical role that the spacecraft's radio frequency (RF) telecommunications system plays in its operation.
The RF telecommunications system is used to receive operational commands at the spacecraft from Earth, and to transmit data acquired in making science observations, and data indicative of spacecraft health, from the spacecraft to Earth. The RF subsystem also supports MESSENGER navigation by providing precise observations of the spacecraft's Doppler velocity and range in the line of sight to Earth.
The system consists of redundant General Dynamics Small Deep Space Transponders, solid-state power amplifiers, phased-array antennas, and medium- and low-gain antennas. The phased-array antennas, the first electronically steered antennas ever to be used in deep space, have no moving parts, thus reducing the likelihood of failure in the extreme thermal environment of Mercury. These antennas are designed to work at the 350 degrees Celsius ambient temperature.
Onboard Insight
"The RF system provides our only insight into what's going on aboard the spacecraft," explained MESSENGER Communications Engineer Dipak Srinivasan, of the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Md. Such situational awareness is particularly important as the team attempts -- in a series of increasingly risky maneuvers -- to raise the spacecraft's minimum altitude sufficiently to extend orbital operations as long as possible.
"We use data from the RF system to confirm whether a maneuver has started and completed properly," he said. "We can also look at the change in the signal's frequency -- caused by the spacecraft's changing motion and the resulting Doppler effect -- to provide instantaneous assessments on the maneuver status."
The frequent, almost back-to-back orbit-correction maneuvers (OCMs) of MESSENGER's "hover campaign" present a challenge to the RF system. "During OCMs, the spacecraft has to be oriented in a way that best supports the propulsion system and keeps the sunshade between the Sun and the spacecraft's thermally sensitive payload," Srinivasan added. "This requirement means that communications can suffer when we are forced to use our low-gain antennas to support communications with Earth. In such situations, the signal strength we receive on the ground is quite low, so we must optimize our ground configuration to maintain communications throughout the burn."
The Latest Maneuver
MESSENGER was nearly at its farthest point from Mercury in its eccentric orbit about the planet when Monday's maneuver was executed. The burn raised the spacecraft's minimum altitude above Mercury from 13.1 kilometers (8.1 miles) to 25.7 kilometers (16.0 miles). It increased the spacecraft's speed relative to Mercury and also added about 0.55 minutes to the spacecraft's eight-hour, 18.9-minute orbit period. Four of the 12 smallest monopropellant thrusters imparted a change in velocity of 1.77 meters per second (3.97 miles per hour).
The operation used all of MESSENGER's remaining usable hydrazine propellant from the small auxiliary fuel tank. It was completed over its final six minutes with helium pressurant being expelled through the same thrusters that were used with the first part of the maneuver.
Although no problems were reported during the maneuver, the usable propellant was depleted sooner than predicted. The MESSENGER flight operations team is planning a "clean-up" maneuver for April 8 (with a backup scheduled for April 11) that will again use helium pressurant to put the spacecraft back on schedule for OCM-16 on April 14.
Solar Conjunction Adds to the Thrill
The spacecraft is about to enter a superior solar conjunction, during which Mercury and MESSENGER will be on the far side of the Sun from Earth. "As we approach superior solar conjunction, the RF signal has to travel through more of the solar plasma," Srinivasan explained. "The plasma causes scintillations in the signal, disrupting it in both phase and amplitude. This phenomenon introduces noise in our received signal, deteriorating our signal-to-noise ratio and making it harder to decode the information from the spacecraft. As the angle between the spacecraft and Sun gets smaller and smaller, the signal eventually drops out completely, and we won't pick it up again until the spacecraft emerges from behind the Sun on the other side."
Having an OCM just before a superior solar conjunction is cutting it close, he admits. "Conjunctions always cause a slight worry, as the Sun prevents us from contacting the spacecraft for relatively long periods of time. But we have several conjunctions and maneuvers under our belt and we are confident the spacecraft will pull through okay," he said. "Fortunately, we have a proven fault-protection system on board, as well as seasoned mission operations and engineering teams ready to solve problems that may arise."
"Our engineering team continues to pull rabbits out of this mission's hat," said MESSENGER Deputy Principal Investigator Larry Nittler, of the Carnegie Institution of Washington. "Their efforts to keep our little spacecraft going long past all original expectations are truly heroic. They are working to keep the craft flying at low altitudes for a few extra weeks -- fighting against the gravitational pull of the Sun -- with empty fuel tanks, by blowing helium into space. The observations we make these last few weeks will add importantly to the long list of scientific discoveries from this amazing mission."
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft was launched on August 3, 2004, and entered orbit about Mercury on March 18, 2011, to begin a yearlong study of its target planet. MESSENGER's first extended mission began on March 18, 2012, and ended one year later. MESSENGER is now in a second extended mission, which is scheduled to conclude in March 2015. Dr. Sean C. Solomon, the Director of Columbia University's Lamont-Doherty Earth Observatory, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
Planned Maneuver Further Extends MESSENGER Orbital Operations - April 3, 2015
MESSENGER mission controllers at the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Md., conducted a maneuver yesterday to raise the spacecraft's minimum altitude sufficiently to extend orbital operations and further delay the probe's inevitable impact onto Mercury's surface.
The previous maneuver, completed on March 18, raised MESSENGER to an altitude at closest approach from 11.6 kilometers (7.2 miles) to 34.4 kilometers (21.4 miles) above the planet's surface. Because of progressive changes to the orbit over time in response to the gravitational pull of the Sun, the spacecraft's minimum altitude continued to decrease.
At the time of yesterday's maneuver, MESSENGER was in an orbit with a closest approach of 5.5 kilometers (3.4 miles) above the surface of Mercury. With a velocity change of 2.96 meters per second (6.63 miles per hour), four of the spacecraft's 12 smallest monopropellant thrusters nudged the spacecraft to an orbit with a closest approach altitude of 27.5 kilometers (17.1 miles). This maneuver also increased the spacecraft's speed relative to Mercury at the maximum distance from Mercury, adding about 1.2 minutes to the spacecraft's eight-hour, 17.6-minute orbit period.
The second orbit-correction maneuver (OCM) in MESSENGER's low-altitude hover campaign, also called the extension of the second extended mission, OCM-14 is the first propulsive course correction since December 2006 to use the two small thrusters that point sunward from the sunshade center panel. This view shows MESSENGER's orientation at the start of the maneuver.
MESSENGER was 200.6 million kilometers (124.6 million miles) from Earth when the 6.7-minute maneuver began at about 4:30 p.m. EDT. Mission controllers at APL verified the start of the maneuver 11.2 minutes later, after the first signals indicating spacecraft thruster activity reached NASA's Deep Space Network tracking station in Goldstone, Calif. The next maneuver, on April 6, will again raise the spacecraft's minimum altitude, allowing scientists to continue to collect images and data from MESSENGER's instruments. The 3.8 days between OCM-14 and OCM-15 will be the shortest time between any two MESSENGER maneuvers.
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft was launched on August 3, 2004, and entered orbit about Mercury on March 18, 2011, to begin a yearlong study of its target planet. MESSENGER's first extended mission began on March 18, 2012, and ended one year later. MESSENGER is now in a second extended mission, which is scheduled to conclude in March 2015. Dr. Sean C. Solomon, the Director of Columbia University's Lamont-Doherty Earth Observatory, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
MESSENGER Completes 4,000th Orbit of Mercury - March 27, 2015
On March 25, the MESSENGER spacecraft completed its 4,000th orbit of Mercury, and the lowest point in its orbit continues to move closer to the planet than ever before. The orbital phase of the MESSENGER mission, which was originally designed to collect data for one Earth year, just completed its fourth year of operation around Mercury. The mission has received a final extension to allow scientists to gather specific low-altitude data over an additional several weeks.
"When we completed our first Mercury flyby on January 14, 2008, after months of preparations and testing, we were amazed and perhaps even a little skeptical when the science team told us that the orbital phase could be characterized as two flybys of data collection every Earth day (and eventually three per day starting in April 2012)," said MESSENGER Mission Operations Manager Andy Calloway, of the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Md. "Now that we have surpassed 4,000 orbits and more than 17 Mercury years since Mercury orbit insertion, we know just what was meant by that prediction."
"Thanks to requisite optimization tools and techniques -- such as the SciBox science planning tool, customized downlink rate stepping during Deep Space Network contacts, and automated prioritization of data playback with the use of the Consultative Committee for Space Data Systems (CCSDS) file delivery protocol, to name just a few -- we have captured more than 275,000 images and downlinked more than four Earth years of data from our comprehensive suite of instruments," he continued. "MESSENGER really is the little spacecraft that could."
Last week, mission operators conducted the first of five final adjustments to MESSENGER's orbit to delay the inevitable impact onto the surface of Mercury. During these last several weeks (for which the project uses the term XM2' hover campaign), the spacecraft is maintaining an unprecedented range of periapsis altitudes between 6 and 38 kilometers (3.7 to 24 miles) above Mercury's surface, allowing scientists to continue to collect and return novel data until the final moments before impact.
"The MESSENGER milestone of 4,000 orbits around Mercury in just over four years is a testament to the talent and dedication of the teams that designed, built, and operated a spacecraft for which the original plan was to complete about 740 orbits during a single year after Mercury orbit insertion," said APL's James McAdams, MESSENGER's Mission Design Lead Engineer. "An exemplary science team and supportive NASA sponsorship and oversight have made the most of the mission extensions, leading to numerous new insights into the processes that formed and subsequently transformed our solar system's nearest planet to the Sun."
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft was launched on August 3, 2004, and entered orbit about Mercury on March 18, 2011, to begin a yearlong study of its target planet. MESSENGER's first extended mission began on March 18, 2012, and ended one year later. MESSENGER is now in a second extended mission, which is scheduled to conclude in March 2015. Dr. Sean C. Solomon, the Director of Columbia University's Lamont-Doherty Earth Observatory, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
MESSENGER will not go gentle into that good night. The mission will end sometime this spring, when the spacecraft runs out of propellant and the force of solar gravity causes it to impact the surface of Mercury. But the team initiated a "hover" observation campaign designed to gather scientific data from the planet at ultra-low altitudes until the last possible moment. Engineers have devised a series of orbit-correction maneuvers (OCMs) over the next five weeks -- the first of which was carried out today -- designed to delay the inevitable impact a bit longer.
A highly accurate OCM executed on January 21 targeting a 15-kilometer periapsis altitude -- the lowest to date -- set the stage for the hover campaign, in a short extension of the Second Extended Mission termed XM2-Prime (XM2'). The top science goals for XM2' will be carried out with the Magnetometer (MAG) and the Neutron Spectrometer (NS), and each instrument will target different objectives in different regions, explained MESSENGER Deputy Project Scientist Haje Korth, of The Johns Hopkins University Applied Physics Laboratory (APL), in Laurel, Md.
"With MAG, we will look for crustal magnetic anomalies," he said. "For instance, we have seen hints of crustal magnetization at higher altitudes (~70 kilometers) over the northern rise in Mercury's northern smooth plains. We will revisit this region at lower altitudes during XM2'. There may be other regions where such signals can be observed, and we will be looking for them."
"With NS, scientists will hone in on shadowed craters at northern high latitudes to search for water ice," Korth said. "We have found such evidence previously in the mission, but we hope to find more at low altitudes and spatially resolve the distribution within individual craters if we are lucky."
According to Korth, the observations enabled by this "saving throw" are no less significant than earlier ones. "Establishing the presence of crustal magnetic anomalies on Mercury would be a huge result, because it would extend the known temporal baseline for Mercury's internal magnetic field by eight orders of magnitude," he said. "Moreover, observing any such anomalies at different altitudes will allow the depth of the source to be determined."
"Since the periapsis altitude during the hover campaign is ~30 kilometers or less throughout XM2', we will have the opportunity to map half the planet with a magnetic magnifying glass, so to speak," he continued. "There are regions we have never seen at such low altitudes, and multiple areas of magnetic anomalies may be detected."
Staying Aloft
The ever-present tug of the Sun's gravity continues to perturb the spacecraft's orbit and drive closest approach downward toward the planet surface. For the last few weeks MESSENGER's altitude at closest approach has remained between 13 and 17 kilometers. To extend this hover campaign as long as possible, MESSENGER's mission design team optimized the trajectory design and the placement of each orbit-correction maneuver.
"We decided on a strategy that includes five maneuvers in as many weeks to keep the spacecraft within a tight altitude range of 5 to 39 kilometers above the surface of Mercury at closest approach," said APL's Jim McAdams, MESSENGER's Mission Design Lead Engineer.
Four of these five maneuvers occur in situations different from the dawn-dusk orbit orientation used for all earlier orbit-correction maneuvers in the mission, McAdams said. "During the interplanetary cruise phase, we designed similar course-correction maneuvers consisting of two or three separate, closely spaced maneuvers accomplished with different thruster sets. For XM2', we simplified the design and implementation of the final maneuvers, so that each will be executed at a single spacecraft orientation using one thruster set to maximize the orbit altitude change per unit mass of propellant consumed."
The maneuvers are not without risk, McAdams explained. "Increased uncertainty associated with effects on the spacecraft orbit of Mercury's gravity field at lower-than-ever altitudes, challenges in accurately predicting the spacecraft orbit when the Sun is near the spacecraft-to-Earth communications direction, and implementation of frequent OCMs make for a challenging final few weeks of flight operations," he said. "Depending on how each maneuver goes and on how Mercury's gravity field affects the minimum orbital altitude, we may need to plan and implement a contingency maneuver. Inserting a contingency maneuver will increase the likelihood of the hydrazine propellant running out earlier than planned."
So Far, So Good
This first maneuver went as planned. At the time of this most recent operation, MESSENGER was in an orbit with a closest approach of 11.6 kilometers (7.2 miles) above the surface of Mercury. With a velocity change of 3.07 meters per second (6.87 miles per hour), the spacecraft's four largest monopropellant thrusters (with a small contribution from four of the 12 smallest monopropellant thrusters) nudged the spacecraft to an orbit with a closest-approach altitude of 34.5 kilometers (21.4 miles).
This maneuver also increased the spacecraft's speed relative to Mercury at the maximum distance from Mercury, adding about 1.1 minutes to the spacecraft's eight-hour, 16.5-minute orbit period. OCM-13 used propellant from the small auxiliary fuel tank. This view shows MESSENGER's orientation at the start of the maneuver.
MESSENGER was 185.6 million kilometers (115.4 million miles) from Earth when the 32-second maneuver began at 11:00 a.m. EDT. Mission controllers at APL verified the start of the maneuver 10.3 minutes later, after the first signals indicating spacecraft thruster activity reached NASA's Deep Space Network tracking station in Goldstone, California.
The next maneuver, on April 2, will again raise the spacecraft's minimum altitude, allowing scientists to continue to collect images and data from MESSENGER's instruments.
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft was launched on August 3, 2004, and entered orbit about Mercury on March 18, 2011, to begin a yearlong study of its target planet. MESSENGER's first extended mission began on March 18, 2012, and ended one year later. MESSENGER is now in a second extended mission, which is scheduled to conclude in March 2015. Dr. Sean C. Solomon, the Director of Columbia University's Lamont-Doherty Earth Observatory, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
Today, the MESSENGER team celebrates the fourth anniversary of the spacecraft's Mercury orbit insertion. On the evening of March 17, 2011 (EDT), the spacecraft made history when it became the first to orbit the innermost planet. Over the last four years, its instruments have fully mapped Mercury's surface and yielded discoveries that have changed views on how the inner planets formed and evolved.
"MESSENGER truly is an extraordinary mission," said Peter Bedini, a senior management advisor and former project manager for the mission. "When it began its primary mission four years ago, the spacecraft had already traveled almost five billion miles and completed six planetary encounters. During its pre-orbital Mercury flybys alone, MESSENGER collected as much data as Mariner 10 -- the only other spacecraft ever to visit the innermost planet -- and began addressing questions about Mercury that had remained unanswered for more than 30 years."
"All objectives of the primary mission were easily met in the first year in orbit, and those findings stimulated questions that guided two successive extended missions," added Bedini, of the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Md. The latest findings are being discussed in 15 papers presented this week and were highlighted in a press conference yesterday at the 46th Lunar and Planetary Science Conference in The Woodlands, Texas. A video of that event is available online.
The mission has also contributed to NASA's technology base, said APL's David Grant, who served as the mission's project manager for five years, overseeing the development, integration, test, and launch of the spacecraft and subsequent mission operations, including the Earth flyby and two Venus flybys.
Grant offers two examples. MESSENGER is the first mission to utilize "solar sailing," that is, to correct the trajectory of the spacecraft with the Sun's radiation, saving propellant and extending mission operations. The project is also the first to use SciBox, an automated science planning and commanding tool, for all data acquisition. Given spacecraft operational constraints and instrument operational constraints and objectives, the tool provides the science planner with an optimized set of opportunities to take observations and produces an integrated command sequence for the payload.
"But there was one other first among equals: system engineering," Grant said. "I believe that the integration of the entire system presented the greatest challenge and led to our greatest success. Andy Santo, James Leary, Eric Finnegan, and Dan O'Shaughnessy served sequentially as MESSENGER's Mission Systems Engineers over a period spanning more than 15 years. Their performance was exceptional and really speaks for itself."
Now, after MESSENGER has logged more than 10 years in flight, the spacecraft and science instruments remain remarkably healthy, but the propulsion system is running on fumes. The force of solar gravity continues to perturb the spacecraft orbit in a manner that drives the probe downward toward the planet's surface with each closest approach, and the tanks of propellant -- needed to boost the spacecraft to higher altitudes -- are running dry. Tomorrow, the team will conduct the first of five final orbit-correction maneuvers designed to keep MESSENGER in orbit up to four weeks longer, possibly as late as April 30.
"The success of MESSENGER is a direct result of the talent and dedication of the team that designed and built it more than a decade ago, and of those who have operated it and directed the science data collection since launch in 2004," said APL's Helene Winters, MESSENGER's current project manager. "The results of this Discovery-class mission have rewritten the book on Mercury and filled an important gap in our understanding of our Solar System."
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft was launched on August 3, 2004, and entered orbit about Mercury on March 18, 2011, to begin a yearlong study of its target planet. MESSENGER's first extended mission began on March 18, 2012, and ended one year later. MESSENGER is now in a second extended mission, which is scheduled to conclude in March 2015. Dr. Sean C. Solomon, the Director of Columbia University's Lamont-Doherty Earth Observatory, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
The Woodlands, Texas -- NASA's MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) mission, now nearing the end of its fourth and final year of orbital operations at Mercury, is well into a low-altitude campaign that is returning images and measurements of the planet's surface and interior that are unprecedented in their resolution. MESSENGER scientists will discuss new findings from the low-altitude campaign and their implications for Mercury's geological evolution and the planet's geophysical and geochemical characteristics at a press briefing today at the 46th Lunar and Planetary Science Conference. Presentation materials and presenter biographies are available online.
Illuminating Hollows
Early in its primary orbital mission, MESSENGER discovered thousands of peculiar depressions at a variety of longitudes and latitudes, ranging in size from tens of meters to several kilometers across and tens of meters deep.
"These features, given the name 'hollows,' were a major surprise, because while we had been thinking of Mercury as a relic -- a planet that wasn't really changing anymore -- hollows appear to be younger than the planet's freshest impact craters. This finding suggests that Mercury is a planet whose surface is still evolving," says MESSENGER Participating Scientist David Blewett, a geologist at The Johns Hopkins University Applied Physics Laboratory (APL).
The team has since deduced that the hollows form through loss of a component in the rocks that is susceptible to sublimation (or a similar process) when exposed to the harsh environment of the planet's surface. "High-resolution images obtained by the spacecraft at low altitudes are revealing striking details about these hollows, including their young ages, their depths, and the diversity of locations in which they are found."
Mercury's Surface Composition
Since MESSENGER entered orbit about Mercury in March 2011, the spacecraft's X-Ray Spectrometer (XRS) has measured solar-induced X-ray fluorescence from the top ~100 micrometers of the planet's surface and determined the abundances of key rock-forming elements, including magnesium, aluminum, silicon, sulfur, calcium, titanium, and iron. MESSENGER observations at low altitudes have enabled the surface elemental composition of Mercury to be determined with unprecedented spatial resolution and reveal compositional heterogeneities at a scale of a few to a few tens of kilometers.
"At this scale, elemental data can be correlated to other properties, color and reflectance, for example, to improve our understanding of the detailed geological history of Mercury's crust," says Larry Nittler, MESSENGER Deputy Principal Investigator and a cosmochemist in the Department of Terrestrial Magnetism at the Carnegie Institution of Washington, Washington, D.C. "Moreover, recent measurements by both the XRS and MESSENGER's Neutron Spectrometer have also shown that the highest iron abundances on Mercury are associated with a large region containing the highest magnesium, calcium, and sulfur contents on the surface, possibly the remains of an ancient impact basin."
"As MESSENGER's periapsis altitude continues to decline before the end of the mission in April 2015, we anticipate XRS observations with even better spatial resolution," he adds. The results from the new XRS data will be integrated with complementary datasets to generate increasingly detailed maps of Mercury's geologically and geochemically heterogeneous surface.
Small Scarps Revealed
MESSENGER instruments have confirmed that the tectonic history of Mercury since the late heavy bombardment is dominated by contraction, and the most broadly distributed contractional tectonic landforms on Mercury are lobate scarps, the surface manifestation of thrust faults. These scarps are often hundreds of kilometers long and display hundreds to thousands of meters of relief. High-resolution images obtained during MESSENGER's low-altitude campaign have revealed a population of small fault scarps that can be more than an order of magnitude smaller in size than their larger counterparts and are comparable in scale to similar small scarps on the Moon.
"Small lunar scarps are likely less than 50 million years old on the basis of the rate of degradation of small landforms by continuous meteoroid bombardment, and because the cratering rate on Mercury is as much as a factor of ~3 greater than on the Moon, small scarps on Mercury may be substantially younger," says Thomas Watters, a MESSENGER Participating Scientist and senior scientist in the Center for Earth and Planetary Studies at the National Air and Space Museum, Smithsonian Institution. "Mercury's small scarps provide evidence that young faults are forming to accommodate the most recent phases of interior cooling and global contraction, raising the possibility that some of these small, young faults are active today."
Close up of Polar Deposits
Multiple datasets have provided evidence that water ice is present in permanently shadowed regions near Mercury's poles: Earth-based radar imaged radar-bright deposits, imaging and neutron spectrometry by MESSENGER instruments showed regions of permanent shadow and enhanced hydrogen in Mercury's north polar region, respectively, and thermal models indicated that temperatures could sustain surface and near-surface water ice in the permanently shadowed regions. Additionally, visible and near-infrared measurements have revealed that polar deposits display both high- and low-reflectance surfaces.
MESSENGER's low-altitude campaign has enabled imaging of the polar deposits in the permanently shadowed floors of Mercury's near-polar craters at higher resolutions than ever previously obtained, says Nancy Chabot, the Instrument Scientist for MESSENGER's Mercury Dual Imaging System (MDIS) and a planetary scientist with APL.
"Acquired with the broadband filter of MDIS, low-altitude images show that the deposits have sharp, well-defined boundaries and are not disrupted by small, young impact craters," says Chabot. "These characteristics indicate that the deposits are geologically young. This inference points either to delivery of volatiles to Mercury in the geologically recent past or to an ongoing process that restores the deposits and maintains the sharp boundaries."
"Despite several years of orbital observations of Mercury from higher altitudes, MESSENGER's low-altitude campaign has shown us many details of the planet's geological and geophysical processes for the first time," adds MESSENGER Principal Investigator Sean Solomon, Director of the Lamont-Doherty Earth Observatory at Columbia University. "Over the next six weeks, as observations are made at still lower altitudes, we expect that Mercury will give up a few more of its secrets before the books finally close on a mission that has exceeded all expectations."
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft was launched on August 3, 2004, and entered orbit about Mercury on March 18, 2011, to begin a yearlong study of its target planet. MESSENGER's first extended mission began on March 18, 2012, and ended one year later. MESSENGER is now in a second extended mission, which is scheduled to conclude in March 2015. Dr. Sean C. Solomon, the Director of Columbia University's Lamont-Doherty Earth Observatory, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
New MESSENGER Maps of Mercury's Surface Chemistry Provide Clues to the Planet's History - March 13, 2015
Two new papers from members of the MESSENGER Science Team provide global-scale maps of Mercury's surface chemistry that reveal previously unrecognized geochemical terranes -- large regions that have compositions distinct from their surroundings. The presence of these large terranes has important implications for the history of the planet.
The MESSENGER mission was designed to answer several key scientific questions, including the nature of Mercury's geological history. Remote sensing of the surface's chemical composition has a strong bearing on this and other questions. Since MESSENGER was inserted into orbit about Mercury in March 2011, data from the spacecraft's X-Ray Spectrometer (XRS) and Gamma-Ray Spectrometer (GRS) have provided information on the concentrations of potassium, thorium, uranium, sodium, chlorine, and silicon, as well as ratios relative to silicon of magnesium, aluminum, sulfur, calcium, and iron.
Until now, however, geochemical maps for some of these elements and ratios have been limited to one hemisphere and have had poor spatial resolution. In "Evidence for geochemical terranes on Mercury: Global mapping of major elements with MESSENGER's X-Ray Spectrometer," published this week in Earth and Planetary Science Letters, the authors used a novel methodology to produce global maps of the magnesium/silicon and aluminum/silicon abundance ratios across Mercury's surface from data acquired by MESSENGER's XRS.
These are the first global geochemical maps of Mercury, and the first maps of global extent for any planetary body acquired via the technique of X-ray fluorescence, by which X-rays emitted from the Sun's atmosphere allow the planet's surface composition to be examined. The global magnesium and aluminum maps were paired with less spatially complete maps of sulfur/silicon, calcium/silicon, and iron/silicon, as well as other MESSENGER datasets, to study the geochemical characteristics of Mercury's surface and to investigate the evolution of the planet's thin silicate shell.
The most obvious of Mercury's geochemical terranes is a large feature, spanning more than 5 million square kilometers. This terrane "exhibits the highest observed magnesium/silicon, sulfur/silicon, and calcium/silicon ratios, as well as some of the lowest aluminum/silicon ratios on the planet's surface," writes Shoshana Weider, a planetary geologist and Visiting Scientist at the Carnegie Institution of Washington. Weider and colleagues suggest that this "high-magnesium region" could be the site of an ancient impact basin. By this interpretation, the distinctive chemical signature of the region reflects a substantial contribution from mantle material that was exposed during a large impact event.
A second paper, "Geochemical terranes of Mercury's northern hemisphere as revealed by MESSENGER neutron measurements," now available online in Icarus, presents the first maps of the absorption of low-energy ("thermal") neutrons across Mercury's surface. The data used in this second study were obtained with the GRS anti-coincidence shield, which is sensitive to neutron emissions from the surface of Mercury.
"From these maps we may infer the distribution of thermal-neutron-absorbing elements across the planet, including iron, chlorine, and sodium," writes lead author Patrick Peplowski of The Johns Hopkins University Applied Physics Laboratory. "This information has been combined with other MESSENGER geochemical measurements, including the new XRS measurements, to identify and map four distinct geochemical terranes on Mercury."
According to Peplowski, the results indicate that the smooth plains interior to the Caloris basin, Mercury's largest well-preserved impact basin, have an elemental composition that is distinct from other volcanic plains units, suggesting that the parental magmas were partial melts from a chemically distinct portion of Mercury's mantle. Mercury's high-magnesium region, first recognized from the XRS measurements, also contains high concentrations of unidentified neutron-absorbing elements.
"Earlier MESSENGER data have shown that Mercury's surface was pervasively shaped by volcanic activity," notes Peplowski. "The magmas erupted long ago were derived from the partial melting of Mercury's mantle. The differences in composition that we are observing among geochemical terranes indicate that Mercury has a chemically heterogeneous mantle."
"The consistency of the new XRS and GRS maps provides a new dimension to our view of Mercury's surface," Weider adds. "The terranes we observe had not previously been identified on the basis of spectral reflectance or geological mapping."
"The crust we see on Mercury was largely formed more than three billion years ago," says Carnegie's Larry Nittler, Deputy Principal Investigator of the mission and co-author of both studies. "The remarkable chemical variability revealed by MESSENGER observations will provide critical constraints on future efforts to model and understand Mercury's bulk composition and the ancient geological processes that shaped the planet/s mantle and crust."
See related figure. Caption: Maps of magnesium/silicon (left) and thermal neutron absorption (right) across Mercury's surface (red indicates high values, blue low). These maps, together with maps of other elemental abundances, reveal the presence of distinct geochemical terranes. Volcanic smooth plains deposits are outlined in white.
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft was launched on August 3, 2004, and entered orbit about Mercury on March 18, 2011, to begin a yearlong study of its target planet. MESSENGER's first extended mission began on March 18, 2012, and ended one year later. MESSENGER is now in a second extended mission, which is scheduled to conclude in March 2015. Dr. Sean C. Solomon, the Director of Columbia University's Lamont-Doherty Earth Observatory, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
NASA's Planetary Data System (PDS) today released data collected from the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) mission during its 37th through 42nd months in orbit about Mercury.
NASA requires that all of its planetary missions archive their data in the PDS, which makes available documented, peer-reviewed data to the research community. This 13th delivery from the MESSENGER team includes formatted raw and calibrated data collected through 17 September 2014 by the spacecraft's seven science instruments and the Radio Science investigation. Spacecraft, planet, instrument, camera-matrix, and events (SPICE) metadata from launch through the period of this release are also available.
The delivery includes new advanced products created from data acquired through March 17, 2014, encompassing the first six full Mercury solar days of MESSENGER orbital operations. Now available are global high-incidence east- and west-illumination maps and high-resolution regional targeted mosaics acquired by the Mercury Dual Imaging System (MDIS),
"Images for the global high-incidence maps were acquired when the Sun was very low on the horizon, which accentuates our view of surface topography because even small geologic features catch the Sun and cast long shadows," explained Brett Denevi, a planetary geologist at the Johns Hopkins University Applied Physics Laboratory (APL), in Laurel, Md., and the Deputy Instrument Scientist for MDIS. "MDIS took images just after dawn and just before dusk, because asymmetrical features, such as thrust faults, are likely more visible in one illumination direction than the other. Moreover, crater walls and features that appear in shadow in one map will be illuminated in the other."
Creating the global maps, as with the high-incidence mosaics, requires a compromise, she explained. "In order to obtain coverage as close to global as possible, we have to sacrifice image resolution in many areas. These global maps are complemented by the regional targeted mosaics, which provide high-resolution images of selected sites of high scientific interest."
"The targets were chosen by the science team as areas for further investigation, and they have provided some of our most spectacular views of small-scale features such as hollows, fresh impact craters, and volcanic vents," she said. "In some cases these views are monochrome images acquired with the narrow-angle camera, and in others we opted for images acquired using the color filters of the slightly lower-resolution wide-angle camera."
This PDS also includes viewing normalizations, flux maps, and two-dimensional pitch-angle products from the Fast Imaging Plasma Spectrometer (FIPS) on the Energetic Particle and Plasma Spectrometer (EPPS) instrument.
"The new FIPS PDS data products simultaneously provide users with the most often used two-dimensional and three-dimensional data products, as well as the tools needed to create their own," explained Jim Raines, a space plasma physicist at the University of Michigan and FIPS Instrument Scientist. "The new angular flux maps provide the best visualization of the direction that plasma ions are traveling in Mercury's space environment, which is a key quantity for understanding the behavior of the system. The new energy-resolved pitch-angle distributions give this information relative to the local magnetic field, which can be useful for identifying ions that are expected to impact Mercury's surface and cause space weathering."
"The viewing normalizations product contains the time-dependent rotation matrices needed for users to form their own versions of these and other multi-dimensional products, with arbitrary time accumulations," he added.
The ACT-REACT QuickMap interactive Web interface to MESSENGER data has been updated to incorporate orbital data from this release from the MDIS instrument and the Mercury Atmospheric and Surface Composition Spectrometer (MASCS) instrument's Visible and Infrared Spectrograph (VIRS). QuickMap can be accessed via links on the MESSENGER websites at http://messenger.jhuapl.edu/ and http://www.nasa.gov/messenger. The MDIS mosaics can be downloaded from ../Explore/Images.html#global-mosaics.
The data for this release are available online at http://pds.nasa.gov/subscription_service/SS-20150306.html, and all of the MESSENGER data archived at the PDS are available at http://pds.nasa.gov. The team will deliver the next mission data set for release by PDS in October.
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft was launched on August 3, 2004, and entered orbit about Mercury on March 17, 2011 (March 18, 2011 UTC), to begin a yearlong study of its target planet. MESSENGER's first extended mission began on March 18, 2012, and ended one year later. MESSENGER is now in a second extended mission, which is scheduled to end this spring. Dr. Sean C. Solomon, the Director of Columbia University's Lamont-Doherty Earth Observatory, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
Maneuver Successfully Delays MESSENGER's Impact, Extends Orbital Operations - January 21, 2015
MESSENGER mission controllers at the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Md., successfully conducted a maneuver today designed to raise the spacecraft's minimum altitude sufficiently to extend orbital operations and delay the probe's inevitable impact onto Mercury's surface until early spring.
The immediately previous maneuver, completed on October 24, 2014, raised MESSENGER to an altitude at closest approach from 25.4 kilometers (15.8 miles) to 184.4 kilometers (114.6 miles) above the planet's surface. Because of progressive changes to the orbit over time, the spacecraft's minimum altitude continued to decrease.
At the time of this most recent maneuver, MESSENGER was in an orbit with a closest approach of 25.7 kilometers (16.0 miles) above the surface of Mercury. With a velocity change of 9.67 meters per second (21.62 miles per hour), the spacecraft's four largest monopropellant thrusters (with a small contribution from four of the 12 smallest monopropellant thrusters) nudged the spacecraft to an orbit with a closest approach altitude of 105.1 km (65.3 miles).
This maneuver also increased the spacecraft's speed relative to Mercury at the maximum distance from Mercury, adding about 3.7 minutes to the spacecraft's eight-hour, 12.9-minute orbit period. This maneuver was the first during the mission to intentionally use both fuel and gaseous helium pressurant to impart the desired velocity change. The propellant was drawn from a small auxiliary fuel tank, and the gaseous helium was drawn from the main fuel tanks.
"This maneuver has demonstrated the safety of this concept and will allow us to characterize system performance during the use of cold gas propellant," said MESSENGER Mission Systems Engineer Dan O'Shaughnessy, of APL. "Such characterization will be necessary to forecast accurately the timing of the spacecraft's surface impact and to plan low-altitude maneuvers for the remainder of the mission."
This view shows MESSENGER's orientation soon after the start of the maneuver. The spacecraft was 118.9 million kilometers (73.9 million miles) from Earth when the 1-minute, 49-second maneuver began at 1:27 p.m. EDT. Mission controllers at APL verified the start of the maneuver 6.6 minutes later, after the first signals indicating spacecraft thruster activity reached NASA's Deep Space Network tracking station in Goldstone, California.
The next maneuver, on March 18, will again raise the spacecraft's minimum altitude, allowing scientists to continue to collect images and data from MESSENGER's instruments.
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft was launched on August 3, 2004, and entered orbit about Mercury on March 17, 2011 (March 18, 2011 UTC), to begin a yearlong study of its target planet. MESSENGER's first extended mission began on March 18, 2012, and ended one year later. MESSENGER is now in a second extended mission, which is scheduled to conclude in March 2015. Dr. Sean C. Solomon, the Director of Columbia University's Lamont-Doherty Earth Observatory, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
Last Chance: Mercury Crater-Naming Contest Ends January 15 - January 13, 2015
The MESSENGER Education and Public Outreach (EPO) Team is reminding interested parties that the competition to name five impact craters on Mercury closes on January 15, 2015. The contest, open to everyone except members of the mission's EPO team, was launched on December 15, 2014.
NASA's MESSENGER spacecraft has been in orbit about Mercury since March 2011. The mission's EPO team is led by Julie Edmonds of the Carnegie Institution for Science.
According to the International Astronomical Union (IAU) -- the governing body of planetary and satellite nomenclature since 1919 -- new names for craters on Mercury must be that of an artist, composer, or writer who was famous for more than 50 years and has been dead for more than three years. See the current list of named Mercury craters.
The EPO team's contest allows the public to immortalize an important person in the arts and humanities from anywhere in the world. Fifteen finalist names for craters will be submitted to the IAU for selection of the five winners. Winning submissions will be announced by the IAU to coincide with the end of MESSENGER's orbital operations in late March or April 2015. IAU decisions will be final.
Edmonds advises participants to research the artist, composer, or writer under consideration before filling out the contest entry. "Once online, registrants will be asked to submit a short description of their chosen individual's contributions to their field, as well as an authoritative source for background information," she said.
The name cannot have any political, religious, or military significance. Nor can other features in the Solar System have the same name. For example, Ansel Adams is not eligible because there is a feature on the Moon with the name Adams (even though it was not named for Ansel). Participants can check their ideas against the list of named Solar System features and enter the name in the "Search by Feature Name" box in the upper right corner.
The MESSENGER spacecraft has far surpassed expectations both in the duration of the mission and in the quality and quantity of data. The mission will end this spring as the tiny craft succumbs to gravity and impacts on Mercury. The EPO team organized the competition to celebrate the mission's achievements.
The original goal of MESSENGER was to take 2,500 images of the planet, but is has returned more than 250,000 images. "We now have a detailed, high-resolution map of the entire planet," Edmonds noted. "As scientists study the incredible data returned by MESSENGER, it becomes important to give names to surface features that are of special scientific interest. Having names for landforms such as mountains, craters, and cliffs makes it easier for scientists and others to communicate."
Enter the contest online at http://namecraters.carnegiescience.edu/.
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft was launched on August 3, 2004, and entered orbit about Mercury on March 17, 2011 (March 18, 2011 UTC), to begin a yearlong study of its target planet. MESSENGER's first extended mission began on March 18, 2012, and ended one year later. MESSENGER is now in a second extended mission, which is scheduled to conclude in March 2015. Dr. Sean C. Solomon, the Director of Columbia University's Lamont-Doherty Earth Observatory, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
Innovative use of Pressurant Extends MESSENGER's Mission, Enables Collection of New Data - December 24, 2014
The MESSENGER spacecraft will soon run literally on fumes. After more than 10 years traveling in space, nearly four of those orbiting Mercury, the spacecraft has expended most of its propellant and was on course to impact the planet's surface at the end of March 2015. But engineers on the team have devised a way to use the pressurization gas in the spacecraft's propulsion system to propel MESSENGER for as long as another month, allowing scientists to collect even more data about the planet closest to the Sun.
"MESSENGER has used nearly all of the onboard liquid propellant. Typically, when this liquid propellant is completely exhausted, a spacecraft can no longer make adjustments to its trajectory. For MESSENGER, this would have meant that we would no longer have been able to delay the inevitable impact with Mercury's surface," explained MESSENGER Mission Systems Engineer Dan O'Shaughnessy, of the Johns Hopkins University Applied Physics Laboratory (APL), in Laurel, Md. "However, gaseous helium was used to pressurize MESSENGER's propellant tanks, and this gas can be exploited to continue to make small adjustments to the trajectory."
This gas is less efficient, he added, but as effective as the liquid propellant at modifying the spacecraft's trajectory.
"The team continues to find inventive ways to keep MESSENGER going, all while providing an unprecedented vantage point for studying Mercury," said APL's Stewart Bushman, lead propulsion engineer for the mission. "To my knowledge this is the first time that helium pressurant has been intentionally used as a cold-gas propellant through hydrazine thrusters. These engines are not optimized to use pressurized gas as a propellant source. They have flow restrictors and orifices for hydrazine that reduce the feed pressure, hampering performance compared with actual cold-gas engines, which are little more than valves with a nozzle."
"Propellant, though a consumable, is usually not the limiting life factor on a spacecraft, as generally something else goes wrong first," he continued. "As such, we had to become creative with what we had available. Helium, with its low atomic weight, is preferred as a pressurant because it's light, but rarely as a cold gas propellant, because its low mass doesn't get you much bang for your buck."
Adjusting MESSENGER's trajectory will allow scientists to spend extra time exploring Mercury from close range. This past summer, the team launched a low-altitude observation campaign to acquire the highest-resolution images ever obtained of Mercury, enabling scientists to search for volcanic flow fronts, small-scale tectonic features, layering in crater walls, locations of impact melt, and new aspects of hollows -- detailed views that are providing a new understanding of Mercury's geological evolution.
"During the additional period of operations, up to four weeks, MESSENGER will measure variations in Mercury's internal magnetic field at shorter horizontal scales than ever before, scales comparable to the anticipated periapsis altitude between 7 km and 15 km above the planetary surface," said APL's Haje Korth, the instrument scientist for the Magnetometer. "Combining these observations with those obtained earlier in the mission at slightly higher altitudes will allow the depths of the sources of these variations to be determined. In addition, observations by MESSENGER's Neutron Spectrometer at the lowest altitudes of the mission will allow water ice deposits to be spatially resolved within individual impact craters at high northern latitudes."
MESSENGER's periapsis altitude is now approximately 101 kilometers and decreasing. The next orbit-correction maneuver on January 21, 2015, will raise the altitude at closest approach from approximately 25 kilometers to just over 80 kilometers.
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft was launched on August 3, 2004, and entered orbit about Mercury on March 17, 2011 (March 18, 2011 UTC), to begin a yearlong study of its target planet. MESSENGER's first extended mission began on March 18, 2012, and ended one year later. MESSENGER is now in a second extended mission, which is scheduled to conclude in March 2015. Dr. Sean C. Solomon, the Director of Columbia University's Lamont-Doherty Earth Observatory, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
MESSENGER Team Launches "Name a Crater" Competition - December 16, 2014
The MESSENGER Education and Public Outreach Team is holding a competition to name five impact craters on Mercury. The contest, open to all Earth citizens except for members of the mission's EPO team, runs from December 15, 2014, to January 15, 2015.
The spacecraft -- scheduled to impact Mercury in the spring -- has surpassed its originally planned primary orbital mission by three years. The EPO team organized the competition to celebrate the mission's achievements, said MESSENGER EPO Project Manager Julie Edmonds, of the Carnegie Institution of Washington.
"This brave little craft, not much bigger than a Volkswagen Beetle, has traveled more than 8 billion miles since 2004 -- getting to the planet and then in orbit," Edmonds said. "We would like to draw international attention to the achievements of the mission and the guiding engineers and scientists on Earth who have made the MESSENGER mission so outstandingly successful."
The MESSENGER team set out to take 2,500 images of the planet, but the spacecraft has returned more than 250,000 images. "We now have a detailed, high-resolution map of the entire planet," Edmonds noted. "As scientists study the incredible data returned by MESSENGER, it becomes important to give names to surface features that are of special scientific interest. Having names for land forms such as mountains, craters, and cliffs makes it easier for scientists and others to communicate." For example, she said, it's easier to refer to a feature as "Mt. Everest," rather than "the 8,484-meter peak located at a latitude of 27 degrees, 59 minutes, 17 seconds N, and longitude of 86 degrees, 55 minutes, 31 seconds E."
According to the International Astronomical Union (IAU), the arbiter of planetary and satellite nomenclature since its inception in 1919, all new craters must be named after an artist, composer, or writer who was famous for more than 50 years and has been dead for more than three years. See the current list of named Mercury craters.
Edmonds said participants should first research the individual they are considering before filling out the contest entry. "Once online, registrants will be asked to submit a short description of the individual's contributions to the arts, music, or literature, as well as an authoritative source for background information," she said.
The name should not have any political, religious, or military significance. It is also essential that there be no other features in the Solar System with the same name, she said. For example, Ansel Adams is not eligible because there is a feature on the Moon with the name Adams (even though it was not named for Ansel). Participants can check their ideas against the list of named Solar System features and enter the name in the "Search by Feature Name" box in the upper-right corner.
All entries will be reviewed by MESSENGER Team representatives and other experts. A short list of 15 names (three names per crater) will be submitted to the IAU, who will make the final selection.
Winning submissions will be announced by the IAU to coincide with the end of MESSENGER's mission operations in late March or April 2015.
Enter the contest online at http://namecraters.carnegiescience.edu/.
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft was launched on August 3, 2004, and entered orbit about Mercury on March 17, 2011 (March 18, 2011 UTC), to begin a yearlong study of its target planet. MESSENGER's first extended mission began on March 18, 2012, and ended one year later. MESSENGER is now in a second extended mission, which is scheduled to conclude in March 2015. Dr. Sean C. Solomon, the Director of Columbia University's Lamont-Doherty Earth Observatory, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
Third of Four Planned Maneuvers Extends MESSENGER Orbital Operations - October 24, 2014
MESSENGER mission controllers at the Johns Hopkins University Applied Physics Laboratory in Laurel, Md., conducted the third of four maneuvers today to raise the spacecraft's minimum altitude sufficiently to extend orbital operations and delay the probe's inevitable impact onto Mercury's surface until early next spring.
The first of the four maneuvers, completed on June 17, raised MESSENGER's altitude at closest approach from 115 kilometers (71.4 miles) to 156.4 kilometers (97.2 miles) above the planet's surface. The second of the four maneuvers, completed on September 12, raised MESSENGER's altitude at closest approach from 25.2 kilometers (15.7 miles) to 93.7 kilometers (58.2 miles) above the planet's surface. Because of progressive changes to the orbit over time, the spacecraft's minimum altitude has continued to decrease since September.
At the time of this most recent maneuver, MESSENGER was in an orbit with an altitude at closest approach of 26 kilometers (16.1 miles) above the surface of Mercury. With a velocity change of 19.37 meters per second (43.33 miles per hour), the spacecraft's four largest monopropellant thrusters (with a small contribution from four of the 12 smallest monopropellant thrusters) nudged the spacecraft to an orbit with a closest approach altitude of 185.2 kilometers (115.1 miles). This maneuver also increased the spacecraft's speed relative to Mercury at the maximum distance from Mercury, adding about 7.4 minutes to the spacecraft's eight-hour, five-minute orbit period.
This view shows MESSENGER's orientation shortly after the start of the maneuver.
MESSENGER was 116.9 million kilometers (72.64 million miles) from Earth when the 2 minute, 29 second maneuver began at 2:58 p.m. EDT. Mission controllers at APL verified the start of the maneuver 6.5 minutes later, after the first signals indicating spacecraft thruster activity reached NASA's Deep Space Network tracking station outside of Goldstone, California.
One more maneuver, on January 21, 2015, will again raise the spacecraft's minimum altitude, allowing the MESSENGER science team to continue to collect images and other data from the spacecraft's instruments.
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft was launched on August 3, 2004, and entered orbit about Mercury on March 17, 2011 (March 18, 2011 UTC), to begin a yearlong study of its target planet. MESSENGER's first extended mission began on March 18, 2012, and ended one year later. MESSENGER is now in a second extended mission, which is scheduled to conclude in March 2015. Dr. Sean C. Solomon, the Director of Columbia University's Lamont-Doherty Earth Observatory, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
MESSENGER Provides First Optical Images of Ice Near Mercury's North Pole - October 15, 2014
NASA's MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft has provided the first optical images of ice and other frozen volatile materials within permanently shadowed craters near Mercury's north pole. The images not only reveal the morphology of the frozen volatiles, but they also provide insight into when the ices were trapped and how they've evolved, according to an article published today in the journal, Geology.
Two decades ago, Earth-based radar images of Mercury revealed the polar deposits, postulated to consist of water ice. That hypothesis was later confirmed by MESSENGER through a combination of neutron spectrometry, thermal modeling, and infrared reflectometry. "But along with confirming the earlier idea, there is a lot new to be learned by seeing the deposits," said lead author Nancy Chabot, the Instrument Scientist for MESSENGER's Mercury Dual Imaging System (MDIS) and a planetary scientist at the Johns Hopkins University Applied Physics Laboratory in Laurel, Maryland.
Beginning with MESSENGER's first extended mission in 2012, scientists launched an imaging campaign with the broadband clear filter of MDIS's wide-angle camera (WAC). Although the polar deposits are in permanent shadow, through many refinements in the imaging, the WAC was able to obtain images of the surfaces of the deposits by leveraging very low levels of light scattered from illuminated crater walls. "It worked in spectacular fashion," said Chabot.
The team zeroed in on Prokofiev, the largest crater in Mercury's north polar region found to host radar-bright material. "Those images show extensive regions with distinctive reflectance properties," Chabot said. "A location interpreted as hosting widespread surface water ice exhibits a cratered texture indicating that the ice was emplaced more recently than any of the underlying craters."
In other areas, water ice is present, she said, "but it is covered by a thin layer of dark material inferred to consist of frozen organic-rich compounds." In the images of those areas, the dark deposits display sharp boundaries. "This result was a little surprising, because sharp boundaries indicate that the volatile deposits at Mercury's poles are geologically young, relative to the time scale for lateral mixing by impacts," said Chabot.
"One of the big questions we've been grappling with is 'When did Mercury's water ice deposits show up?' Are they billions of years old, or were they emplaced only recently?" Chabot said. "Understanding the age of these deposits has implications for understanding the delivery of water to all the terrestrial planets, including Earth."
Overall, the images indicate that Mercury's polar deposits either were delivered to the planet recently or are regularly restored at the surface through an ongoing process.
The images also reveal a noteworthy distinction between the Moon and Mercury, one that may shed additional light on the age of the frozen deposits. "The polar regions of Mercury show extensive areas that host water ice, but the Moon's polar regions -- which also have areas of permanent shadows and are actually colder -- look different," Chabot said.
"One explanation for differences between the Moon and Mercury could be that the volatile polar deposits on Mercury were recently emplaced," according to the paper. "If Mercury's currently substantial polar volatile inventory is the product of the most recent portion of a longer process, then a considerable mass of volatiles may have been delivered to the inner Solar System throughout its history."
"That's a key question," Chabot said. "Because if you can understand why one body looks one way and another looks different, you gain insight into the process that's behind it, which in turn is tied to the age and distribution of water ice in the Solar System. This will be a very interesting line of inquiry going forward."
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft was launched on August 3, 2004, and entered orbit about Mercury on March 17, 2011 (March 18, 2011 UTC), to begin a yearlong study of its target planet. MESSENGER's first extended mission began on March 18, 2012, and ended one year later. MESSENGER is now in a second extended mission, which is scheduled to conclude in March 2015. Dr. Sean C. Solomon, the Director of Columbia University's Lamont-Doherty Earth Observatory, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
MESSENGER's View of This Week's Lunar Eclipse - October 10, 2014
As millions of people observed the total lunar eclipse on October 8, MESSENGER was also watching. From its orbit about Mercury, the probe's camera captured several images of the Moon as it passed behind Earth and into the planet's shadow. From those images, the team created this movie, released today.
The animation was constructed from 31 images taken two minutes apart, from 5:18 a.m. to 6:18 a.m., EDT. The images start just before the Moon entered the darkest part of the Earth's shadow (the umbra).
"From Mercury, the Earth and Moon normally appear as if they were two very bright stars," noted Hari Nair, a planetary scientist at the Johns Hopkins University Applied Physics Laboratory, in Laurel, Md. "During a lunar eclipse, the Moon seems to disappear during its passage through the Earth's shadow, as shown in the movie."
MESSENGER was 107 million kilometers (66 million miles) from the Earth at the time of the lunar eclipse. The Earth is about five pixels across, and the Moon is just over one pixel across in the field of view of the spacecraft's narrow-angle camera, with about 40 pixels distance between them. According to Nair, the images are zoomed by a factor of two, and the Moon's brightness has been increased by a factor of about 25 to show its disappearance more clearly.
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft was launched on August 3, 2004, and entered orbit about Mercury on March 17, 2011 (March 18, 2011 UTC), to begin a yearlong study of its target planet. MESSENGER's first extended mission began on March 18, 2012, and ended one year later. MESSENGER is now in a second extended mission, which is scheduled to conclude in March 2015. Dr. Sean C. Solomon, the Director of Columbia University's Lamont-Doherty Earth Observatory, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
MESSENGER Systems Engineer Receives Inaugural Heinlein Award - October 7, 2014
Daniel O'Shaughnessy has been named the first recipient of the Heinlein Award for his development of solar sailing, a navigational technique that exploits the pressure of sunlight to control a spacecraft.
The Robert A. and Virginia Heinlein Prize Trust (HPT), a nonprofit foundation that promotes the commercial uses of space, created the Heinlein Award to recognize space-tested technologies that can benefit commercial space activities.
O'Shaughnessy, an engineer in the Space Exploration Sector at the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Maryland, employed the award-winning technique while he was the Guidance and Control Lead Engineer for the MESSENGER mission. The team relied on six planetary gravity assists to enable Mercury orbit insertion, but solar radiation pressure (SRP) had been seen as a threat to the success of these maneuvers.
"Because of the changing distance from the Sun during MESSENGER's cruise phase, the solar radiation pressure varied from one to 11 times the value experienced at Earth," explained O'Shaughnessy, who now serves as MESSENGER's Mission Systems Engineer. This variation in magnitude, as well as the attitude-dependent direction of the resulting disturbing force and torque, presented a substantial challenge to the mission design, navigation, and guidance and control teams, he said.
"The three Mercury flybys were designed to take MESSENGER to within 200 kilometers of the planet, so precise targeting was absolutely critical," he said. "If we flew too low, the probe could crash into Mercury. Overshoot the planet, and MESSENGER would have had to use its reserve fuel to correct for the acceleration loss. Either way, missing the target for any one of these flybys could have jeopardized the success of the mission."
Ultimately, the team found a way to use SRP to their advantage by exploiting the light pressure on the solar panels to perform fine trajectory corrections en route to Mercury. By changing the angle of the solar panels relative to the Sun, the amount of solar radiation pressure was varied to adjust the spacecraft trajectory more delicately than possible with thrusters. Minor errors are greatly amplified by gravity-assist maneuvers, so using radiation pressure to make very small corrections saved propellant and helped to extend the life of the mission.
"This work exemplifies the teamwork that has made the MESSENGER mission a success," said Mike Ryschkewitsch, head of SES. "Modifying the trajectory by solar sailing instead of thruster burns required tight coupling of mission designers, navigators, guidance and control engineers, and the spacecraft operations team. Active participation from each of these team members was essential to achieving the paradigm shift."
Heinlein Prize Trustee Arthur M. Dula said, in a statement, "The Heinlein Award recognizes demonstration in space of important technical accomplishments that benefit commercial activities."
"Although most commercial endeavors are not planning interplanetary trajectories, the demonstration of this capability has applications closer to home," O'Shaughnessy noted. "Many Earth-orbiting missions require precise orbit control and could potentially use this technique to provide very accurate orbit maintenance without requiring expensive on-board propellants."
O'Shaughnessy will receive a diploma and monetary award at a recognition dinner at the National Air and Space Museum in Washington, D.C., on November 21.
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft was launched on August 3, 2004, and entered orbit about Mercury on March 17, 2011 (March 18, 2011 UTC), to begin a yearlong study of its target planet. MESSENGER's first extended mission began on March 18, 2012, and ended one year later. MESSENGER is now in a second extended mission, which is scheduled to conclude in March 2015. Dr. Sean C. Solomon, the Director of Columbia University's Lamont-Doherty Earth Observatory, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
MESSENGER Principal Investigator to Receive National Medal of Science - October 3, 2014
MESSENGER Principal Investigator Sean Solomon will receive the nation's top scientific honor, the National Medal of Science. Solomon, the director of Columbia University's Lamont-Doherty Earth Observatory, will be awarded the medal at a White House ceremony later this year.
"These scholars and innovators have expanded our understanding of the world, made invaluable contributions to their fields, and helped improve countless lives," President Obama said in a statement on Friday. "Our nation has been enriched by their achievements, and by all the scientists and technologists across America dedicated to discovery, inquiry, and invention."
As head of NASA's MESSENGER mission to Mercury, Solomon has led the most comprehensive investigation yet of the closest planet to the Sun. Some of his other projects are household names in space science: the Magellan mission to Venus, the Mars Global Surveyor mission and the GRAIL mission to the Moon, which launched in 2011 and has mapped the Moon's gravitational field in unprecedented detail.
After nearly seven years traveling through space, the MESSENGER probe entered orbit about Mercury in 2011 and has been continuously mapping the planet's interior, surface, and atmosphere. Recent discoveries include ice in Mercury's northern craters and an iron-rich core fractionally far larger than Earth's. The probe will continue gathering data about the planet before it crash lands on Mercury at the end of March next year.
A geophysicist who has spent much of his career studying Earth's neighboring planets as well as Earth itself, Solomon became director of Lamont-Doherty in 2012 after serving for nearly two decades as director of the Carnegie Institution's Department of Terrestrial Magnetism in Washington, D.C. After finishing his Ph.D. in geophysics at Massachusetts Institute of Technology in 1971, he stayed on to teach and conduct research there for two decades. In 1978, he published a paper in the journal Geophysical Research Letters that explained how relatively small bodies like the Moon and Mercury evolved without the multiple tectonic plates found on Earth. This "one-plate planet" idea still holds in understanding the tectonics of the solar system's rocky inner planets.
At MIT, Solomon ran one of the earliest ocean-bottom seismometer labs. He investigated Earth's mid-ocean ridges by leaving those instruments at the bottom of the Atlantic, Pacific, and Indian oceans to record earthquakes on the seafloor and measure Earth's structure below. As a result, he made important contributions to understanding how Earth's multiple plates generate new crust below the sea, where most plates intersect. He moved to Carnegie in 1992. Among other roles, he served as principal investigator for Carnegie's part of the NASA Astrobiology Institute, which seeks to understand the origin of life on earth, and its potential to exist elsewhere.
Solomon is a member of the National Academy of Sciences and the American Academy of Arts and Sciences and has received numerous other awards, among them the Geological Society of America's G. K. Gilbert Award and American Geophysical Union's Harry H. Hess Medal. When he stepped down as a director at Carnegie in 2011, colleagues arranged to have a previously discovered asteroid named after him. Asteroid 25137 Seansolomon, about a mile and half wide, is currently orbiting the Sun between Mars and Jupiter.
The National Medal of Science was created in 1959 and is administered for the White House by the National Science Foundation. Awarded annually, it recognizes individuals who have made outstanding contributions to science and engineering. The President receives nominations from a committee of presidential appointees based on their contributions to chemistry, engineering, computing, mathematics, and the biological, behavioral/social, and physical sciences.
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft was launched on August 3, 2004, and entered orbit about Mercury on March 17, 2011 (March 18, 2011 UTC), to begin a yearlong study of its target planet. MESSENGER's first extended mission began on March 18, 2012, and ended one year later. MESSENGER is now in a second extended mission, which is scheduled to conclude in March 2015. Dr. Sean C. Solomon, the Director of Columbia University's Lamont-Doherty Earth Observatory, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
Second of Four Planned Maneuvers Extends MESSENGER Orbital Operations - September 12, 2014
MESSENGER mission controllers at the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Md., conducted the second of four maneuvers designed to raise the spacecraft's minimum altitude sufficiently to extend orbital operations and delay the probe's inevitable impact onto Mercury's surface until early next spring.
The first of the four maneuvers, completed on June 17, raised MESSENGER to an altitude at closest approach from 115 kilometers (71.4 miles) to 156.4 kilometers (97.2 miles) above the planet's surface. Because of progressive changes to the orbit over time, the spacecraft's minimum altitude continued to decrease.
At the time of this most recent maneuver, MESSENGER was in an orbit with a closest approach of 24.3 kilometers (15.1 miles) above the surface of Mercury. With a velocity change of 8.57 meters per second (19.17 miles per hour), the spacecraft's four largest monopropellant thrusters (with a small contribution from four of the 12 smallest monopropellant thrusters) nudged the spacecraft to an orbit with a closest approach altitude of 94 kilometers (58.4 miles). This maneuver also increased the spacecraft's speed relative to Mercury at the maximum distance from Mercury, adding about 3.2 minutes to the spacecraft's eight-hour, two-minute orbit period.
This view shows MESSENGER's orientation soon after the start of the maneuver.
MESSENGER was 166.2 million kilometers (103.27 million miles) from Earth when the 2 minute, 15 second maneuver began at 11:55 a.m. EDT. Mission controllers at APL verified the start of the maneuver 9.2 minutes later, after the first signals indicating spacecraft thruster activity reached NASA's Deep Space Network tracking station outside of Madrid, Spain.
Two more maneuvers, on October 24, 2014, and January 21, 2015, will again raise the spacecraft's minimum altitude, allowing scientists to continue to collect images and data from MESSENGER's instruments.
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft was launched on August 3, 2004, and entered orbit about Mercury on March 17, 2011 (March 18, 2011 UTC), to begin a yearlong study of its target planet. MESSENGER's first extended mission began on March 18, 2012, and ended one year later. MESSENGER is now in a second extended mission, which is scheduled to conclude in March 2015. Dr. Sean C. Solomon, the Director of Columbia University's Lamont-Doherty Earth Observatory, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
Twelfth Batch of MESSENGER Data Released; Water Ice Exploration Tool Unveiled - September 5, 2014
Data collected during MESSENGER's 31st through 36th month in orbit around Mercury were released to the public today by the Planetary Data System (PDS), an organization that archives and distributes NASA's planetary mission data. With this release, data are now available to the public through the sixth full Mercury solar day of MESSENGER orbital operations.
NASA requires that all of its planetary missions archive their data in the PDS, which provides documented, peer-reviewed data to the research community. This 12th delivery of MESSENGER data extends the formatted raw and calibrated data available at the PDS for the spacecraft's science instruments and the radio science investigation to the period from September 18, 2013, to March 17, 2014. Spacecraft, planet, instrument, camera-matrix, and events (SPICE) data from launch through the period of this release are also included.
The ACT-REACT QuickMap interactive Web interface to MESSENGER data has been updated to incorporate the full coverage of the Mercury Dual Imaging System (MDIS) orbital data and the Mercury Atmospheric and Surface Composition Spectrometer (MASCS) Visible and Infrared Spectrograph (VIRS) measurements included in this delivery. QuickMap can be accessed via links on the MESSENGER websites at http://messenger.jhuapl.edu/ and http://www.nasa.gov/messenger. MDIS mosaics can be downloaded from ../Explore/Images.html#global-mosaics.
In addition, the MESSENGER team has unveiled a version of the public QuickMap interface tailored for students and educators -- the Water Ice Data Exploration (WIDE) tool. The WIDE tool highlights the sequence of data acquired over four decades, culminating in MESSENGER's observations, which led to confirmation of the proposal that water ice is present in Mercury's north polar region.
"Observations by the MESSENGER spacecraft have provided compelling support for the 20-year-old hypothesis that Mercury hosts abundant water ice and other frozen volatile materials in its permanently shadowed polar craters," said Montana State University's Keri Hallau, of MESSENGER's Education and Public Outreach team. "We wanted to create a suite of materials to engage the public in the scientific process that led to this discovery."
The WIDE suite consists of a video presentation from a mission scientist and engineer, a pencil-and-paper activity, and an introductory version of QuickMap, the interactive data-mapping tool. Each of these individual parts examines Mariner 10 flyby data from the 1970s, Earth-based radar data from the early 1990s, and MESSENGER flyby and orbital data from several instruments to show the progression of evidence in support of this conclusion. The tool is available online at http://www.messenger-education.org/teachers/wide.php.
The data for this release are available online at http://pds.nasa.gov/subscription_service/SS-20140905.html, and all of the MESSENGER data archived at the PDS are available at http://pds.nasa.gov. The team will deliver the next mission data set for release by PDS in March 2015.
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft was launched on August 3, 2004, and entered orbit about Mercury on March 17, 2011 (March 18, 2011 UTC), to begin a yearlong study of its target planet. MESSENGER's first extended mission began on March 18, 2012, and ended one year later. MESSENGER is now in a second extended mission, which is scheduled to conclude in March 2015. Dr. Sean C. Solomon, the Director of Columbia University's Lamont-Doherty Earth Observatory, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
MESSENGER Team Celebrates 10th Anniversary of Launch - August 1, 2014
Ten years ago, on August 3, 2004, NASA's MESSENGER spacecraft blasted off from Cape Canaveral, Florida, for a risky mission that would take the small satellite dangerously close to Mercury's surface, paving the way for an ambitious study of the planet closest to the Sun. The spacecraft traveled 4.9 billion miles (7.9 billion kilometers) -- a journey that included 15 trips around the Sun and flybys of Earth once, Venus twice, and Mercury three times -- before it was inserted into orbit around its target planet in 2011.
"We have operated successfully in orbit for more than three Earth years and more than 14 Mercury years as we celebrate this amazing 10th anniversary milestone," said MESSENGER Mission Operations Manager Andy Calloway, of the Johns Hopkins University Applied Physics Laboratory (APL). "The MESSENGER spacecraft operates in one of the most challenging and demanding space environments in our Solar System, and we have met that challenge directly through innovation and hard work, as exemplified by the stunning discoveries and data return achievements. Our only regret is that we have insufficient propellant to operate another 10 years, but we look forward to the incredible science returns planned for the final eight months of the mission."
MESSENGER is only the second spacecraft sent to Mercury. Mariner 10 flew past it three times in 1974 and 1975 and gathered detailed data on less than half the surface. MESSENGER took advantage of an ingenious trajectory design, lightweight materials, and miniaturization of electronics, all developed in the three decades since Mariner 10 flew past Mercury.
"It was quite challenging to design and execute a trajectory that could culminate in Mercury orbit," said Mission and Spacecraft Systems Engineer Dan O'Shaughnessy, of APL. "Designing an attendant spacecraft that was light enough to carry the necessary propellant to execute such a trajectory with enough room left over for a payload capable of global characterization of the planet is an impressive accomplishment."
Additionally, he said, "the team's concept of operations that streamlines planning while optimizing the use of our payload -- despite substantial thermal and power constraints -- is an amazing feat."
MESSENGER Deputy Principal Investigator Larry Nittler, of the Carnegie Institution of Washington, said that the mission has rewritten scientists' understanding of the planet "and given us plenty of surprises."
For instance, he said geochemical measurements have revealed a surface poor in iron, but rich in moderately volatile elements such as sulfur and sodium. "These results rule out some long-standing theories put forward to explain Mercury's anomalously high density compared with the other planets in the inner solar system," he explained. "Maps of elemental abundances show that the interior is highly chemically heterogeneous, providing important clues to the early geological history of the planet."
MESSENGER observations have also shown that Mercury's surface was shaped by volcanic activity, identified unique landforms shaped by loss of volatile materials, and confirmed the presence of large amounts of water ice protected from the Sun's heat within permanently shadowed impact craters near the planet's poles, Nittler said.
"We have found that the complex interplay of the interplanetary magnetic field with that of Mercury results in a remarkably dynamic electromagnetic environment surrounding the planet, including unexplained bursts of electrons and highly variable distributions of different elements in the thin exosphere," Nittler added. "Over the next few months, MESSENGER will observe Mercury at lower altitudes and thus smaller spatial scales than ever before, and this is sure to result both in exciting scientific discoveries and new puzzles about our solar system's enigmatic innermost planet."
In celebration of the 10th anniversary of its launch, the MESSENGER team has released a movie acquired during an early stage of MESSENGER's low-altitude campaign. The movie was assembled from 214 images taken by the narrow-angle camera (NAC) on June 8, 2014. It offers a bird's-eye view of what the spacecraft sees as it flies over the planet at close range. The NAC's field of view looked toward the horizon along the direction of MESSENGER's motion as the probe crossed the terminator into night.
"This view is what a traveler on the MESSENGER spacecraft might see during low-altitude operations in the coming year," noted MESSENGER Co-Investigator Scott Murchie of APL. "During the final phase of its mission, MESSENGER's science instruments will use low-altitude operations like this to explore the surface and subsurface of Mercury at unprecedented resolution."
The image frames were taken once per second while MESSENGER was at altitudes ranging from 115 to 165 kilometers, traveling at a speed of 3.7 kilometers per second relative to the surface. The movie is sped up by a factor of six for ease of viewing. The images have resolutions ranging from 21 to 45 meters/pixel. Higher-resolution images of Mercury's surface are possible if the camera is pointed directly below the spacecraft rather than looking to the horizon, and such operations will be the routine approach for low-altitude imaging in the coming year.
The movie starts in the far north, east of the large crater GaudÃ, passes over two unnamed craters just north of the crater Yoshikawa, over the large impact basin Lismer, north of the crater Van Dijck, and ends in the plains between the craters Nizami and Jókai. Many craters in this polar region are believed to host water ice in their permanently shadowed interiors.
This figure highlights the flight path of MESSENGER during its acquisition of images used in the flyover movie. This mosaic provides a close-up view, at 50 meters/pixel, of the surface MESSENGER imaged for the creation of the flyer video.
"Our spacecraft team is delighted to celebrate the 10th anniversary of MESSENGER's launch," adds MESSENGER Principal Investigator Sean Solomon, of Columbia University's Lamont-Doherty Earth Observatory. "In the past decade, observations by our resilient probe have deepened our understanding of both rocky planets and the dynamics of the inner heliosphere. As the new video demonstrates, however, some of the most exciting observations from the mission are still to come. We can expect new surprises as we view the innermost planet and its environment from closer range than ever before achieved by spacecraft."
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft was launched on August 3, 2004, and entered orbit about Mercury on March 17, 2011 (March 18, 2011 UTC), to begin a yearlong study of its target planet. MESSENGER's first extended mission began on March 18, 2012, and ended one year later. MESSENGER is now in a second extended mission, which is scheduled to conclude in March 2015. Dr. Sean C. Solomon, the Director of Columbia University's Lamont-Doherty Earth Observatory, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
MESSENGER Gets Closer to Mercury than Ever Before - July 28, 2014
On July 25, MESSENGER moved closer to Mercury than any spacecraft has before, dropping to an altitude at closest approach of only 100 kilometers (62 miles) above the planet's surface.
"The science team is implementing a remarkable campaign that takes full advantage of MESSENGER's orbital geometry, and the spacecraft continues to execute its command sequences flawlessly as the 14th Mercury year of the orbit phase comes to a close," said MESSENGER Mission Operations Manager Andy Calloway, of the Johns Hopkins University Applied Physics Laboratory (APL).
The latest observational campaign includes closer looks at polar ice deposits, unusual geological features, and the planet's gravity and magnetic fields "in ways that have never been possible," said APL's Ralph McNutt, MESSENGER's Project Scientist. "This dip in altitude is allowing us to see Mercury up close and personal for the first time."
Because of progressive changes to the orbit over time, MESSENGER's minimum altitude will continue to decrease. On August 19, the minimum altitude will be cut in half, to 50 kilometers. Closest approach will be halved again to 25 kilometers on September 12, noted MESSENGER Mission Design Lead Engineer Jim McAdams, also of APL.
"Soon after reaching 25 kilometers above Mercury, an orbit-correction maneuver (OCM-10) will raise this minimum altitude to about 94 kilometers," he said. "Two more maneuvers, on October 24 and January 21, 2015, will raise the minimum altitude sufficiently to delay the inevitable -- impact onto Mercury's surface -- until March 2015."
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft was launched on August 3, 2004, and entered orbit about Mercury on March 17, 2011 (March 18, 2011 UTC), to begin a yearlong study of its target planet. MESSENGER's first extended mission began on March 18, 2012, and ended one year later. MESSENGER is now in a second extended mission, which is scheduled to conclude in March 2015. Dr. Sean C. Solomon, the Director of Columbia University's Lamont-Doherty Earth Observatory, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
MESSENGER and STEREO Measurements Open New Window Into High-Energy Processes on the Sun - July 9, 2014
Understanding the Sun from afar isn't easy. How do you figure out what powers solar flares -- the intense bursts of radiation coming from the release of magnetic energy associated with sunspots -- when you must rely on observing only the light and particles that make their way to Earth's orbit? One answer: you get closer.
NASA's MESSENGER spacecraft -- which orbits Mercury, and so is as close as 28 million miles from the Sun versus Earth's 93 million miles -- is close enough to the Sun to detect solar neutrons that are created in solar flares. The average lifetime for one of these neutrons is only 15 minutes. How far they travel into space depends on their speed, and slower neutrons don't travel far enough to be seen by particle detectors in orbit around Earth. Results showing that MESSENGER has likely observed solar neutrons appeared in the Journal of Geophysical Research: Space Physics today.
"To understand all the processes on the Sun we look at as many different particles coming from the Sun as we can -- photons, electrons, protons, neutrons, gamma rays -- to gather different kinds of information," said David Lawrence, first author of the paper at The Johns Hopkins University Applied Physics Laboratory in Laurel, Md. "Closer to Earth we can observe charged particles from the Sun, but analyzing them can be a challenge as their journey is affected by magnetic fields."
Such charged particles twirl and gyrate around the magnetic field lines created by the vast magnetic systems that surround the Sun and Earth. Neutrons, however, because they are not electrically charged, travel in straight lines from the flaring region and can carry information about flare processes unperturbed by the environment through which they move. Information provided by neutrons can be used by scientists to decipher one aspect of the complicated acceleration processes that are responsible for the creation of solar energetic particles.
Lawrence and his team looked at MESSENGER data from June 4 and 5, 2011, corresponding to flares that were also accompanied by energetic charged particles. The flare occurred on the far side of the Sun so that Earth-based views of the flare region could not be obtained. However, a solar telescope on the STEREO spacecraft did have a clear view of the far-side flare region and provided critical observations of the flare. This combined use of NASA mission data makes each individual mission more effective in addressing unsolved science questions.
The scientists observed an increase in the number of neutrons at Mercury's orbit hours before the large number of accelerated charged particles reached the spacecraft. This neutron arrival time combined with other information indicated that the neutrons were most likely from the Sun and produced by accelerated flare particles striking the lower solar atmosphere. Such high-energy collisions can break apart heavy ions and release neutrons. MESSENGER and STEREO data can thus provide new information about how particles are accelerated in solar flares.
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft was launched on August 3, 2004, and entered orbit about Mercury on March 17, 2011 (March 18, 2011 UTC), to begin a yearlong study of its target planet. MESSENGER's first extended mission began on March 18, 2012, and ended one year later. MESSENGER is now in a second extended mission, which is scheduled to conclude in March 2015. Dr. Sean C. Solomon, the Director of Columbia University's Lamont-Doherty Earth Observatory, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
MESSENGER Modifies Orbit to Prepare for Low-Altitude Campaign - June 17, 2014
MESSENGER successfully completed the first orbit-correction maneuver of its Second Extended Mission this morning to raise its minimum altitude above Mercury from 113.9 kilometers (70.8 miles) to 155.1 kilometers (96.4 miles). This maneuver is the first of four designed to modify the spacecraft's orbit around Mercury so as to delay the spacecraft's inevitable impact onto Mercury's surface and allow scientists to continue to gather novel information about the innermost planet.
During the primary phase of the MESSENGER mission, the spacecraft's orbit around Mercury was highly eccentric, drifting between 200 and 500 kilometers (124 to 311 miles) above Mercury's surface at closest approach, and between 15,200 and 14,900 kilometers (9,445 to 9,258 miles) above the surface at its farthest point, and completing an orbit every 12 hours. Spacecraft operators at the Johns Hopkins Applied Physics Laboratory (APL) in Laurel, Maryland, conducted several spacecraft maneuvers to counter the perturbing forces that caused MESSENGER's lowest orbital altitude to drift upward, away from its preferred observing geometry, and early in MESSENGER's First Extended Mission conducted a pair of maneuvers to reduce the orbital period to eight hours.
"In this final phase of the mission, the opposite effect is happening," explained the mission trajectory lead Jim McAdams of APL. "To extend the mission, we need to raise the minimum altitude by increasing the Mercury-relative speed of the spacecraft when it is farthest from Mercury."
For this latest orbit adjustment, MESSENGER was 82.9 million kilometers (51.5 million miles) from Earth and 69.8 million kilometers (43.3 million miles) from the Sun. The 3.2-minute-long maneuver -- which used two of the four largest monopropellant thrusters, with a small contribution from four of the 12 smallest monopropellant thrusters -- began at about 10:53 a.m., EDT. APL mission controllers verified the start of the maneuver 4.6 minutes later, when the first signals indicating spacecraft thruster activity reached MESSENGER's Mission Operations Center via NASA's Deep Space Network tracking station outside of Madrid, Spain.
"MESSENGER's results to date have revolutionized our knowledge of Mercury's global geology, the nature of volcanism across the surface, the cratering record, and the history of the planet's contraction, and they have also revealed unexpected discoveries, such as hollows," said APL's Nancy Chabot, who chairs MESSENGER's Geology Discipline Group. During the remainder of MESSENGER's mission, the focus of geological observations will narrow from a global perspective to views of selected areas in unprecedented detail, she explained.
"With the low-altitude imaging campaign, MESSENGER will acquire the highest-resolution images ever obtained of Mercury, enabling us to search for volcanic flow fronts, small-scale tectonic features, layering in crater walls, locations of impact melt, and new aspects of hollows. Those detailed views will provide a new understanding of Mercury's geological evolution," she said.
The measurement resolution of Mercury's gravity and internal magnetic fields improves markedly as the altitude of the MESSENGER spacecraft decreases. "This improvement means that smaller-scale and weaker-amplitude features can be mapped, and in the case of magnetic measurements, the external and internal fields can be separated with greater fidelity," said Roger Phillips of the Southwest Research Institute in Boulder, Colorado.
"MESSENGER will continue its downward march, interrupted by the final three orbit-correction maneuvers, but also achieving altitudes lower than 50 kilometers for the first time," said Phillips, who chairs MESSENGER's Geophysics Discipline Group. "For the magnetic field, the question of whether the crust has retained an ancient, frozen-in (remanent) magnetic field, as have Mars and Earth, can be answered, and a higher-resolution picture of the field generated by Mercury's liquid outer core can be obtained. For the gravity field, the signatures of large fold-and-thrust belts and of impact craters will shed light on the structure of the crust and the early history of Mercury."
MESSENGER's geochemical measurements obtained during the upcoming months will provide measurements with vastly improved spatial resolution, according to APL's Patrick Peplowski, the instrument scientist for the Gamma-Ray and Neutron Spectrometer. "Not only will the low-altitude campaign help our overall efforts to map Mercury's surface composition with the best possible spatial resolution, we will now be able to obtain spatially resolved measurements of features that were previously too small to resolve with the geochemical instruments," he said. "For example, we have opportunities to study the chemical composition of pyroclastic deposits and the mysterious low-reflectance material. We are also hoping to spatially resolve individual ice-hosting craters for the first time."
Even with today's maneuver, the spacecraft's altitude at closest approach will continue to decrease until raised by additional maneuvers in September and October of this year and January 2015. At that point, MESSENGER will have spent its accessible propellant, and additional altitude-changing maneuvers will not be possible. In March 2015, the spacecraft will impact the surface of Mercury, having successfully completed four years in orbit about Mercury.
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft was launched on August 3, 2004, and entered orbit about Mercury on March 17, 2011 (March 18, 2011 UTC), to begin a yearlong study of its target planet. MESSENGER's first extended mission began on March 18, 2012, and ended one year later. MESSENGER is now in a second extended mission, which is scheduled to conclude in March 2015. Dr. Sean C. Solomon, the Director of Columbia University's Lamont-Doherty Earth Observatory, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
On April 20, MESSENGER completed its 3,000th orbit of Mercury and moved closer to the planet than any spacecraft has been before, dropping to an altitude of 199 kilometers (123.7 miles) above the planet's surface.
"We are cutting through Mercury's magnetic field in a different geometry, and that has shed new light on the energetic electron population," said MESSENGER Project Scientist Ralph McNutt, of the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Md. "In addition, we are now spending more time closer to the planet in general -- and that has, in turn, increased the opportunities for all of the remote sensing instruments to make higher-resolution observations of the planet."
MESSENGER has been completing three orbits of Mercury every day since April 2012, when two orbit-correction maneuvers reduced its orbital period about Mercury from 12 hours to 8 hours. The shorter orbit has allowed the science team to explore new questions about Mercury's composition, geological evolution, and environment that were raised by discoveries made during the first year of orbital operations.
APL's Carolyn Ernst, the deputy instrument scientist for the Mercury Laser Altimeter (MLA), said the change from a 12- to an 8-hour orbit provided her team with 50% more altimetry tracks. "MLA coverage takes a long time to build up, and because of the small footprint of the laser, a lot of coverage is needed to obtain good spatial resolution. The more data we acquire, the better we resolve the topography of the planet," she said. "The 8-hour orbit has also allowed us to make more MLA reflectivity measurements, which have provided critical clues for characterizing Mercury's radar-bright deposits at high northern latitudes."
The probe has been edging closer and closer to Mercury since March 2013, at about the time that the spacecraft orbit's minimum altitude passed closest to Mercury's north pole.
APL's David Lawrence, a MESSENGER Participating Scientist, said he is excited about what the low-altitude orbits will reveal about Mercury's surface composition. "To date our compositional measurements with neutron, X-ray, and gamma-ray data have resolved only very large regions on Mercury's surface. Altitudes of less than 100 kilometers will enable us to pinpoint the compositional signatures of specific geologic features, which in turn will help us to understand how the surface formed and has changed over time."
MESSENGER's periapsis altitude will continue to decrease until the first orbit-correction maneuver of the low-altitude campaign, scheduled for June 17.
"The final year of MESSENGER's orbital operations will be an entirely new mission," added MESSENGER Principal Investigator Sean Solomon, of Columbia University's Lamont-Doherty Earth Observatory. "With each orbit, our images, our surface compositional measurements, and our observations of the planet's magnetic and gravity fields will be higher in resolution than ever before. We will be able to characterize Mercury's near-surface particle environment for the first time. Mercury has stubbornly held on to many of its secrets, but many will at last be revealed."
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft was launched on August 3, 2004, and entered orbit about Mercury on March 17, 2011 (March 18, 2011 UTC), to begin a yearlong study of its target planet. MESSENGER's first extended mission began on March 18, 2012, and ended one year later. MESSENGER is now in a second extended mission, which is scheduled to conclude in March 2015. Dr. Sean C. Solomon, the Director of Columbia University's Lamont-Doherty Earth Observatory, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
Team Celebrates Orbital Anniversary, Reports on New Findings at Planetary Conference - March 17, 2014
Today, the MESSENGER team celebrates the third anniversary of the probe's Mercury orbit insertion. On March 17, 2011 (Eastern Daylight Time), the spacecraft made history when it became the first probe to orbit the innermost planet. Over the last three years, MESSENGER instruments have fully mapped Mercury's surface and yielded discoveries that have changed views on how the inner planets formed and evolved.
The latest findings will be described in 25 papers presented this week at the 45th Lunar and Planetary Science Conference in The Woodlands, Texas. Now -- as a key part of MESSENGER's second extended mission -- the team is preparing to embark on a low-altitude imaging campaign that promises to reveal even more information about Mercury.
The altitude of the spacecraft at closest approach has been slowly decreasing as the Sun's gravity perturbs its orbit around Mercury, and the progressively closer approaches will provide MESSENGER's instruments with an unprecedented opportunity to make high-resolution observations of the planet. For example, the hollows first revealed by the probe's instruments in 2011 are suspected to have formed because volatile elements sublime off the surface, but observations to date could not confirm this hypothesis.
At spacecraft altitudes below 350 kilometers, the Mercury Dual Imaging Instrument's Narrow Angle Camera will acquire images with pixel scales ranging from 20 meters to as little as 2 meters. Such high-resolution images will reveal small features of the enigmatic hollows for the first time. "We will be seeing features at up to 10 times the resolution of the images acquired so far," noted MESSENGER Co-Investigator Scott Murchie of the Johns Hopkins University Applied Physics Laboratory (APL).
"Our spacecraft team is delighted to celebrate the third anniversary of MESSENGER's orbit insertion at Mercury," adds MESSENGER Principal Investigator Sean Solomon, of Columbia University's Lamont-Doherty Earth Observatory. "However, some of the most exciting observations from the mission are still to come. We can expect new surprises as we view the innermost planet from closer range than ever before achieved by spacecraft."
The lowest point of MESSENGER's orbit is now 226 kilometers (140.4 miles) above Mercury's surface. This minimum altitude will continue to decrease until the first maneuver of the mission's low-altitude campaign in mid-June 2014. Following the maneuver, the spacecraft's altitude at closest approach will continue to decrease until raised by additional maneuvers in September 2014, October 2014, and January 2015. At that point, MESSENGER will have spent its onboard fuel, and additional maneuvers to raise the minimum altitude will not be possible. In March 2015, the spacecraft will impact the surface of Mercury, having successfully completed four years in orbit about Mercury.
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft was launched on August 3, 2004, and entered orbit about Mercury on March 17, 2011 (March 18, 2011 UTC), to begin a yearlong study of its target planet. MESSENGER's first extended mission began on March 18, 2012, and ended one year later. MESSENGER is now in a second extended mission, which is scheduled to conclude in March 2015. Dr. Sean C. Solomon, the Director of Columbia University's Lamont-Doherty Earth Observatory, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
Mercury's Contraction Much Greater Than Thought - March 16, 2014
New global imaging and topographic data from MESSENGER show that the innermost planet has contracted far more than previous estimates. The results are based on a global study of more than 5,900 geological landforms, such as curving cliff-like scarps and wrinkle ridges, that have resulted from the planet's contraction as Mercury cooled. The findings, published online today in Nature Geoscience, are key to understanding the planet's thermal, tectonic, and volcanic history, and the structure of its unusually large metallic core.
Unlike Earth, with its numerous tectonic plates, Mercury has a single rigid, top rocky layer. Prior to the MESSENGER mission only about 45% of Mercury's surface had been imaged by spacecraft. Old estimates, based on this non-global coverage, suggested that the planet had contracted radially by about 1/2 to 2 miles (0.8 to 3 kilometers), substantially less than that indicated by models of the planet's thermal history. Those models predicted a radial contraction of about 3 to 6 miles (5 to 10 kilometers) starting from the late heavy bombardment of the Solar System, which ended about 3.8 billion years ago.
The new results, which are based on the first comprehensive survey of the planet's surface, show that Mercury contracted radially by as much as 4.4 miles (7 kilometers) -- substantially more than the old estimates, but in agreement with the thermal models. Mercury's modern radius is 1,516 miles (2,440 kilometers).
"These new results resolved a decades-old paradox between thermal history models and estimates of Mercury's contraction," remarked Paul Byrne, a planetary geologist and MESSENGER Visiting Investigator at the Carnegie Institution of Washington. "Now the history of heat production and loss and global contraction are consistent. Interestingly, our findings are also reminiscent of now-obsolete models for how large-scale geological deformation occurred on Earth when the scientific community thought that the Earth only had one tectonic plate. Those models were developed to explain mountain building and tectonic activity in the nineteenth century, before plate tectonics theory."
Byrne and his co-authors identified a much greater number and variety of geological structures on the planet than had been recognized in previous research. They identified 5,934 ridges and scarps attributed to global contraction, which ranged from 5 to 560 miles (9 to 900 kilometers) in length.
The researchers used two complementary techniques to estimate the contraction from their global survey of structures. Although the two estimates of radius change differed by 0.6 to 1 mile (1 to 1.6 kilometers), both were substantially greater than old estimates.
"I became interested in the thermal evolution of Mercury's interior when the Mariner 10 spacecraft sent back images of the planet's great scarps in 1974-75, but the thermal history models predicted much more global contraction than the geologists inferred from the scarps then observed, even correcting for the fact that Mariner 10 imaged less than half of Mercury's surface," noted MESSENGER Principal Investigator Sean Solomon, of Columbia University's Lamont-Doherty Earth Observatory. "This discrepancy between theory and observation, a major puzzle for four decades, has finally been resolved. It is wonderfully affirming to see that our theoretical understanding is at last matched by geological evidence."
This image shows a long collection of ridges and scarps on the planet Mercury called a fold-and-thrust belt. The belt stretches over 336 miles (540 km). The colors correspond to elevation -- yellow-green is high and blue is low. Contact Paul Byrne at pbyrne@carnegiescience.edu, or (281) 486-2140.
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft was launched on August 3, 2004, and entered orbit about Mercury on March 17, 2011 (March 18, 2011 UTC), to begin a yearlong study of its target planet. MESSENGER's first extended mission began on March 18, 2012, and ended one year later. MESSENGER is now in a second extended mission, which is scheduled to conclude in March 2015. Dr. Sean C. Solomon, the Director of Columbia University's Lamont-Doherty Earth Observatory, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
NASA requires that all of its planetary missions archive their data in the PDS, which provides well-documented, peer-reviewed data to the research community. The latest release of MESSENGER measurements includes raw and calibrated products created from data acquired through September 17, 2013, and advanced products created from data acquired through March 17, 2013.
"Delivery 11 has the largest volume of data -- over three terabytes -- in a single MESSENGER delivery to date," notes MESSENGER's Science Operations Center lead Susan Ensor, of the Johns Hopkins University Applied Physics Laboratory (APL). "The size of MESSENGER's deliveries will continue to grow as we add new products, continue to archive extended mission orbital data, and deliver final products at the end of the mission."
This release includes new raw and calibrated data products from the Gamma-Ray Spectrometer (GRS) anti-coincidence shield acquired after an update to the GRS instrument flight software. The update followed the failure in June 2012 of the cryogenic cooler for the germanium detector. With that failure, the GRS could no longer acquire gamma-ray spectra, so the shield was repurposed as a neutron and electron detector. The new products in this delivery include improved neutron spectra from the shield and new high-time-cadence measurements designed to characterize energetic electron events at unprecedented time resolution.
This release includes a new global, three-color map produced with images acquired by MESSENGER's Mercury Dual Imaging System (MDIS), and, for the first time, image backplanes with latitude and longitude, as well as incidence, emission, and phase angles.
"The global color maps of Mercury are intended to provide a uniform view of the planet's surface, so differences in lithology and stratigraphy can be analyzed easily," said APL's Mary Keller, a remote sensing scientist on the MESSENGER team. "The three-color map uses a subset of the bands that were combined into the eight-color map and provides a higher-resolution view of surface features for comparison."
Also now available are reflectance spectra and a 750-nm base map derived from data from the Mercury Atmospheric and Surface Composition Spectrometer (MASCS) Visible and Infrared Spectrograph (VIRS), and an exosphere model derived from the MASCS Ultraviolet and Visible Spectrometer (UVVS).
"VIRS captures many wavelengths of light from a single spot on the surface at a time, creating a spectral profile of the surface as MESSENGER orbits Mercury," explains APL's Noam Izenberg, the MASCS Instrument Scientist. "The VIRS sensor on MASCS has accumulated several million individual spectra, enough that the reflectance of the surface can be interpolated to reveal surface brightness details similar to those seen in the MDIS base map. Both of these instruments probe the spectral 'fingerprint' of rocks on Mercury's surface in different ways, enabling scientists to map the compositional and physical variations of surface rocks by observing how light interacts with them."
An improved-resolution digital elevation model for Mercury's northern hemisphere has also been made available in this release. "The newest Mercury Laser Altimeter digital elevation model now includes full coverage of the north polar region, an important milestone for the mission," says APL's Carolyn Ernst, the instrument sequencer for MLA. "Additionally, this product has substantially higher spatial resolution (500 meters per pixel) than those previously delivered to the PDS and reveals incredible detail, including wrinkle ridges, ghost craters, central peaks, and crater chains."
The ACT-REACT QuickMap interactive Web interface to MESSENGER data has been updated to incorporate the full coverage of the MDIS and MASCS VIRS orbital data included in this release. QuickMap can be accessed via links on the MESSENGER websites at http://messenger.jhuapl.edu/ and http://www.nasa.gov/messenger. The MDIS mosaics can be downloaded from ../Explore/Images.html#global-mosaics.
The data for this release are available online at http://pds.nasa.gov/subscription_service/SS-20140307.html, and all of the MESSENGER data archived at the PDS are available at http://pds.nasa.gov. The team will deliver the next mission data set for release by PDS in September.
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft was launched on August 3, 2004, and entered orbit about Mercury on March 17, 2011 (March 18, 2011 UTC), to begin a yearlong study of its target planet. MESSENGER's first extended mission began on March 18, 2012, and ended one year later. MESSENGER is now in a second extended mission, which is scheduled to conclude in March 2015. Dr. Sean C. Solomon, the Director of Columbia University's Lamont-Doherty Earth Observatory, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
The National Space Society has selected NASA's MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) mission as the 2014 recipient of the Space Pioneer Award in the Science and Engineering category. "With this award, NSS recognizes both the importance of the first dedicated probe to orbit Mercury and the significance of the scientific results already released," the organization said in announcing the award.
The annual Space Pioneer awards recognize individuals and teams whose accomplishments have helped to open the space frontier. The awards are divided into 13 categories with the intent of recognizing those who have made significant contributions in different fields of endeavor to "develop a space faring civilization that will establish communities beyond the Earth." Because NSS typically selects three Space Pioneer award recipients each year, not every category is awarded.
"The historic achievements of the MESSENGER Team (after construction and launch of the spacecraft) include successfully placing the spacecraft accurately into its intended orbit around Mercury on March 18, 2011, after a series of six critical flybys of the Earth, Venus, and Mercury itself," NSS said. "Besides the critical contribution of accurately mapping Mercury's surface, the science results have confirmed the presence of water ice and organic chemicals at the poles, and the fact that Mercury's magnetic field is offset to the north substantially from its equator."
"The MESSENGER team is deeply honored to receive this recognition from the National Space Society," said MESSENGER Principal Investigator Sean Solomon of Columbia University. "Our engineers have met the profound challenges of inserting a spacecraft into orbit about Mercury and operating for years in the harsh environment of the inner solar system. And that vantage has permitted MESSENGER to make a series of discoveries that are changing our views on how the inner planets formed and evolved. All of us on the MESSENGER team count ourselves as extraordinarily fortunate to have been along for the exhilarating ride."
The award will be presented at the International Space Development Conference in Los Angeles, which runs from May 14-18, 2014.
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft was launched on August 3, 2004, and entered orbit about Mercury on March 17, 2011 (March 18, 2011 UTC), to begin a yearlong study of its target planet. MESSENGER's first extended mission began on March 18, 2012, and ended one year later. MESSENGER is now in a second extended mission, which is scheduled to conclude in March 2015. Dr. Sean C. Solomon, the Director of Columbia University's Lamont-Doherty Earth Observatory, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
MESSENGER Surpasses 200,000 Orbital Images of Mercury - February 6, 2014
MESSENGER has now returned more than 200,000 images acquired from orbit about Mercury. The 1996 proposal for the mission promised a return of at least 1,000 images says Robert Gold, MESSENGER's Science Payload Manager. "We expected then that we would have some data compression that would probably raise the image total to somewhere near 2,000 images," says Gold, of the Johns Hopkins University Applied Physics Laboratory (APL), but scientists did not imagine then the degree to which MESSENGER would surpass that goal.
"Returning over 200,000 images from orbit about Mercury is an impressive accomplishment for the mission, and one I've been personally counting down for the last few months," says APL's Nancy Chabot, the Instrument Scientist for the Mercury Dual Imaging System (MDIS). "However, I'm really more excited about the many thousands of images that are still in MESSENGER's future, especially those that we plan to acquire at low altitudes and will provide the highest resolution views yet of Mercury's surface."
During MESSENGER's second extended mission, the spacecraft is making a progressively closer approach to Mercury's surface with each successive orbit. In about two months, each closest approach will be at a lower altitude than at any previous point in the mission, enabling the acquisition of unprecedentedly high-spatial-resolution data. For spacecraft altitudes below 350 kilometers, Narrow Angle Camera (NAC) images will be acquired with pixel scales ranging from 20 meters to as little as 2 meters.
To commemorate the milestone, image scientists released this four-image mosaic -- one of the first from the MDIS low-altitude imaging campaign -- that reveals, among other features, hollows that appear to have formed in one layer in the wall of this 15-kilometer-diameter crater.
The mission marks three additional milestones today: the spacecraft concludes its 12th Mercury year in orbit, its 18th Mercury sidereal day in orbit, and its 6th Mercury solar day in orbit.
"We have come an incredible way since the first mission proposal was submitted to NASA just over 17 years ago," notes MESSENGER Project Scientist Ralph McNutt of APL. "Getting to launch and then to Mercury, flyby by flyby, and into orbital operations were incredible accomplishments -- against all sorts of odds -- and yet we are now, almost routinely, noting these statistics about the mission that has literally revealed an entirely new world to humanity."
When MESSENGER was launched in August 2004, he continues, "none of the team in their wildest imagination could have foreseen the successes that we now celebrate with new data coming back week by week from the innermost planet. And we are not done. With a little more than a year left to go, before gravity brings the end to operations, we will view the planet and its environment from altitudes lower than were ever envisioned only a few short years ago -- and, as with any planetary mission providing closer and closer looks at a planetary neighbor, all we can guess is that we have not wrung all of Mercury's surprises and discoveries just yet."
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and entered orbit about Mercury on March 17, 2011 (March 18, 2011 UTC), to begin a yearlong study of its target planet. MESSENGER's first extended mission began on March 18, 2012, and ended one year later. MESSENGER is now in a second extended mission, which is scheduled to conclude in March 2015. Dr. Sean C. Solomon, the Director of Columbia University's Lamont-Doherty Earth Observatory, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
MESSENGER Team Members Honored for Outstanding Accomplishments in Scientific Research and Education and Public Outreach - December 31, 2013
Three members of the MESSENGER team have been honored this month for their accomplishments in planetary research and education and public outreach. The three honorees are Catherine Johnson from the University of British Columbia (UBC) and the Planetary Science Institute, Ryan Dewey from the University of Colorado, and Brian Grigsby from Shasta High School in Redding, California.
Johnson was one of 62 scientists elected this year as a Fellow of the American Geophysical Union (AGU). The designation as Fellow, which recognizes researchers who have made exceptional contributions to Earth and space sciences, is bestowed on not more than 0.1 percent of AGU members in any given year. Johnson and other new Fellows were honored on December 11 at the AGU Fall Meeting in San Francisco.
Johnson, a MESSENGER Participating Scientist, was recognized for her studies of planetary magnetism on Earth, Mars, and Mercury, and for her work on the tectonics and gravitational fields of the inner planets. She is a Co-Investigator on NASA's InSight mission that will place a geophysical lander on Mars to study its deep interior, a Co-Investigator on the OSIRIS REx mission that will map asteroid Bennu, and a Professor of Planetary Geophysics in the Department of Earth, Ocean and Atmospheric Sciences at UBC in Vancouver.
Dewey, an undergraduate majoring in astronomy and physics at the University of Colorado, Boulder, and a Research Assistant in the university's Laboratory for Atmospheric and Space Physics, received an Outstanding Student Paper Award from AGU. Those awards are given to promote, recognize, and reward undergraduate, master's, and doctoral students for innovative research in the geophysical sciences. Dewey was recognized for his paper given at the AGU Fall Meeting on "WSA-ENLIL Cone Extension: Improving Solar Wind Forcing Parameter Estimates at Mercury."
Dewey works with MESSENGER Co-Investigator Daniel Baker on the interactions between Mercury's magnetosphere and its space environment. His award-winning paper focused on improving representations for the local space environment at Mercury. "Mercury has a much weaker intrinsic magnetic field and is much closer to the Sun than Earth, so the space environment plays a larger role in plasma processes in Mercury's magnetosphere," Dewey said. "This space environment includes both the background solar wind and transient solar eruptions. Previous estimates of this environment have combined MESSENGER observations with the WSA-ENLIL model, but this approach included only the background solar wind."
The Cone extension to WSA-ENLIL simulates transient events, providing a more complete approach, he explained. "My paper compared the results for the WSA-ENLIL model with and without the Cone extension. We found that the Cone extension improves the accuracy of the space environment estimates. More specifically, the Cone extension allows us to better model specific transient events that arrive at Mercury, and it improves 'effectiveness' indicators such as electron event count rates. Our results yield generally valid, continuous inputs of the space environment for studies of Mercury's magnetosphere, exosphere, and surface."
Grigsby was selected this month by the National Space Club as the 2014 recipient of the National Space Educator Award. His award will be presented on March 7, 2014, at the 57th Annual Robert H. Goddard Memorial Dinner at the Washington Hilton Hotel in Washington, D.C. Since 1982, this award has been given annually to secondary school teachers who mentor students in the field of space, science, and technology. Recipients are also given a $1,500 grant and a plaque for their respective school.
Grigsby is the science department chair at Shasta High School and the coordinator of MESSENGER's Student Planetary Investigator Program. In that program, students -- with the assistance of science mentors -- are given an opportunity to add to the body of data on Mercury by performing research on the planet's anomalous density, its geologic history, its magnetic field, its core, the unusual materials at Mercury's poles, and other volatiles found on the surface.
Grigsby was previously the director of the Arizona State University (ASU) Mars Education and Outreach Program within the Mars Space Flight Facility at ASU's School of Earth and Space Exploration. While at ASU, he created a new standards-based curriculum that allows educators nationwide to be involved in the exploration of Mars while continuing to meet their educational objectives.
"It is wonderful that AGU and the National Space Club have recognized the exceptional contributions of Catherine, Ryan, and Brian," said MESSENGER Principal Investigator Sean Solomon of Columbia University. "All of us on the MESSENGER team are proud to be working with these outstanding colleagues."
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and entered orbit about Mercury on March 17, 2011 (March 18, 2011 UTC), to begin a yearlong study of its target planet. MESSENGER's first extended mission began on March 18, 2012, and ended one year later. MESSENGER is now in a second extended mission, which is scheduled to conclude in March 2015. Dr. Sean C. Solomon, the Director of Columbia University's Lamont-Doherty Earth Observatory, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
Beatles Legend, Antiwar Author among Those Honored by Newly Named Mercury Craters - December 19, 2013
The International Astronomical Union (IAU) -- the arbiter of planetary and satellite nomenclature since its inception in 1919 -- recently approved a proposal from the MESSENGER Science Team to assign names to 10 impact craters on Mercury. In keeping with the established naming theme for craters on Mercury, all of the newly designated features are named after "deceased artists, musicians, painters, and authors who have made outstanding or fundamental contributions to their field and have been recognized as art historically significant figures for more than 50 years."
The newly named craters are
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and entered orbit about Mercury on March 17, 2011 (March 18, 2011 UTC), to begin a yearlong study of its target planet. MESSENGER's first extended mission began on March 18, 2012, and ended one year later. MESSENGER is now in a second extended mission, which is scheduled to conclude in March 2015. Dr. Sean C. Solomon, the Director of Columbia University's Lamont-Doherty Earth Observatory, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
MESSENGER Celebrates 1,000 Earth Days in Orbit around Mercury - December 11, 2013
Later today, the MESSENGER spacecraft will have completed 1,000 Earth days of flight operations in orbit around Mercury. "This milestone is a testament to the outstanding work of those who designed, tested, and operated this spacecraft," says Jim McAdams of the Johns Hopkins University Applied Physics Laboratory (APL) and the lead engineer for MESSENGER's mission design team.
"MESSENGER was designed to function for eight years following launch and to withstand the harsh environmental conditions of the inner solar system and solar heating up to 11 times greater than experienced by spacecraft near Earth," McAdams says. "The probe not only has continued to function, it has thrived, with very little loss of planned observations for more than nine years and four months since launch."
"To date, the spacecraft has returned 198,166 images from orbit about Mercury, far exceeding the mission's original plans," says APL's Rob Gold, MESSENGER's Science Payload Manager. "In the original mission concept we were planning to use half of the telemetry for images and the rest for the other instruments, and that plan would have returned about 1,000 images of the surface of Mercury. That we are now approaching 200,000 images is the result of major technological improvements made during construction of MESSENGER."
"Some of the improvements were in the hardware," he noted, "including the development of an electrically steered phased-array antenna. Others were in operational techniques, such as the use of the CCSDS (Consultative Committee for Space Data Systems) File Delivery Protocol," a highly specialized protocol designed to overcome space operations communications challenges.
The orbital phase of the MESSENGER mission, which was originally designed to last one Earth year, is now nine months into a second extended mission that is scheduled to conclude early in 2015. The lowest point of MESSENGER's orbit is now 325 kilometers (201 miles) above Mercury's surface. This minimum altitude will continue to decrease until the first maneuver of the mission's low-altitude campaign in mid-June 2014.
"MESSENGER has not merely survived life in a tough neighborhood, it has produced a string of major scientific discoveries that have transformed our understanding of the innermost planet and how the inner solar system was formed," adds MESSENGER Principal Investigator Sean Solomon of Columbia University. "And we expect those discoveries to continue as MESSENGER begins to pass progressively closer to Mercury's surface than ever before."
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and entered orbit about Mercury on March 17, 2011 (March 18, 2011 UTC), to begin a yearlong study of its target planet. MESSENGER's first extended mission began on March 18, 2012, and ended one year later. MESSENGER is now in a second extended mission, which is scheduled to conclude in March 2015. Dr. Sean C. Solomon, the Director of Columbia University's Lamont-Doherty Earth Observatory, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
MESSENGER Team Presents Latest Mercury Findings at AGU Fall Meeting - December 9, 2013
Members of the MESSENGER team will present a broad range of findings from the spacecraft's orbital investigation of Mercury during the 2013 Fall Meeting of the American Geophysical Union (AGU), which takes place this week, December 9-13, in San Francisco. In 33 oral and poster presentations, team scientists will report on the analysis and interpretation of observations made by MESSENGER's instruments in the 2.5 years since the spacecraft entered orbit around Mercury in March 2011.
The majority of the MESSENGER papers will be given in three special sessions on December 9. Those oral and poster presentations will report new findings on Mercury's gravity field, surface composition, exosphere, and magnetotail; thermal models derived from MESSENGER topography; Mercury's permanently shadowed craters; and the planet's substorm cycle.
Many of these presentations will be available by video on demand. For more information, visit the AGU Fall Meeting web page http://fallmeeting.agu.org/2013/virtual-options/live-stream-video-demand/ and click on the appropriate session at the scheduled time (Pacific time).
On December 10, from 1:30 to 2:30 p.m. PDT, MESSENGER Project Scientist Ralph McNutt will present MESSENGER's preliminary findings from its observations of the comets 2P/Encke and C/2012 S1 (ISON) at a press conference, "The Battle of Fire and Ice: New Scientific Results from Comet ISON." Additional information is available at http://fallmeeting.agu.org/2013/media-center/press-conferences/#ison.
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and entered orbit about Mercury on March 17, 2011 (March 18, 2011 UTC), to begin a yearlong study of its target planet. MESSENGER's first extended mission began on March 18, 2012, and ended one year later. MESSENGER is now in a second extended mission, which is scheduled to conclude in March 2015. Dr. Sean C. Solomon, the Director of Columbia University's Lamont-Doherty Earth Observatory, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
A Tale of Two Comets: MESSENGER Captures Images of Encke and ISON - November 25, 2013
On November 18, NASA's Mercury-orbiting MESSENGER spacecraft pointed its Mercury Dual Imaging System (MDIS) at 2P/Encke and captured this image of the comet as it sped within 2.3 million miles (3.7 million kilometers) of Mercury's surface. The next day, the probe captured this companion image of C/2012 S1 (ISON), as it cruised by Mercury at a distance of 22.5 million miles (36.2 million kilometers) on its way to its late-November closest approach to the Sun.
MESSENGER's cameras have been acquiring targeted observations of Encke since October 28 and ISON since October 26, although the first faint detections didn't come until early November. During the closest approach of each comet to Mercury, the Mercury Atmospheric and Surface Composition Spectrometer (MASCS) and X-Ray Spectrometer (XRS) instruments also targeted the comets. Observations of ISON conclude on November 26, when the comet passes too close to the Sun, but MESSENGER will continue to monitor Encke with both the imagers and spectrometers through early December.
The spacecraft has a view of the comets very different from that of Earth-based observers. "MESSENGER imaged Encke only a few days before its perihelion when it was at its brightest," explains Ron Vervack, of the Johns Hopkins University Applied Physics Laboratory, who is leading MESSENGER's comet-observation campaign. "That we are so close to the comet at this time offers a chance to make important observations that could shed light on its asymmetric behavior about perihelion."
In contrast, ISON did not pass as close to Mercury, but the comet was between the Earth and Mercury when it passed closest to MESSENGER. "We saw the side opposite to that visible from Earth," says Vervack, "so our images and spectra are complementary to observations from Earth made at the same time and could aid in understanding the variable activity of the comet as it approached the Sun."
On the day that Encke was closest to Mercury, the MDIS wide-angle camera scanned the comet with all of its 12 filters while the instrument's narrow-angle camera (NAC) snapped images of the rotating comet every 10 minutes to capture a full 360-degree view. The imaging campaign for ISON was similar, with the NAC capturing a series of stills every 30 minutes.
Several ground- and space-based NASA observatories, as well as many other observatories around the world, are collecting data on the comets. However, none will be able to collect simultaneous images and spectra from X-ray through near-infrared wavelengths when the comets are so close to the Sun, as will MESSENGER. Vervack expects MESSENGER to gather 15 hours worth of data on Encke and another 25 hours on ISON. "These observations of Encke and ISON fill a gap in heliocentric coverage to which most other observatories don't have access," Vervack says.
Scientists are still combing through the data collected by MASCS, but there are already confirmed detections of several molecules and atoms, including OH, NH, CS, oxygen, carbon, sulfur, and hydrogen. "Far-ultraviolet observations can't be made from ground-based observatories, and only a few instruments in space have been able to look at the comets in the ultraviolet," says Vervack. "The MASCS observations are therefore of great interest."
Scientists were also hoping to obtain the first definitive detections of cometary X-ray emission from silicon, magnesium, and aluminum. "NASA's Chandra X-ray space telescope has observed ISON and Encke and seen X-ray emission from them both," Vervack says. "We are able to make these observations when both comets are closer to the Sun, so the X-ray emissions have the potential to be much more intense." However, a series of large solar flares during the observations increased the contaminating background in the X-ray spectra and have complicated the analysis. "We can't help what the Sun does," says Vervack, "but we're going to analyze the data carefully to see if there are any detections to be had."
Taken together, the MESSENGER observations offer a varied science investigation of the comets. "Whereas the MDIS images will provide a global picture of the comet coma morphology, MASCS observations will inform us about the composition of the cometary ices and XRS may be able to tell us what the dust is made of," Vervack says.
"Comet encounters were not considered when the MESSENGER mission was designed," adds MESSENGER Principal Investigator Sean Solomon of Columbia University. "If Encke and ISON share a few of their secrets on the formation and evolution of the Solar System, the MESSENGER team will be delighted with the scientific bonus."
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and entered orbit about Mercury on March 17, 2011 (March 18, 2011 UTC), to begin a yearlong study of its target planet. MESSENGER's first extended mission began on March 18, 2012, and ended one year later. MESSENGER is now in a second extended mission, which is scheduled to conclude in March 2015. Dr. Sean C. Solomon, the Director of Columbia University's Lamont-Doherty Earth Observatory, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
MESSENGER Detects Comets ISON and Encke, Prepares for Closer Encounters - November 14, 2013
NASA's Mercury-orbiting MESSENGER spacecraft has captured images of two comets -- 2P/Encke and C/2012 S1 (ISON) -- setting the stage for observations later this month when both comets will be substantially brighter and much closer to Mercury and the Sun.
ISON was discovered in September 2012 by amateur Russian astronomers, who observed with a 16-inch telescope that is part of the International Scientific Optical Network (ISON), after which the comet was named. On November 28, ISON will fly within 700,000 miles (1.2 million kilometers) of the Sun's photosphere, at which time it is expected either to flare brilliantly or disintegrate.
As part of an ISON observation campaign involving ground- and space-based NASA observatories, as well as many other observatories around the world, MESSENGER has been poised for several weeks to collect observations of ISON. From November 9 through November 11, the probe's Mercury Dual Instrument System (MDIS) captured its first images of the comet.
"We are thrilled to see that we've detected ISON," said Ron Vervack, of the Johns Hopkins University Applied Physics Laboratory, who is leading MESSENGER's role in the ISON observation campaign. "The comet hasn't brightened as quickly as originally predicted, so we wondered how well we would do. Seeing it this early bodes well for our later observations."
A few days earlier, from November 6 through November 8, MESSENGER's imagers picked up its first snapshots of Encke. Unlike ISON, Encke has been known for quite a while. It was discovered in 1786 and recognized as a periodic comet in 1819. Its orbital period is 3.3 years -- the shortest period of any known comet -- and November 21 will mark its 62nd recorded perihelion.
"Encke has been on our radar for a long time because we've realized that it would be crossing MESSENGER's path in mid-November of this year," Vervack explained. "And not only crossing it, but coming very close to Mercury." These early images of both comets are little more than a few pixels across, Vervack said, but he expects improved images next week when the comets make their closest approaches to MESSENGER and Mercury.
On November 18, just a few days shy of its perihelion on November 21, Encke will travel within 2.3 million miles (3.7 million kilometers) of Mercury. According to the Minor Planet Center, if Encke came this close to Earth, it would rank as the third closest known approach of a comet to our planet. On November 19, ISON will pass within 22.5 million miles (36.2 million kilometers) of Mercury while at a distance of 44 million (71 million kilometers) from the Sun.
"By next week, we expect Encke to brighten by approximately a factor of 200 as seen from Mercury, and ISON by a factor of 15 or more," Vervack said. "So we have high hopes for better images and data." Three of MESSENGER's instruments -- MDIS, the Mercury Atmospheric and Surface Composition Spectrometer, and the X-Ray Spectrometer -- will be trained on the two comets and will collect as many observations as payload operational constraints will allow.
There are complicating issues that could impact the volume of data the team gathers, Vervack explained. "Closest approach occurs during what we call a 'hot season,'" he said. "So, for the health of the spacecraft, portions of each orbit must be spent in a thermally safe mode, which precludes gathering data over the entire orbit."
The critical observations also happen during a low-downlink period for MESSENGER. "We can't fill up the spacecraft recorder with comet data because doing so could cause a backlog that impacts our primary mission of collecting observations from Mercury," he said.
But the team is optimistic that all will go as planned, he said. "We just need the comets to hold up their end of the bargain."
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and entered orbit about Mercury on March 17, 2011 (March 18, 2011 UTC), to begin a yearlong study of its target planet. MESSENGER's first extended mission began on March 18, 2012, and ended one year later. MESSENGER is now in a second extended mission, which is scheduled to conclude in March 2015. Dr. Sean C. Solomon, the Director of Columbia University's Lamont-Doherty Earth Observatory, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
1,000th Featured Image from MESSENGER Posted on the Project's Web Gallery - September 10, 2013
The MESSENGER project is celebrating the posting today of the 1,000th featured image from Mercury. The Mercury Dual Imaging System (MDIS) team has posted a new image to the MESSENGER website approximately once per business day since March 29, 2011, when the first image obtained from orbit about the innermost planet was made public.
Today's image is a collage comprised entirely of earlier featured images. "I thought it sensible to produce a collage for the 1,000th web image because of the sheer volume of images the team has already posted, as no single picture could encompass the enormous breadth of Mercury science covered in these postings," explained MESSENGER Fellow Paul Byrne, of the Carnegie Institution of Washington. "Some of the images represent aspects of Mercury's geological characteristics, and others are fun extras, such as the U.S. Postal Service's Mercury stamp. The '1,000' superimposed on the collage is a reminder of the major milestone the team has reached in posting 1,000 featured images -- and even a motivation to post 1,000 more."
"During this two-year period, MESSENGER's daily web image has been a successful mechanism for sharing results from the mission with the public at large," said Nancy Chabot, MDIS Instrument Scientist at the Johns Hopkins University Applied Physics Laboratory (APL). Chabot has been leading the release of web images since MESSENGER's first flyby of Mercury, in January 2008.
"The first image I released was this one, as MESSENGER approached Mercury for the mission's first Mercury flyby," said Chabot. "Mercury was just a small crescent in the image, but it was still very exciting for me. We were obtaining the first spacecraft images of Mercury since Mariner 10 transmitted its final image in 1975, and this was just the beginning of the flood of images that followed."
Chabot said that over the subsequent five and a half years there have been other pivotal "image" moments, most notably the first image returned after the first Mercury flyby. "It was exciting to see a part of Mercury's surface that had never been seen at close range before," she said. "Much of the MESSENGER science team was gathered together in the project's Science Operations Center to see this first historic image, and it didn't disappoint anyone. I also found it rewarding to be able to share this image with the world so quickly afterwards by posting it on our website."
And then there was the first image acquired from Mercury orbit. "I was a bit of a nervous wreck waiting for the image to be downlinked to Earth," she said. "I had no rational reason to worry; but, then, sending the first spacecraft to orbit Mercury is difficult and challenging. When this beautiful image showed up, I was so happy, and I knew that it was just the first of many more to come."
The herculean effort involved in posting a new image every business day was made possible by a small team of scientists in addition to Chabot and Byrne, including APL's David Blewett, Brett Denevi, Carolyn Ernst, Rachel Klima, Nori Laslo, and Heather Meyer.
"Creating images and captions for the MESSENGER Image Gallery has been fun and interesting," Blewett said. "Working on a Gallery release gives me a chance take a break from my regular research and look all around Mercury's surface for an image that the general public might find to be engaging from a scientific, artistic, or humorous perspective (and sometimes all three!)."
"The posting of the 1,000th image of Mercury on our web gallery is a wonderful benchmark, but there's much more to come," adds MESSENGER Principal Investigator Sean Solomon of Columbia University's Lamont-Doherty Earth Observatory. "MESSENGER's altitude at closest approach is steadily decreasing, and in a little more than six months our spacecraft will be able to view Mercury at closer range than ever before with each orbit. Stay tuned!"
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and entered orbit about Mercury on March 17, 2011 (March 18, 2011 UTC), to begin a yearlong study of its target planet. MESSENGER's extended mission began on March 18, 2012, and ended one year later. A proposed second extended mission is currently under evaluation by NASA. Dr. Sean C. Solomon, the Director of Columbia University's Lamont-Doherty Earth Observatory, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
Planetary Data System Releases MESSENGER Data from Fourth Mercury Solar Day - September 6, 2013
Data collected during MESSENGER's 19th through 24th month in orbit around Mercury were released to the public today by the Planetary Data System (PDS), an organization that archives and distributes all of NASA's planetary mission data. With this release, data are now available to the public through the fourth full Mercury solar day of MESSENGER orbital operations.
This 10th delivery to PDS makes available the formatted raw and calibrated data for MESSENGER's science instruments and the radio science investigation. SPICE data from MESSENGER's 2004 launch through the period of this release are also included.
The availability of the new data comes on the heels of some highly anticipated upgrades to the MESSENGER mission's ACT-REACT-QuickMap software developed by Applied Coherent Technology Corporation. The software package allows users to examine global mosaics of Mercury constructed with high-resolution images from this and previous PDS deliveries. The Mercury Laser Altimeter (MLA) northern-hemisphere topographic map is now available at a higher resolution.
"Topography is important for understanding the volcanic and tectonic history of Mercury and, owing to fortunate geometry, the polar thermal environment and the emplacement of volatile ices as well," explains MLA Instrument Scientist Gregory Neumann, of the NASA Goddard Space Flight Center. "We have sharpened the picture of the north polar region considerably. The laser can corroborate the exciting results of the imaging campaign and see into the shadows. But we are still wrestling with the shape of Mercury, which is unusual among slowly rotating terrestrial bodies. These updates to the slowly accumulating topographic map will lead to further collaborations with other instrument teams and should reveal new surprises."
QuickMap now also provides a complete image mosaic, new elevation profiling and interactive three-dimensional viewing tools, and tools for viewing spectra from the Mercury Atmospheric and Surface Composition Spectrometer (MASCS) and the Mercury Dual Imaging System (MDIS).
"QuickMap's spectra retriever now allows users to find on the surface an individual footprint of the MASCS instrument," explains MASCS Instrument Scientist Noam Izenberg of the Johns Hopkins University Applied Physics Laboratory. "Each of these footprints varies in size and shape and contains an individual spectrum of the light reflected off the surface at wavelengths from 300 to 1,450 nanometers. The differences between these spectra from one place to another help to reveal differences in the composition of surface material on Mercury."
Brian Grigsby, the coordinator of MESSENGER's Student Planetary Investigator Program and science department chair at Shasta High School in Redding, California, says that the enhancements to QuickMap will allow students to gain a much deeper understanding of the surface morphology, geology, and planetary evolution of Mercury and to explore STEM-related career fields than they would not normally be able to do through conventional methods.
"The enhancements also can help the public acquire a broader view of surface features on Mercury from the topography data (to examine craters, hills, and valleys), and even 'colorized' views that can enhance certain features that aren't usually evident from grey-scale views of the surface," Grigsby says. "The new data will provide a much richer experience not only for students studying Mercury, but for the public as well."
QuickMap can be accessed via links on the MESSENGER websites at http://messenger.jhuapl.edu/ and http://www.nasa.gov/messenger. The MDIS mosaics can be downloaded from ../Explore/Images.html#global-mosaics/.
The data for this release are available online at http://pds.nasa.gov/subscription_service/SS-20130906.html, and all of the MESSENGER data archived at the PDS are available at http://pds.nasa.gov. The team will deliver the next mission data set to PDS in March 2014.
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and entered orbit about Mercury on March 17, 2011 (March 18, 2011 UTC), to begin a yearlong study of its target planet. MESSENGER's extended mission began on March 18, 2012, and ended one year later. A proposed second extended mission is currently under evaluation by NASA. Dr. Sean C. Solomon, the Director of Columbia University's Lamont-Doherty Earth Observatory, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
MESSENGER to Capture Images of Earth and Moon During Search for Satellites of Mercury - July 18, 2013
NASA's Mercury-orbiting MESSENGER spacecraft will capture images of Earth on July 19 and 20. The images will be taken at 7:49 a.m., 8:38 a.m. and 9:41 a.m. EDT on both days. Nearly half of the Earth, including all the Americas, Africa, and Europe, will be illuminated and facing MESSENGER, according to Hari Nair, the Johns Hopkins University Applied Physics Laboratory planetary scientist who designed and is implementing the campaign. The images on the second day will also include pictures of the Moon, where all six of the Apollo landing sites will be illuminated, 44 years to the day after Apollo 11 landed on the Moon's rocky surface.
"It's important to note that the Earth and Moon are going to be less than a pixel in size, and so no details will be seen," Nair cautioned. "In practice, all we're going to see are two bright dots."
These images of Earth and the Moon are coincidental, taken as part of a search for natural satellites around Mercury. Of all the planets, only Venus and Mercury have no known moons. Earth has one, and Mars has two. Jupiter and Saturn have dozens each; and even tiny Pluto is now known to have five moons.
Mercury's Moon Mystery
Scientists do not entirely understand how moons are formed, but there are several theories. Some of the moons around the giant planets probably formed from the disks of gas and dust that encircled those planets in the early solar system. Others, like Earth's Moon and Pluto's largest moon, Charon, were likely assembled from material ejected during collisions between the planet and a slightly smaller body. In still other cases, moons are thought to have originally been asteroids that passed sufficiently close to their host planet to be gravitationally captured.
"We don't know why Mercury does not have a moon," said William Merline, of the Southwest Research Institute (SwRI) in Boulder, Colorado, who, along with SwRI's Clark Chapman, leads MESSENGER's investigation of small bodies orbiting Mercury and in the inner solar system.
"It may have been just unfortunate in not having the right history, in terms of collisions," Merline continued. "Or it may at one time have had a moon in an orbital trajectory that was disrupted by the strong gravitational pull of the Sun, in combination with Mercury's highly eccentric (oblong) orbit around the Sun. Such an orbit makes the effect of the Sun's gravity highly variable with time, and may degrade the conditions for stability of a moon's orbit. But these possibilities are only speculations, based on theoretical ideas. To complete the picture, we must search for the existence of satellites to validate any of these suggestions."
During Mariner 10's first flyby of Mercury in 1974, its instruments detected an anomalous ultraviolet signal off the edge of Mercury's surface, leading a scientist to conclude that the signal was the result of a satellite. But the source of the signal was soon found to be a bright star with a high ultraviolet emission. Later, Mariner 10 performed a dedicated search for satellites and found none larger than 5 kilometers in diameter.
In February, MESSENGER, which began orbiting Mercury in March 2011, conducted its first search for satellites, and those data are still being studied. This search takes place during Mercury's aphelion, the planet's farthest point from the Sun. "This location has the advantage that the camera will be as cold as it ever gets," Nair explained. "Since we are looking for very faint objects, having a warm camera introduces thermal noise. The downside of being farther from the Sun is that any satellites will be dimmer at this time, as the Sun is their light source. So it was a tradeoff between brighter targets or a quieter detector, and we opted to go for a time when the detector would be quieter."
The team has also optimized the search pattern, taking many images at varying time intervals to spot faster-moving objects, according to Chapman. "The camera can potentially see objects as small as 100 meters, or 328 feet, in size, about the length of an American football field," he said.
MESSENGER's images of Earth and the Moon will be released next week. NASA's Cassini spacecraft, in orbit around Saturn, will also be acquiring images of Earth on July 19, between 5:27 and 5:42 p.m. EDT. The Cassini Earth portrait is part of a more extensive mosaic -- or multi-image picture -- of the Saturn system as it is backlit by the Sun.
"That images of our planet can be acquired on a single day from two distant outposts in the solar system provides a wonderful reminder of the vigor and excitement of this nation's ongoing program of planetary exploration," added MESSENGER Principal Investigator Sean Solomon, of Columbia University's Lamont-Doherty Earth Observatory. "The Saturn system and the innermost planet are two very different outcomes of planetary formation and evolution, so these two sets of images also prompt a sustained appreciation of the special attributes of Earth. There's no place like home."
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and entered orbit about Mercury on March 17, 2011 (March 18, 2011 UTC), to begin a yearlong study of its target planet. MESSENGER's extended mission began on March 18, 2012, and ended one year later. A proposed second extended mission is currently under evaluation by NASA. Dr. Sean C. Solomon, the Director of Columbia University's Lamont-Doherty Earth Observatory, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
The International Astronomical Union (IAU) -- the arbiter of planetary and satellite nomenclature since its inception in 1919 -- recently approved a proposal from the MESSENGER Science Team to assign names to 10 impact craters on Mercury. In keeping with the established naming theme for craters on Mercury, all of the newly designated features are named after famous deceased artists, musicians, or authors or other contributors to the humanities. The newly named craters are
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and entered orbit about Mercury on March 17, 2011 (March 18, 2011 UTC), to begin a yearlong study of its target planet. MESSENGER's extended mission began on March 18, 2012, and ended one year later. A proposed second extended mission is currently under evaluation by NASA. Dr. Sean C. Solomon, the Director of Columbia University's Lamont-Doherty Earth Observatory, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
IAU Approves New Names for Ten Major Fault Scarps on Mercury - June 7, 2013
The International Astronomical Union (IAU) recently approved a proposal from the MESSENGER Science Team to assign names to 10 rupes, the long cliff-like escarpments that formed over major faults along which one large block of crust on Mercury was thrust up and over another. The IAU has been the arbiter of planetary and satellite nomenclature since its inception in 1919. In keeping with the established naming theme for rupes on Mercury, all of the newly designated features are named after ships of discovery.
"We proposed the name Enterprise Rupes for the longest rupes on Mercury, which is 820 kilometers (510 miles) long. The USS Enterprise was launched in 1874 and conducted the first surveys of the Mississippi and Amazon rivers," says Michelle Selvans of the Center for Earth and Planetary Studies at the National Air and Space Museum. Selvans led the effort to name this group of rupes.
"We also recommended some fun names, such as Calypso Rupes, for Jacques Cousteau's ship," she says. And other names were proposed for their personal connections, such as Palmer Rupes, named after an icebreaker research vessel on which Selvans sailed to conduct marine geophysics research offshore of Antarctica. The other names are
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and entered orbit about Mercury on March 17, 2011 (March 18, 2011 UTC), to begin a yearlong study of its target planet. MESSENGER's extended mission began on March 18, 2012, and ended one year later. A possible second extended mission is currently under evaluation by NASA. Dr. Sean C. Solomon, the Director of Columbia University's Lamont-Doherty Earth Observatory, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
MESSENGER Completes Its 2,000th Orbit of Mercury, Provides Data on Solar Magnetic Field - May 24, 2013
MESSENGER began its 2,000th orbit around Mercury earlier this week, on May 22. The spacecraft completed its primary mission on March 17, 2012, and its first extended mission on March 17, 2013. The team is awaiting word from NASA on a proposal for a second extended mission. In the meantime, instruments aboard the spacecraft continue to gather new data on Mercury and its environment.
From May 6 to May 14, MESSENGER traversed a superior solar conjunction, during which the spacecraft was on the far side of the Sun from Earth. Scientists used the opportunity to measure the characteristics of the solar magnetic field from the Faraday rotation of its radio-frequency carrier.
"We found the orientation of the magnetic field within a coronal mass ejection (CME) that crossed the line of sight on May 10," says Elizabeth Jensen, of the Planetary Science Institute in Tucson, Arizona. "We saw the rotation of the plane of polarization of MESSENGER's radio-frequency signal as it moved deeper into the corona, giving information on the Sun's magnetic field configuration on May 11; and on May 12, we saw magnetohydrodynamic waves, a very important mode of energy transfer in the corona."
Solar storms cause communications disruptions, expose spacecraft and personnel in airplanes to radiation, and threaten electrical grids. Jensen says that the observations of the CME demonstrate the utility of this technique to predict the threat of solar storms headed toward Earth almost immediately after they erupt.
"Understanding the accuracy of models for the solar magnetic field and solar wind generation requires testing," she says. "Although other methods can be used in active regions, Faraday rotation is the only way to test the magnetic field models in the largest part of the corona where the solar wind is accelerating."
At its closest point to Mercury, MESSENGER will be about 447 kilometers (277.8 miles) above a point near 83.1° N latitude. Since its most recent orbit-correction maneuver on April 20, 2012, the spacecraft has completed three orbits of Mercury every day. At this rate, says mission trajectory lead James McAdams of the Johns Hopkins University Applied Physics Laboratory in Laurel, Maryland, the spacecraft will reach its 3,000th orbit around Mercury on April 20, 2014.
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and entered orbit about Mercury on March 17, 2011 (March 18, 2011 UTC), to begin a yearlong study of its target planet. MESSENGER's extended mission began on March 18, 2012, and ended one year later. A possible second extended mission is currently under evaluation by NASA. Dr. Sean C. Solomon, the Director of Columbia University's Lamont-Doherty Earth Observatory, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
The International Astronomical Union (IAU) — the arbiter of planetary and satellite nomenclature since its inception in 1919 — recently approved a proposal from the MESSENGER Science Team to assign names to nine impact craters on Mercury. In keeping with the established naming theme for craters on Mercury, all of the newly designated features are named after famous deceased artists, musicians, or authors or other contributors to the humanities. The newly named craters are
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and entered orbit about Mercury on March 17, 2011 (March 18, 2011 UTC), to begin a yearlong study of its target planet. MESSENGER's extended mission began on March 18, 2012, and ended one year later. A possible second extended mission is currently under evaluation by NASA. Dr. Sean C. Solomon, the Director of Columbia University's Lamont-Doherty Earth Observatory, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
MESSENGER Completes Its First Extended Mission at Mercury - March 18, 2013
On March 17, 2013, MESSENGER successfully completed its year-long first extended mission in orbit about Mercury, building on the groundbreaking scientific results from its earlier primary mission. Today the team is poised to embark on a second extended mission that promises to provide new observations of Mercury's surface and interior at unprecedented spatial resolution and of the planet's dynamic magnetosphere and exosphere at high time resolution during the peak and declining phase of the current solar cycle.
"NASA is currently considering a second extension to mission operations and until the formal decision is made has asked that we continue to operate the spacecraft and its scientific instruments," says MESSENGER Project Manager Helene Winters of the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Maryland.
During its first extended mission, MESSENGER completed 12 specialized measurement campaigns that led to new discoveries about surface volatiles on Mercury, the duration of volcanism, the evolution of long-wavelength topography, the nature of localized regions of enhanced exospheric density, the effect of the solar cycle on Mercury's exosphere, and Mercury's energetic electrons.
Among the most recent results was confirmation of the long-held theory that the planet harbors abundant water ice and other frozen volatile materials within its permanently shadowed polar craters.
If approved by NASA, a second extended mission would seek answers to still further questions, each stimulated by findings from the primary mission and first extended mission, including:
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and entered orbit about Mercury on March 17, 2011 (March 18, 2011 UTC), to begin a yearlong study of its target planet. MESSENGER's extended mission began on March 18, 2012, and ended one year later. A possible second extended mission is currently under evaluation by NASA. Dr. Sean C. Solomon, the Director of Columbia University's Lamont-Doherty Earth Observatory, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
The Planetary Data System (PDS), which archives and distributes data from all of NASA's planetary missions, today released data collected during MESSENGER's thirteenth through eighteenth month in orbit around Mercury. With this release, images and measurements are now available to the public for the third full Mercury solar day of MESSENGER orbital operations.
NASA requires that all of its planetary missions archive data in the PDS, which makes available well-documented, peer-reviewed data to the research community. This ninth delivery of MESSENGER measurements includes raw and calibrated data from all seven of the mission's science instruments, plus radio science data from the spacecraft telecommunications system, from March 25 to September 17, 2012.
The team has also provided, for the first time in this release, advanced products created with data collected through March 25, 2012, encompassing the first two full Mercury solar days of MESSENGER orbital operations. Those products include the first global mosaics of Mercury to be delivered to PDS.
"The two advanced image products in this release are an eight-color map and a higher-resolution monochrome map," says Mercury Dual Imaging System (MDIS) Instrument Scientist Nancy Chabot, of the Johns Hopkins University Applied Physics Laboratory (APL). "They are both the products of thousands of images mosaicked together to reveal Mercury's global geology and color characteristics. These mosaics required considerable effort by many on the MESSENGER team, and we are all very proud to make these global maps available."
Other advanced products include summed gamma-ray spectra and background-subtracted, geolocated neutron counts from the Gamma-Ray and Neutron Spectrometer; time-averaged magnetic field data from the Magnetometer; altimeter profiles, radiometry, and a northern hemisphere digital elevation map produced with data from the Mercury Laser Altimeter (MLA); limb tangent height and surface reflectance spectra from the Mercury Atmospheric and Surface Composition Spectrometer; pitch-angle and measured-flux distributions and energy spectra from the Energetic Particle and Plasma Spectrometer; and occultation data and spherical harmonic gravity and shape models derived from the radio science investigation and the MLA.
"Many in the public have been eagerly awaiting the release of the MESSENGER advanced products, and the MESSENGER team is excited to be able to provide them," says APL's Susan Ensor, MESSENGER's Science Operations Center lead. "Extra analyses and processing are required to generate these products, which in many cases combine data over time and include maps, topography, and other global data. The team has also worked closely with the PDS in planning and documenting these new products to ensure their long-term usefulness to the science community."
"Mercury is a planet of many mysteries," adds MESSENGER Principal Investigator Sean Solomon, of Columbia University's Lamont-Doherty Earth Observatory. "With each increment of data, we have made discoveries that raised new questions. Finding answers to those questions requires further analysis. We hope that this latest release of MESSENGER data will induce more of our colleagues from the broader planetary science community to help us unravel the many stories that Mercury has yet to tell."
The MESSENGER mission's ACT-REACT-QuickMap software, developed by Applied Coherent Technology Corporation, allows users to examine global mosaics constructed with high-resolution images from this and previous PDS deliveries. The tool also provides weekly updates of coverage for surface-observing instruments, as well as the status of specially targeted MDIS observations. Future enhancements to QuickMap will include simple data fusion, by which data sets from multiple elements of the payload may be combined.
QuickMap can be accessed via links on the MESSENGER websites at http://messenger.jhuapl.edu/ and http://www.nasa.gov/messenger. The MDIS mosaics can be downloaded from ../Explore/Images.html#global-mosaics.
The data for this release are available online at http://pds.nasa.gov/subscription_service/SS-20130308.html, and all of the MESSENGER data archived at the PDS thus far are available at http://pds.nasa.gov. The team will submit two more data deliveries to PDS at six-month intervals from MESSENGER's extended mission.
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and entered orbit about Mercury on March 17, 2011 (March 18, 2011 UTC), to begin a yearlong study of its target planet. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
MESSENGER's Discoveries Tapped as among Top Space Stories of 2012 - January 4, 2013
In 2012, the MESSENGER mission to Mercury completed its primary mission, embarked on an extended mission, saw its images and maps featured on a highly rated television show, sponsored the release of a dedicated app, and celebrated the 8th anniversary of its launch, all the while continuing to produce new findings about the planet closest to the Sun.
These accomplishments captured the attention of many media outlets, several of which designated MESSENGER's endeavors as a "top story" of 2012.
"In late November, scientists discovered water on a planet beginning with the letter M — just not the one we were expecting," wrote Eric Olson of Scientific American, which listed MESSENGER as one of the top 5 space stories of 2012. "As the data keeps pouring in we can probably expect more news on Mercury in 2013," he predicted.
MESSENGER's confirmation of ice at Mercury's poles also prompted editors at The Huffington Post to include the mission in its Year in Science: Inspiring Discoveries & Important Events.
The International Business Times — referring to the spacecraft as "plucky" — deemed MESSENGER's confirmation of ice on Mercury one of the biggest space stories of 2012.
NASA SpaceFlight.com offered a yearlong review of MESSENGER's accomplishments, declaring that it "offered one of the most exciting missions of the 2012 year."
"We learned a great deal about Mercury over the past year," adds MESSENGER Principal Investigator Sean Solomon, of Columbia University's Lamont-Doherty Earth Observatory. "The team published three dozen scientific and technical papers and delivered more than 150 presentations at national and international meetings. New measurements continue to stream back from our spacecraft, and we can look forward with excitement to many additional discoveries in 2013."
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and entered orbit about Mercury on March 17, 2011 (March 18, 2011 UTC), to begin a yearlong study of its target planet. MESSENGER's extended mission began on March 18, 2012. Dr. Sean C. Solomon, the director of Columbia University's Lamont-Doherty Earth Observatory, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
Recently Named Mercury Craters Honor Blues Singer and Animation Pioneer - December 21, 2012
The International Astronomical Union (IAU) recently approved a proposal from the MESSENGER Science Team to assign names to nine impact craters on Mercury. The IAU has been the arbiter of planetary and satellite nomenclature since its inception in 1919. In keeping with the established naming theme for craters on Mercury, all of the newly designated features are named after famous deceased artists, musicians, or authors or other contributors to the humanities. The newly named craters are:
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and entered orbit about Mercury on March 17, 2011 (March 18, 2011 UTC), to begin a yearlong study of its target planet. MESSENGER's extended mission began on March 18, 2012. Dr. Sean C. Solomon, the director of Columbia University's Lamont-Doherty Earth Observatory, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
MESSENGER Finds New Evidence for Water Ice at Mercury's Poles - November 29, 2012
New observations by the MESSENGER spacecraft provide compelling support for the long-held hypothesis that Mercury harbors abundant water ice and other frozen volatile materials in its permanently shadowed polar craters.
Three independent lines of evidence support this conclusion: the first measurements of excess hydrogen at Mercury's north pole with MESSENGER's Neutron Spectrometer, the first measurements of the reflectance of Mercury's polar deposits at near-infrared wavelengths with the Mercury Laser Altimeter (MLA), and the first detailed models of the surface and near-surface temperatures of Mercury's north polar regions that utilize the actual topography of Mercury's surface measured by MLA. These findings are presented in three papers published online today in Science Express.
Given its proximity to the Sun, Mercury would seem to be an unlikely place to find ice. But the tilt of Mercury's rotational axis is almost zero -- less than one degree -- so there are pockets at the planet's poles that never see sunlight. Scientists suggested decades ago that there might be water ice and other frozen volatiles trapped at Mercury's poles.
The idea received a boost in 1991, when the Arecibo radio telescope in Puerto Rico detected unusually radar-bright patches at Mercury's poles, spots that reflected radio waves in the way one would expect if there were water ice. Many of these patches corresponded to the location of large impact craters mapped by the Mariner 10 spacecraft in the 1970s. But because Mariner saw less than 50 percent of the planet, planetary scientists lacked a complete diagram of the poles to compare with the images.
MESSENGER's arrival at Mercury last year changed that. Images from the spacecraft's Mercury Dual Imaging System taken in 2011 and earlier this year confirmed that radar-bright features at Mercury's north and south poles are within shadowed regions on Mercury's surface, findings that are consistent with the water-ice hypothesis.
Now the newest data from MESSENGER strongly indicate that water ice is the major constituent of Mercury's north polar deposits, that ice is exposed at the surface in the coldest of those deposits, but that the ice is buried beneath an unusually dark material across most of the deposits, areas where temperatures are a bit too warm for ice to be stable at the surface itself.
MESSENGER uses neutron spectroscopy to measure average hydrogen concentrations within Mercury's radar-bright regions. Water ice concentrations are derived from the hydrogen measurements. "The neutron data indicate that Mercury's radar-bright polar deposits contain, on average, a hydrogen-rich layer more than tens of centimeters thick beneath a surficial layer 10 to 20 centimeters thick that is less rich in hydrogen," writes David Lawrence, a MESSENGER Participating Scientist based at the Johns Hopkins University Applied Physics Laboratory and the lead author of one of the papers. "The buried layer has a hydrogen content consistent with nearly pure water ice."
Data from MESSENGER's Mercury Laser Altimeter (MLA) -- which has fired more than 10 million laser pulses at Mercury to make detailed maps of the planet's topography -- corroborate the radar results and Neutron Spectrometer measurements of Mercury's polar region, writes Gregory Neumann of the NASA Goddard Flight Center. In a second paper, Neumann and his colleagues report that the first MLA measurements of the shadowed north polar regions reveal irregular dark and bright deposits at near-infrared wavelength near Mercury's north pole.
"These reflectance anomalies are concentrated on poleward-facing slopes and are spatially collocated with areas of high radar backscatter postulated to be the result of near-surface water ice," Neumann writes. "Correlation of observed reflectance with modeled temperatures indicates that the optically bright regions are consistent with surface water ice."
The MLA also recorded dark patches with diminished reflectance, consistent with the theory that the ice in those areas is covered by a thermally insulating layer. Neumann suggests that impacts of comets or volatile-rich asteroids could have provided both the dark and bright deposits, a finding corroborated in a third paper led by David Paige of the University of California, Los Angeles.
Paige and his colleagues provided the first detailed models of the surface and near-surface temperatures of Mercury's north polar regions that utilize the actual topography of Mercury's surface measured by MLA. The measurements "show that the spatial distribution of regions of high radar backscatter is well matched by the predicted distribution of thermally stable water ice," he writes.
According to Paige, the dark material is likely a mix of complex organic compounds delivered to Mercury by the impacts of comets and volatile-rich asteroids, the same objects that likely delivered water to the innermost planet. The organic material may have been darkened further by exposure to the harsh radiation at Mercury's surface, even in permanently shadowed areas.
This dark insulating material is a new wrinkle to the story, says Sean Solomon of the Columbia University's Lamont-Doherty Earth Observatory, principal investigator of the MESSENGER mission. "For more than 20 years the jury has been deliberating on whether the planet closest to the Sun hosts abundant water ice in its permanently shadowed polar regions. MESSENGER has now supplied a unanimous affirmative verdict."
"But the new observations have also raised new questions," adds Solomon. "Do the dark materials in the polar deposits consist mostly of organic compounds? What kind of chemical reactions has that material experienced? Are there any regions on or within Mercury that might have both liquid water and organic compounds? Only with the continued exploration of Mercury can we hope to make progress on these new questions."
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and entered orbit about Mercury on March 17, 2011 (March 18, 2011 UTC), to begin a yearlong study of its target planet. MESSENGER's extended mission began on March 18, 2012. Dr. Sean C. Solomon, the director of Columbia University's Lamont-Doherty Earth Observatory, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
NASA Hosts Nov. 29 News Conference about Mercury Polar Regions - November 26, 2012
Dwayne Brown
Headquarters, Washington
202-358-1726
dwayne.c.brown@nasa.gov
Paulette Campbell
Johns Hopkins University Applied Physics Laboratory, Laurel, Md.
240-228-6792
paulette.campbell@jhuapl.edu
MEDIA ADVISORY: M12-219
NASA HOSTS NOV. 29 NEWS CONFERENCE ABOUT MERCURY POLAR REGIONS
WASHINGTON -- NASA will host a news conference at 2 p.m. EST on Thursday, Nov, 29, to reveal new observations from the first spacecraft to orbit the planet Mercury. The briefing will be held in the NASA Headquarters auditorium, located at 300 E St. SW in Washington.
Science Journal has embargoed details until 2 p.m. on Nov. 29. The news conference will be carried live on NASA Television and the agency's website.
NASA's Mercury Surface, Space Environment, Geochemistry, and Ranging, or MESSENGER spacecraft has been studying Mercury in unprecedented detail since its historic arrival there in March 2011.
The news conference participants are:
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and entered orbit about Mercury on March 17, 2011 (March 18, 2011 UTC), to begin a yearlong study of its target planet. MESSENGER's extended mission began on March 18, 2012. Dr. Sean C. Solomon, the director of Columbia University's Lamont-Doherty Earth Observatory, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
MESSENGER Finds Unusual Groups of Ridges and Troughs on Mercury - November 15, 2012
MESSENGER has discovered assemblages of tectonic landforms unlike any previously found on Mercury or elsewhere in the Solar System. The findings are reported in a paper led by Smithsonian scientist Thomas Watters, "Extension and contraction within volcanically buried impact craters and basins on Mercury," published in the December issue of the journal Geology.
The surface of Mercury is covered with deformational landforms that formed by faulting in response to horizontal contraction or shortening as the planet's interior cooled and surface area shrank, causing blocks of crustal material to be pushed together. Contraction from cooling of Mercury's interior has been so dominant that extensional landforms caused by fault formation in response to horizontal stretching and pulling apart of crustal material had not been previously documented outside of the interiors of a few large impact basins.
The MESSENGER spacecraft, in orbit around Mercury since March of last year, has revealed families of extensional troughs, or graben, that are encircled by contractional wrinkle ridges arranged in circular rings. The troughs can form complex patterns varying from the outlines of polygons inside the ridge rings to arcs that parallel the bounding ridges.
"The pattern of winkle ridges and graben resembles the raised edge and cracks in a pie crust," said Watters of the Center for Earth and Planetary Studies at the National Air and Space Museum. The "pie crust" analogy also fits another notable aspect of these collections of tectonic landforms -- their association with "ghost" craters. Ghost craters are impact craters that have been flooded and buried by lava flows. The thin volcanic deposits overlying the rim of a fully buried impact crater serve to concentrate contractional forces, leading to the formation of a ridge ring that reveals the outline of the buried crater.
"The special arrangement of the wrinkle ridges and graben in many of the ghost craters on Mercury is due to a combination of extensional forces from cooling and contraction of unusually thick lava flow units and contractional forces from cooling and contraction of the planet's interior," says Sean Solomon of the Columbia University's Lamont-Doherty Earth Observatory, coauthor and principal investigator of the MESSENGER mission. The eruption and rapid accumulation of very fluid lava flows into thick cooling units on a planet undergoing a high rate of global contraction may be why these systems of tectonic landforms in ghost craters on Mercury have not been seen elsewhere in the Solar System.
The article is available online at http://geology.gsapubs.org/content/40/12/1123.full.
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and entered orbit about Mercury on March 17, 2011 (March 18, 2011 UTC), to begin a yearlong study of its target planet. MESSENGER's extended mission began on March 18, 2012. Dr. Sean C. Solomon, the director of Columbia University's Lamont-Doherty Earth Observatory, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
MESSENGER Mission Receives the IAA Laurels for Team Achievement Award - October 4, 2012
The International Academy of Astronautics (IAA) has awarded the 2012 Laurels for Team Achievement Award to the MESSENGER team. The award was presented September 30 at the opening ceremony of the 63rd International Astronautical Congress, which is being held this week in Naples.
MESSENGER Project Scientist Ralph McNutt, MESSENGER Co-investigator Stamatios Krimigis, and MESSENGER Mission Design Lead Engineer James McAdams were on hand to accept the award before an audience of 300, including 14 heads of space agencies. In introductory remarks, Yannick d'Escatha, director of the French Space Agency, vice president of IAA and chair of the awards committee, called the MESSENGER mission a "fantastic and extraordinary accomplishment."
The citation for MESSENGER's award reads: "To the team of scientists and engineers whose creativity and expertise made possible the development and operation of the MESSENGER Mission, the first to orbit Mercury, as a breakthrough in scientific solar system exploration. During its unprecedented one-year primary mission, this robotic explorer has provided an extraordinary, comprehensive scientific overview of the planet, its makeup, its exosphere and its magnetosphere, providing the text for a new and overdue chapter of humankind's knowledge of the smallest of the terrestrial planets. This unique achievement of technology was conducted by the JHU APL and accomplished with the collaboration of NASA."
John Sommerer, the head of the Space Department at the Johns Hopkins University Applied Physics Laboratory (APL), which built and operates the spacecraft, said: "APL is very pleased with this international recognition. To have accomplished such a complete characterization of this little-known planet, within the low-cost Discovery mission class, is a testament to the vision and skill of the science, engineering, and operations team responsible for MESSENGER."
The Laurels Team Achievement Award is one of the two major awards given by IAA every year, the other for individual recipients. The team award was established in 2001 to recognize extraordinary performance and achievement by a team of scientists, engineers, and managers in the field of astronautics. Past recipients of the award have gone to the teams of the Cassini-Huygens Program (2006), the Hubble Space Telescope (2004) and the U.S. Space Shuttle (2002).
"This is a special honor for MESSENGER, when one knows that previous winners include Hubble, Cassini, SOHO, and the U.S. Space Shuttle Team, among others," said Krimigis of APL. "We are in select company, indeed."
"From the outset of this mission, MESSENGER has been a team effort. Our scientists, engineers, managers, and operations staff have worked in close cooperation for more than 12 years to maximize the effectiveness and impact of this hardy and well-traveled spacecraft," says MESSENGER Principal Investigator Sean Solomon of Columbia University's Lamont-Doherty Earth Observatory. "It is appropriate that this honor be shared across the entire mission team, and all team members share my gratitude that the International Academy of Astronautics has seen fit to acknowledge the accomplishments of the MESSENGER mission with this wonderful award."
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and entered orbit about Mercury on March 17, 2011 (March 18, 2011 UTC), to begin a yearlong study of its target planet. MESSENGER's extended mission began on March 18, 2012. Dr. Sean C. Solomon, the director of Columbia University's Lamont-Doherty Earth Observatory, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
MESSENGER's X-Ray Spectrometer Reveals Chemical Diversity on Mercury's Surface - September 21, 2012
New data from the X-Ray Spectrometer (XRS) on the MESSENGER spacecraft -- one of two instruments designed to measure the abundances of many key elements on Mercury -- show variations in the composition of surface material on Mercury that point to changes over time in the characteristics of volcanic eruptions on the solar system's innermost planet.
In results to be published in the Journal of Geophysical Research, scientists report that Mercury's volcanic smooth plains units differ in composition from older surrounding terrains. The older terrain has higher ratios of magnesium to silicon, sulfur to silicon, and calcium to silicon, but lower ratios of aluminum to silicon, suggesting that the smooth plains material erupted from a magma source that was chemically different from the source of the material in the older regions, explains Shoshana Weider of the Carnegie Institution of Washington, the lead author on the paper.
"The new findings further illuminate the geological history of the planet," she says. "We now know that these areas are compositionally distinct, indicating that different parts of Mercury's mantle melted at different times and temperatures, and through volcanic activity created the materials in the different terrains."
Weider and her co-authors also report that Mercury's surface is dominated by minerals high in magnesium and enriched in sulfur.
"None of the other terrestrial planets have such high levels of sulfur. We are seeing about ten times the amount of sulfur than on Earth and Mars," Weider says. "In terms of magnesium, we do have some materials on Earth that are high in magnesium. They tend to be ancient volcanic rocks that formed from very hot lavas. So this composition on Mercury tells us that eruptions of high-temperature lavas might have formed these high-magnesium materials."
These findings stem from the team's analysis of 205 X-ray measurements of Mercury's surface, focusing on the large expanse of smooth volcanic plains at high northern latitudes and surrounding areas that are higher in crater density and therefore older than the northern plains. Weider says the measurements support what other MESSENGER scientists have observed from the mission's images. "Now we can correlate their findings with our data, providing increased confidence in what we are discovering about the planet," she says.
MESSENGER has been orbiting Mercury since March 2011, and has been revealing new information about the surface chemistry and geological history of the innermost planet in the solar system. The XRS measures elemental abundances on the surface of Mercury by detecting fluorescent X-ray emissions induced on the planet's surface by the incident solar X-ray flux. The instrument began orbital observations on March 23, 2011, and has observed X-ray fluorescence from the surface of the planet whenever a sunlit portion of Mercury has been within the XRS field of view.
"The X-ray spectrometer focuses on the estimation of elemental abundances on Mercury; i.e., the amount of magnesium, aluminum, sulfur, calcium, and iron in surface material," Weider says. "From there we can start to work out what kinds of minerals are present, then the types of rocks that were formed, and then we can start to unravel the geological history."
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and entered orbit about Mercury on March 17, 2011 (March 18, 2011 UTC), to begin a yearlong study of its target planet. MESSENGER's extended mission began on March 18, 2012. Dr. Sean C. Solomon, the director of Columbia University's Lamont-Doherty Earth Observatory, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
MESSENGER Data from Second Full Mercury Solar Day in Orbit Released by Planetary Data System - September 11, 2012
Late last week, the Planetary Data System (PDS) released data collected during MESSENGER's seventh through twelfth month in orbit around Mercury. PDS archives and distributes all of NASA's planetary mission data. With this release, images and measurements are now available to the public for the second full Mercury solar day of MESSENGER orbital operations.
NASA requires that all of its planetary missions archive data in the PDS, an active archive that makes available well-documented, peer-reviewed data to the research community. The PDS includes eight science teams, called discipline nodes, each of which is centered at a university or research institution and specializes in a specific area of planetary data. The contributions from these nodes provide a data-rich source for scientists, researchers, and developers.
In this eighth release of MESSENGER measurements by PDS, calibrated data from all seven of the mission's science instruments, plus radio science data from the spacecraft telecommunications system, are included. The MESSENGER team has created a software tool with which the public can view data from this delivery. ACT-REACT-QuickMap provides an interactive Web interface to MESSENGER data. Developed by Applied Coherent Technology Corporation, the software allows users to examine global mosaics constructed with high-resolution images from this and previous PDS deliveries.
The tool also provides weekly updates of coverage for surface-observing instruments, as well as the status of specially targeted MDIS observations. Information is also available that can be used to locate MESSENGER data products at the PDS. QuickMap can be accessed via links on the MESSENGER websites at http://messenger.jhuapl.edu/ and http://www.nasa.gov/messenger. The MDIS mosaics can be downloaded from ../Explore/Images.html#global-mosaics.
All of the MESSENGER data archived at the PDS thus far are available at http://pds.nasa.gov. The team will submit three more data deliveries to PDS at six-month intervals from MESSENGER's primary orbital mission and its extended mission.
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and entered orbit about Mercury on March 17, 2011 (March 18, 2011 UTC), to begin a yearlong study of its target planet. MESSENGER's extended mission began on March 18, 2012. Dr. Sean C. Solomon, the director of Columbia University's Lamont-Doherty Earth Observatory, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
MESSENGER Team Mourns the Loss of Neil Armstrong - August 27, 2012
The news of Neil Armstrong's death this weekend left many members of the MESSENGER team mourning his loss and reflecting on his legacy. Armstrong died on August 25, at the age of 82. He commanded the Apollo 11 spacecraft that landed on the Moon on July 20, 1969; and an estimated 600 million people witnessed, by television or radio, as he became the first man to set foot on its surface.
"Neil Armstrong was an enduring icon for all of us interested in space and planetary exploration," says MESSENGER Principal Investigator Sean Solomon of Columbia University's Lamont-Doherty Earth Observatory. "The Apollo 11 landing and Armstrong's first footstep on another world linked, in one historic instant, all of humanity with access to television or radio. That Armstrong's passing was barely one month after that of Sally Ride reminds us that the first pioneers of space travel transcended gender but were united by a courageous sense of adventure and wonder."
Larry Nittler, MESSENGER's Deputy Principal Investigator and a cosmochemist in the Department of Terrestrial Magnetism of the Carnegie Institution of Washington, adds, "Although I was only an infant when Neil Armstrong walked on the Moon, some of my earliest memories are of returning Apollo capsules. The extraordinary achievements of Armstrong and the other Apollo astronauts had an enormous impact on my life, certainly influencing my decision to go into planetary science."
Although Armstrong is best known for the historic moonwalk, that feat topped a string of accomplishments that included piloting the X-15 rocket plane and completing the first space docking maneuver during the Gemini 8 mission, which included a successful emergency landing. In the early 1960s, the X-15 became the first winged aircraft to attain hypersonic velocities of Mach 4, 5, and 6 (four to six times the speed of sound) and to operate at altitudes well above 100,000 feet.
"X-15 flew to the edge of space 199 times, and Armstrong made seven of those flights," notes APL's MESSENGER Project Scientist Ralph McNutt, of the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Maryland. "I also remember well his salvage of the Gemini 8 mission -- a key to the lunar orbit rendezvous approach to manned lunar landings -- and his last-minute escape from the 'flying bedstead' (a nickname given to two experimental aircraft) during the development of Apollo, when America's race to the Moon with the Soviets had real, and serious, implications for the winner."
For teenagers across the country, McNutt says, Armstrong brought to life the iconic and heroic character typical in science-fiction books -- "the engineer/pilot, the astronaut who was leading American technology forward and humanity to the skies and beyond" -- inspiring legions to become space explorers.
MESSENGER Science Payload Manager Robert Gold of APL, agrees. "Armstrong's first step on the Moon confirmed my resolve to understand how our solar system works and how the Sun affects our life on Earth."
Brown University's James Head, a MESSENGER Co-Investigator, called Armstrong "a wonderful example of the type of selfless dedication that can enable this country to accomplish things that seem impossible." Head's first job after graduate school was with the Apollo Lunar Exploration Program.
"All of the Apollo astronauts were experienced, intelligent, highly motivated, and fully dedicated to President Kennedy's goal of landing a human on the Moon and returning them safely by the end of the decade," says Head. "Neil Armstrong stood out to me because of his complete dedication and professionalism, his unflappable nature, and his immediate personal acceptance of anyone who had something to say that would help accomplish the President's goal, even a young twenty-something who was excited about the geology of the Moon."
MESSENGER Co-Investigator Stamatios M. Krimigis, of APL, remembers talking with Armstrong at length in the late 1980s during the time of his testimony to the Augustine Commission (of which Armstrong was a member) on the future of the U.S. space program. "In that discussion I found him to be a thoughtful and modest person ... and fully appreciative of the key role of robotic spacecraft in space exploration," Krimigis says. "Thinking back on that conversation, I can fully appreciate his family's description of him as a 'reluctant American hero.' His modesty and humility are a lesson for us all."
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and entered orbit about Mercury on March 17, 2011 (March 18, 2011 UTC), to begin a yearlong study of its target planet. MESSENGER's extended mission began on March 18, 2012. Dr. Sean C. Solomon, the director of Columbia University's Lamont-Doherty Earth Observatory, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
The International Astronomical Union (IAU) recently approved a proposal from the MESSENGER Science Team to assign names to nine impact craters on Mercury. The IAU has been the arbiter of planetary and satellite nomenclature since its inception in 1919. In keeping with the established naming theme for craters on Mercury, all of the newly designated features are named after famous deceased artists, musicians, or authors or other contributors to the humanities.
"All of the nine newly named craters are located in Mercury's north polar region, and MESSENGER team members and collaborators who are researching this area contributed the proposed names," explains Mercury Dual Imaging System Instrument Scientist Nancy Chabot, of the Johns Hopkins University Applied Physics Laboratory in Laurel, Maryland. "Mercury's north polar region is of high scientific interest because of the shadowed craters there that host radar-bright deposits that may consist of water ice. All of the nine newly named craters host such deposits."
The newly named craters are:
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and entered orbit about Mercury on March 17, 2011 (March 18, 2011 UTC), to begin a yearlong study of its target planet. MESSENGER's extended mission began on March 18, 2012. Dr. Sean C. Solomon, the director of Columbia University's Lamont-Doherty Earth Observatory, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
MESSENGER Marks 8th Anniversary of Launch - August 3, 2012
The MESSENGER spacecraft launched eight years ago today — on August 3, 2004 — embarking on a six-and-a-half year journey to become the first spacecraft to orbit Mercury. The spacecraft's 4.9-billion mile (7.9-billion kilometer) cruise to history included 15 trips around the Sun, a flyby of Earth, two flybys of Venus, and three flybys of Mercury.
The mission began capturing ground-breaking science and images from outer space almost immediately. During its gravity assist swing-by of Earth, on August 2, 2005, MESSENGER's cameras captured several hundred images of our planet. These images were sequenced into a movie documenting the view from MESSENGER as it departed Earth toward the inner Solar System.
On October 24, 2006, the spacecraft soared above the cloud deck of Venus for the first time, then returned less than a year later on June 5, 2007, marking the first time in flight that all seven instruments were turned on and operating collectively in science-observing mode. MESSENGER turned its wide-angle camera back to the planet and acquired a departure sequence that provided a spectacular good-bye to the cloud-shrouded planet while also acquiring valuable calibration data for the camera team.
MESSENGER made history on January 14, 2008, when it flew over a portion of Mercury that had never before been seen at close range. In this first of three flybys of the planet, the probe's cameras took 1,213 images and other sophisticated instruments made the first spacecraft measurements of the planet and its environment since Mariner 10's third and final flyby on March 16, 1975.
The mission's penultimate accomplishment — entering orbit about Mercury — was celebrated on March 17, 2011, by a crowd of hundreds gathered at the Johns Hopkins University Applied Physics Laboratory in Laurel, Maryland. The event was covered live, and the webcast is still available online here.
On March 17, 2012, MESSENGER successfully completed a year-long campaign to perform the first global reconnaissance of the geochemistry, geophysics, geologic history, atmosphere, magnetosphere, and plasma environment of the solar system's innermost planet. The following day, March 18, 2012, marked the official start of an extended mission phase designed to build upon those discoveries. This animation shows a sunward view of MESSENGER above Mercury's north polar region during the two orbit-correction maneuvers on April 16 and April 20, 2012, which shortened the orbit period from 12 to 8 hours, allowing MESSENGER an even closer look at the planet.
Less than five months into the extended mission, the team has already made substantial progress on its new objectives. Next week, the team will gather for its 27th Science Team Meeting in Salem, Massachusetts, to discuss the new findings and firm up plans for a second extended mission.
"Our small spacecraft has been a hardy traveler," says MESSENGER Principal Investigator Sean Solomon, of the Lamont-Doherty Earth Observatory at Columbia University. "Across billions of miles, during more than 1,000 orbits about the planet with the greatest extremes in surface temperature, and in the face of streams of energetic particles from an increasingly active Sun, MESSENGER has continued to surpass expectations. Mercury, too, has continued to surprise the scientific community, and the MESSENGER team looks forward to learning more about one of the nearest yet least studied worlds."
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and entered orbit about Mercury on March 17, 2011 (March 18, 2011 UTC), to begin a yearlong study of its target planet. MESSENGER's extended mission began on March 18, 2012. Dr. Sean C. Solomon, the director of Columbia University's Lamont-Doherty Earth Observatory, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
MESSENGER Completes Its 1,000th Orbit of Mercury - June 22, 2012
MESSENGER will complete its 1,000th orbit of the planet closest to the Sun at 11:22 p.m. EDT tonight. "Reaching this milestone is yet another testimony to the hard work and dedication of the full MESSENGER team that has designed, launched, and operated this highly successful spacecraft," says the mission trajectory lead Jim McAdams of the Johns Hopkins University Applied Physics Laboratory in Laurel, Md.
The spacecraft was inserted into orbit around Mercury in mid-March 2011, after travelling more than 15 times around the Sun through the inner solar system and completing six planetary flybys. "Since arriving at Mercury, MESSENGER took a little more than 15 months to reach this mark," McAdams notes. "But because the orbital period has been reduced from just under 12 hours to 8 hours, it will take only 11 months to complete the next 1,000 orbits."
During its primary mission, which concluded on March 17, 2012, MESSENGER performed the first global reconnaissance of the geochemistry, geophysics, geologic history, atmosphere, magnetosphere, and plasma environment of Mercury. The spacecraft is now more than one-quarter of the way into a one-year extended mission that is building on this knowledge to address new questions raised by the initial orbital observations.
"Mercury is in a tough neighborhood, with high temperatures and increasingly frequent streams of solar energetic particles," says MESSENGER Principal Investigator Sean Solomon, of the Carnegie Institution of Washington. "It is therefore all the more remarkable that this spacecraft has met the challenge to perform as designed after 1,000 orbits about the innermost planet in our solar system. There is much more science ahead for this mission."
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and entered orbit about Mercury on March 17, 2011 (March 18, 2011 UTC), to begin a yearlong study of its target planet. MESSENGER's extended mission began on March 18, 2012. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
MESSENGER scientists have concluded that waves driven by the Kelvin-Helmholtz (KH) instability play a key role in driving Mercury's magnetosphere. In a paper published recently in the Journal of Geophysical Research, the team reports on frequent detections of such waves at the outer edge of the innermost planet's magnetosphere.
The paper was selected as an Editor's Highlight by the journal editor, and its findings are scheduled to be featured as a Research Highlight in Eos, the weekly newspaper of the American Geophysical Union.
KH waves can develop at boundaries between two media in relative motion. "In principle, they are similar to the surface waves on water when there's a strong wind blowing," explains Torbjorn Sundberg, a postdoctoral fellow at NASA Goddard Space Flight Center and the lead author of the paper, entitled "MESSENGER orbital observations of large-amplitude Kelvin-Helmholtz waves at Mercury's magnetopause."
"You can, for example, sometimes see these waves develop on the upper edge of clouds, where they manifest as rolled-up vortices. Kelvin-Helmholtz waves can also be seen in Saturn's atmosphere, where they can develop at the boundary between the counter-streaming gas in the belts and the zones, the dark and bright bands seen across the planet," says Sundberg.
In space plasmas, such waves are of interest because they can transfer mass and energy across the boundary between two otherwise separated regions. At Mercury, the boundary is between the relatively dense and fast-streaming solar wind and the more rarified magnetosphere.
The existence of KH-waves at Mercury was confirmed during MESSENGER's third Mercury flyby. However, the observations left several questions unanswered. "These waves had been seen at Earth and Saturn, so we expected that we might see them at Mercury," Sundberg says. "But to fully understand these waves, how they develop, and how they differ from the ones found at Earth and Saturn, we needed more measurements."
The most recent observations were taken during the first 88 days of MESSENGER's time in orbit. In six different sets of magnetic field measurements made by the orbiter as it passed through Mercury's magnetopause, the boundary that separates the planet's magnetosphere from the shocked solar wind plasma in the surrounding magnetosheath, Sundberg and his colleagues were able to observe the magnetic field oscillations characteristic of fully developed KH waves.
"The waves are more frequent, are larger in amplitude, and first appear much closer to the dayside subsolar point than expected, but only on the post-noon or dusk side of the magnetopause," explains Sundberg. "Moreover, magnetic disturbances arising from the KH waves are seen over large parts of the dayside magnetosphere."
"These characteristics mean that the KH waves develop more readily and are much more important for mass and energy transfer from the solar wind into the magnetosphere than we had imagined, and there is also a dawn-dusk asymmetry in how they develop," Sundberg says. "MESSENGER's extended mission will allow us to look into remaining questions, such as why the waves are seen on the planet's dusk side but not the dawn side."
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and entered orbit about Mercury on March 17, 2011 (March 18, 2011 UTC), to begin a yearlong study of its target planet. MESSENGER's extended mission began on March 18, 2012. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
MESSENGER Gains Deputy Principal Investigator - May 8, 2012
Vancouver, B.C. -- Larry Nittler, a staff scientist in the Department of Terrestrial Magnetism of the Carnegie Institution of Washington, has been named deputy principal investigator of the MESSENGER mission. MESSENGER Principal Investigator Sean Solomon, of CIW, delivered the announcement this morning at the first plenary of the 26th meeting of the MESSENGER Science Team meeting in Vancouver, B.C.
Solomon, a research scientist and director emeritus at CIW, has led NASA's orbiting exploration of the planet Mercury since its inception. In July, he will assume the directorship of Columbia University's Lamont-Doherty Earth Observatory.
Nittler received a bachelor's degree in Physics from Cornell University in 1991, and a Ph.D. in Physics from Washington University in 1996. After a two-year postdoctoral fellowship at CIW, he took a position as an astrophysicist at NASA's Goddard Space Flight Center, where he worked on the Near Earth Asteroid Rendezvous mission to the asteroid 433 Eros. His analysis of NEAR measurements helped provide the first chemical analyses of a minor planet.
Nittler returned to Carnegie as a staff scientist in 2001. In addition to remote-sensing geochemical measurements, his research focuses on the laboratory study of extraterrestrial materials, including meteorites and interplanetary dust particles, to understand the formation of the solar system, the galaxy, and the universe and to identify the materials involved. In particular, he has led investigations of the analysis of samples returned by NASA's Stardust and Genesis missions.
"I'm delighted that Larry has agreed to shoulder new responsibilities for the MESSENGER mission," says Solomon. "He's been a Participating Scientist on MESSENGER for the past five years, he's served as deputy chair of the Science Team's Geochemistry Discipline Group for the past four, and he is leading the analysis of X-Ray Spectrometer observations of Mercury's surface composition. That he is now taking on a still larger role will enable a smooth transition in the partitioning of mission management tasks even as I assume additional duties in a new position."
"I'm honored and excited to take on this expanded role in MESSENGER," says Nittler. "It's a wonderful opportunity to help ensure the continued success of a ground-breaking planetary mission."
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and entered orbit about Mercury on March 17, 2011 (March 18, 2011 UTC), to begin a yearlong study of its target planet. MESSENGER's extended mission began on March 18, 2012. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
This week, MESSENGER's Mercury Dual Imaging System delivered the 100,000th image of Mercury since the spacecraft entered into orbit around the planet on March 18, 2011. The instrument — one of seven aboard the spacecraft — has globally mapped the planet in high-resolution monochrome images and in color images through eight of its color filters, uncovering a new view of Mercury and shedding light on the planet's geologic history.
"That our inventory of orbital images of Mercury is now expressed in six figures constitutes an important footnote in the history of solar system exploration," offers MESSENGER Principal Investigator Sean Solomon, of the Carnegie Institution of Washington. "The MESSENGER mission has at last provided us a view of the innermost planet that is fully global, multispectral, and at a range of illumination conditions. Moreover, we are steadily building a library of targeted high-resolution images that allow us to view features and discern geological processes in unprecedented detail."
Because of Mercury's proximity to the Sun and its slow rotation, designing an imaging system for an orbital mission presented quite a challenge, says MDIS Instrument Engineer Ed Hawkins of the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Md.
"The sunshade protects the spacecraft from direct solar illumination, but we knew it would constrain a camera's range of pointing," Hawkins says. "So, we had to come up with a system that would be able to capture the required observations of the planet, maintain the thermal safety requirements and not jeopardize the safety of the spacecraft.
"We finally came up with the idea for a pivoting mechanism that gave the instrument an extra degree of freedom, allowing it to obtain extra observations even when the spacecraft — and the rest of the instruments — were facing away from the planet."
The system has exceeded the team's expectations, he says. "We obtained images of Earth and Venus, but those were primarily to test the instrument. We used fairly simple spacecraft pointing options and exercised basic MDIS exposure control and compression options," he says. But the instrument's performance during the first flyby of Mercury in January 2008 was the first demonstration of the instrument's full capabilities.
"When we received that first image after the first flyby, it confirmed for us that the imaging system we designed was working, and since then the camera has been operating flawlessly," he says.
Nori Laslo, MESSENGER's Deputy Payload Operations Manager and MDIS Instrument Sequencer, says she can remember when this point "still seemed eons away.
"To have now successfully completed our primary mission, entered our extended mission, and surpassed 100,000 images is spectacular and really speaks to the ability of the MESSENGER team to work as a unit to tackle from all sides whatever challenges are encountered," says Laslo of APL. "The team is made up of people with many different backgrounds, including engineers, scientists, analysts, sequencers, flight controllers, software developers, information technology specialists, managers, and administrative support, among others. Everyone brings different expertise and insight to the table. So the milestone of 100,000 images from orbit is really a group achievement, a product of our combined efforts to make the MESSENGER mission a success."
The 100,000 images from Mercury's orbit constitute an important milestone, says MDIS Instrument Scientist Nancy Chabot, of APL. But there is still much more to come. "New images are returned from Mercury orbit on nearly a daily basis, and scientists around the world are studying these images to decipher Mercury's history and evolution."
Track the MESSENGER mission as MDIS begins to acquire the next 100,000 images from Mercury orbit by going online http://messenger.jhuapl.edu.
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and entered orbit about Mercury on March 17, 2011 (March 18, 2011 UTC), to begin a yearlong study of its target planet. MESSENGER's extended mission began on March 18, 2012. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
The International Astronomical Union (IAU) recently approved a proposal from the MESSENGER Science Team to assign 23 new names to impact craters on Mercury. The IAU has been the arbiter of planetary and satellite nomenclature since its inception in 1919. In keeping with the established naming theme for craters on Mercury, all of the newly designated features are named after famous deceased artists, musicians, or authors.
The newly named craters include:
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and entered orbit about Mercury on March 17, 2011 (March 18, 2011 UTC), to begin a yearlong study of its target planet. MESSENGER's extended mission began on March 18, 2012. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
MESSENGER mission controllers at the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Md., conducted the second of two maneuvers required to reduce the spacecraft's orbital period about Mercury. The first maneuver, completed on Monday, shortened the orbital period from 11.6 to 9.1 hours and consumed the remaining oxidizer, one of two propellants that fuel the higher-efficiency large thruster. With today's maneuver, accomplished with the spacecraft's four medium-sized thrusters, MESSENGER is now in the 8-hour orbit from which it will operate for the next year.
MESSENGER was 133 million kilometers (83 million miles) from Earth when the 4-minute maneuver began at 7:05 p.m. EDT. Mission controllers at APL verified the start of the maneuver 7 minutes and 23 seconds later, after the first signals indicating spacecraft thruster activity reached NASA's Deep Space Network tracking station in Canberra, Australia.
The shorter orbit will allow MESSENGER's science team to address new questions about Mercury's composition, geological evolution, and environment that were raised by discoveries made during the first year of orbital operations.
"For instance," says APL's Patrick Peplowski, "during the first year of orbital operations, MESSENGER's Gamma-Ray Spectrometer and X-Ray Spectrometer provided the first measurements of the abundances of many elements on Mercury's surface, including magnesium, sulfur, calcium, and potassium. The eight-hour orbit gives us more observing time at low altitudes, which will permit measurements of variations in surface composition on shorter spatial scales. Such information will give us new insight into the chemical and geological processes by which Mercury's crust was formed."
An animation of the maneuvers that guided MESSENGER into its new orbit is available online at ../Explore/media/animations/OCM7and8_transition_to_8_hour_orbit.mov.
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and entered orbit about Mercury on March 18, 2011 (UTC), to begin its primary mission – a yearlong study of its target planet. MESSENGER's extended mission began on March 18, 2012. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
MESSENGER Adjusts Orbit for a Closer Look at Mercury - April 16, 2012
The MESSENGER mission successfully completed the first of two maneuvers designed to reduce the spacecraft's orbital period about Mercury. This new trajectory will pave the way for more detailed measurements and targeted observations of the Sun's closest neighbor.
The spacecraft was 124 million kilometers (77 million miles) from Earth when the 188-second maneuver began at 3:13 p.m. EDT. Mission controllers at the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Md., verified the start of the maneuver 6 minutes and 53 seconds later, when the first signals indicating spacecraft thruster activity reached NASA's Deep Space Network tracking station in Goldstone, Calif.
This maneuver -- which adjusted the orbital period from 11 hours, 36 minutes to 9 hours, 5 minutes -- was designed to deplete the remaining oxidizer of the spacecraft's propulsion system in a final firing of the large bi-propellant thruster. A second maneuver, scheduled for the evening of April 20, will use the spacecraft's monopropellant system to complete the transition to an 8-hour orbit.
The strategy to complete this transition involves the execution by the MESSENGER flight team of carefully planned command sequences, says MESSENGER Mission Design Lead James McAdams of APL. "The first orbit-correction maneuver consumed the remaining oxidizer, which is one of two propellants used for the higher-efficiency large thruster," he explains. Although such an "oxidizer depletion" maneuver is not uncommon, new procedures had to be developed and tested to make this MESSENGER critical event possible and safe to perform.
After Friday's maneuver, the 8-hour orbit will remain highly eccentric, with MESSENGER travelling between 278 kilometers (172 miles) and 10,314 kilometers (6,409 miles) above Mercury's surface. Reducing the orbital period will increase from two to three the number of revolutions the spacecraft will make about the planet each day, increasing the time that the spacecraft will spend closer to the surface, says MESSENGER Mission Systems Engineer Eric Finnegan, of APL.
The additional time at lower altitude, he says, will enhance the science return. It will amplify the effectiveness of the high-energy spectrometers used to determine the composition of the planet's surface and will increase the number of altitude profiles that the laser altimeter will be able to make in the northern hemisphere of the planet, allowing for more detailed topographic maps. Operations at this lower altitude will also enable higher-resolution imaging of Mercury's southern hemisphere.
"The MESSENGER engineering and operations teams have once again made a critical maneuver look easy," says MESSENGER Principal Investigator Sean C. Solomon, of the Carnegie Institution of Washington. "The Science Team is now looking forward to being able to address a host of scientific questions on the composition, geological evolution, and environment of Mercury that have been raised by earlier orbital observations. With our new orbit, it feels as though we're embarking on a new mission."
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and entered orbit about Mercury on March 17, 2011 (March 18, 2011 UTC), to begin a yearlong study of its target planet. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
MESSENGER Images Debut on "The Big Bang Theory" - April 5, 2012
Tonight, images from MESSENGER's Mercury Dual Imaging System will make their debut on the CBS sitcom, "The Big Bang Theory." The award-winning comedy centers on five characters: roommates Sheldon Cooper and Leonard Hofstadter, two physicists who work at the California Institute of Technology; and Sheldon's and Leonard's equally geeky and socially awkward friends and co-workers, aerospace engineer Howard Wolowitz and astrophysicist Rajesh Koothrappali; and Penny, a blonde waitress and aspiring actress who lives across the hall.
Much of the show focuses on science, particularly physics. The characters frequently banter about scientific theories or news and make science-related jokes.
"The MESSENGER team is thrilled by the decision of the producers and writers of 'The Big Bang Theory' to weave some of the spacecraft's latest images of Mercury into this week's episode," says MESSENGER Principal Investigator Sean Solomon, of the Carnegie Institution of Washington. "We look forward to seeing how the images figure in the story line and camera shots, and we hope that interest in the MESSENGER mission is broadened by this exposure on one of the most popular series now on television."
MESSENGER's images will appear in an episode entitled, The Hawking Excitation. When Wolowitz gets to work with Stephen Hawking, Sheldon is willing to do anything to meet his hero. The show airs tonight at 8:00 p.m. EDT on CBS!
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and entered orbit about Mercury on March 17, 2011 (March 18, 2011 UTC), to begin a yearlong study of its target planet. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
MESSENGER App Now Available - March 23, 2012
The MESSENGER team has launched a free app that brings you inside NASA's history-making study of Mercury - the first images of the entire planet, along with the detailed data on Mercury's surface, geologic history, thin atmosphere, and active magnetosphere that MESSENGER sends back every day.
Now available in the iTunes App Store, "MESSENGER: NASA's Mission to Mercury" brings users the latest news and pictures from the mission, as well as details on the spacecraft and science instruments, and offers access to educational programs and activities.
Circle the innermost planet aboard MESSENGER, the first mission to orbit Mercury. Examine a detailed view of the MESSENGER spacecraft and its science instruments, browse the latest news and images, or trace the spacecraft's path over Mercury as it scans the scorched surface of the Sun's closest planetary neighbor. Can you take the heat?
Main Features Include:
News
Get up-to-the-minute reports from the MESSENGER Web News Center and Twitter feed.
Media
Have the "Mercury Image of the Day" sent straight to your device; flip through hundreds of stunning pictures of Mercury taken by the spacecraft's cameras; watch videos that trace MESSENGER's 4.9-billion mile journey to Mercury that included six planetary flybys and 15 trips around the Sun.
Information
Tour the robust MESSENGER spacecraft and science payload; see what MESSENGER was designed to learn about Mercury; pick up some quick facts about the mission and its planetary target.
Tools
Follow MESSENGER as it loops around Mercury; pinpoint its location over the surface; see how much time remains in its current, 12-hour orbit.
Education (iPad only)
Use the interactive QuickMap to view areas on Mercury observed or targeted for hi-resolution observation by MESSENGER instruments, locate craters and other "named" surface features, and explore detailed global and regional images.
The new app is available for download at http://itunes.apple.com/us/app/messenger-nasas-mission-to/id510144229?ls=1&mt=8.
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and entered orbit about Mercury on March 18, 2011 (UTC), to begin a yearlong study of its target planet. MESSENGER's extended mission began on March 18, 2012. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
MESSENGER Provides New Look at Mercury's Landscape, Metallic Core, and Polar Shadows - March 21, 2012
MESSENGER completed its one-year primary mission on March 17. Since moving into orbit about Mercury a little over one year ago, the spacecraft has captured nearly 100,000 images and returned data that have revealed new information about the planet, including its topography, the structure of its core, and areas of permanent shadow at the poles that host the mysterious polar deposits.
The latest findings are presented in two papers published online in Science Express today, and in 57 papers presented this week at the 43rd Lunar and Planetary Science Conference in The Woodlands, Texas. Team members at the meeting will also preview MESSENGER's extended mission, set to run to March 2013. Presentation materials are available on the web at http://messenger.jhuapl.edu/news_room/presscon11.html.
"The first year of MESSENGER orbital observations has revealed many surprises," says MESSENGER Principal Investigator Sean C. Solomon, of the Carnegie Institution of Washington. "From Mercury's extraordinarily dynamic magnetosphere and exosphere to the unexpectedly volatile-rich composition of its surface and interior, our inner planetary neighbor is now seen to be very different from what we imagined just a few years ago. The number and diversity of new findings being presented this week to the scientific community in papers and presentations provide a striking measure of how much we have learned to date."
Mercury's Landscape
Ranging observations from MESSENGER's Mercury Laser Altimeter (MLA) have provided the first-ever precise topographic model of the planet's northern hemisphere and characterized slopes and surface roughness over a range of spatial scales. From MESSENGER's eccentric, near-polar orbit, the MLA illuminates surface areas as wide as 15 to 100 meters, spaced about 400 meters apart.
The spread in elevations is considerably smaller than those of Mars or the Moon, notes MESSENGER Co-investigator Maria T. Zuber, author of one of the papers published in Science Express. According to Zuber, of the Massachusetts Institute of Technology, the most prominent feature is an extensive area of lowlands at high northern latitudes that hosts the volcanic northern plains. Within this lowland region is a broad topographic rise that formed after the volcanic plains were emplaced.
At mid-latitudes, the interior of the Caloris impact basin -- 1,500 kilometers wide -- has been modified so that part of the basin floor now stands higher than the rim, Zuber says. "The elevated portion of the floor of Caloris appears to be part of a quasi-linear rise that extends for approximately half the planetary circumference at mid-latitudes," she writes. "Collectively, these features imply that long-wavelength changes to Mercury's topography occurred after the earliest phases of the planet's geological history."
A Surprising Core
Scientists have also come up with the first precise model of Mercury's gravity field which, when combined with the topographic data and earlier information of the planet's spin state, shed light on the planet's internal structure, the thickness of its crust, the size and state of its core, and its tectonic and thermal history.
Mercury's core is huge for the planet's size, about 85% of the planetary radius, even larger than previous estimates. The planet is sufficiently small that at one time many scientists thought the interior should have cooled to the point that the core would be solid. However, subtle dynamical motions measured from Earth-based radar combined with parameters of the gravity field, as well as observations of the magnetic field that signify an active core dynamo, indicate that Mercury's core is at least partially liquid.
"MESSENGER's observations of the gravity field have let us peer inside Mercury and get the first good look at its largest component -- the core," says Case Western Reserve University's Steven A. Hauck II, coauthor of one of the papers published in Science Express.
Scientists sought to unravel the mystery of the size and state of Mercury's core by studying its effect on long-wavelength variations in the planet's gravity field, and recent results point to a much different interior structure for Mercury from that expected.
"Mercury's core may not look like any other terrestrial planetary core," Hauck says. "The structure certainly is different from that of Earth, which has a metallic, liquid outer core sitting above a solid inner core. Mercury appears to have a solid silicate crust and mantle overlying a solid, iron sulfide outer core layer, a deeper liquid core layer, and possibly a solid inner core."
These findings will have implications for how Mercury's magnetic field is generated and for understanding how the planet evolved thermally, Hauck adds.
Polar Shadows
A chief goal of MESSENGER's primary mission was to understand the nature of the radar-bright deposits at the poles of Mercury. The leading proposal since the deposits were discovered has been that radar-bright material consists dominantly of frozen water ice.
"We've never had the imagery available before to see the surface where these radar-bright features are located," says Nancy L. Chabot, instrument scientist for MESSENGER's Mercury Dual Imaging System (MDIS) at the Johns Hopkins University Applied Physics Laboratory (APL). "MDIS images show that all the radar-bright features near Mercury's south pole are located in areas of permanent shadow, and near Mercury's north pole such deposits are also seen only in shadowed regions, results consistent with the water-ice hypothesis."
This finding is not definitive proof that those deposits are water ice, says Chabot, who is presenting her results at LPSC. And some of the radar-bright deposits are located in craters that provide thermally challenging environments to the water-ice theory. For instance, for the radar-bright material in many of the craters to be water ice would require that there be a thin layer of insulation to keep it colder than the surface, Chabot says.
But the MDIS images, combined with ongoing analysis of data from MESSENGER's Neutron Spectrometer and the MLA, will provide a more complete picture of the nature of the deposits.
Extending the Discoveries
MESSENGER's second year at Mercury will build upon these and other results from the primary mission phase, emphasizes MESSENGER Project Scientist Ralph L. McNutt Jr., of APL. "The second year of orbital operations will not be a simple continuation of the primary mission," he says. "Extended mission themes will include more comprehensive measurement of the magnetosphere and exosphere during a period of more active Sun, greater focus on observations at low spacecraft altitudes, and a greater variety of targeted observations."
"MESSENGER has already fundamentally changed our view of this innermost planet," he adds. "With the extension of the MESSENGER mission, many more discoveries can be expected."
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and entered orbit about Mercury on March 18, 2011 (UTC), to begin its primary mission â€" a yearlong study of its target planet. MESSENGER's extended mission began on March 18, 2012. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
On March 17, 2012, MESSENGER successfully wrapped up a year-long campaign to perform the first complete reconnaissance of the geochemistry, geophysics, geologic history, atmosphere, magnetosphere, and plasma environment of the solar system's innermost planet. The following day, March 18, 2012, marked the official start of an extended phase designed to build upon those discoveries.
What MESSENGER has accomplished since its launch in August 2004 is "amazing," says MESSENGER Mission Systems Engineer Eric Finnegan, of the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Md.
"Six plus years of cruise operations, capped by a year of nearly flawless orbital operations, with an additional year of scientific return ahead in the harsh environment at 0.3 astronomical units (27,886,766 miles) from the Sun," he begins, checking off the list of mission accomplishments. All this "achieved with a 1,000 kg satellite, designed, built, and launched in less than four years for a total mission cost of less than $450 million."
"This is a testament to the hundreds of innovative, talented, and dedicated engineers, technicians, and support personnel here at APL and around the world who contributed to this mission," he continues. "Before selection many said that the MESSENGER mission to inject a spacecraft into orbit around Mercury and map, in-detail, the surface and surrounding environment could not be achieved within the constricts of NASA's Discovery program. The APL team did it!"
MESSENGER's three flybys of Mercury solved the decades-old question of whether there are volcanic deposits on the planet's surface. But the detailed character and global distribution of volcanic materials remained poorly known until the arrival of MESSENGER in orbit about Mercury. MESSENGER orbital images have revealed volcanic vents measuring up to 25 kilometers (15.5 miles) across that appear to have once been sources for large volumes of very hot lava that, after eruption, carved valleys and created teardrop-shaped ridges in the underlying terrain.
Also noteworthy is the discovery from measurements of Mercury's gravity field that the planet has an unexpectedly complex internal structure, a finding that will be discussed in a paper to be published by Science Express on March 21, 2012, and at a press conference at the 43rd Lunar and Planetary Science Conference in The Woodlands, Texas.
"The last year has been a busy and rewarding one for the MESSENGER project," says MESSENGER Project Manager Peter Bedini, of APL in Laurel, Md. "As the engineering and operations teams closely monitored the spacecraft's response to Mercury's seasons, the science team was busy analyzing data and filling gaps in our understanding of the planet. Science results from the first year of orbital operations have influenced the observation plan for the second year, which we expect to be as busy as the first, and hope to be as rewarding."
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and entered orbit about Mercury on March 17, 2011 (March 18, 2011 UTC), to begin its primary mission â€" a yearlong study of its target planet. MESSENGER's extended mission began on March 18, 2012. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
MESSENGER Team Delivers Data from First Full Mercury Solar Day to Planetary Data System - March 8, 2012
Data collected during MESSENGER's third through sixth month in orbit around Mercury were released to the public today by the Planetary Data System (PDS), an organization that archives and distributes all of NASA's planetary mission data. With this release, data are now available to the public for the first full Mercury solar day of MESSENGER orbital operations.
Calibrated data from all seven of MESSENGER's science instruments, plus radio science data from the spacecraft telecommunications system, are included in this release. The science results have shed light on many aspects of Mercury, including its global magnetic field, the dynamics of its exosphere, its surface composition, its geological evolution, and its interior structure.
The images included in this release provide monochrome views at 250 meters per pixel and eight-color image sets at 1 kilometer per pixel. Apart from small gaps, many of which have already been filled by subsequent imaging, these images cover the entire planet under lighting conditions ideal either for assessing the form of Mercury's surface features or for determining the color and compositional variations across the planet.
For more than two decades, NASA has required all of its planetary missions to archive data in the PDS, an active archive that makes available well-documented, peer-reviewed data to the research community. The PDS includes eight university/research center science teams, called discipline nodes, each of which specializes in a specific area of planetary data. The contributions from these nodes provide a data-rich source for scientists, researchers, and developers.
All of the MESSENGER data archived at the PDS thus far are available at http://pds.nasa.gov. As of this release, MESSENGER will have delivered 1.7 terabytes of raw and calibrated data to the PDS, including more than 62,355 images (of which 49,275 are from orbit). The team will submit four more PDS deliveries at six-month intervals from MESSENGER's primary orbital mission and its extended mission.
The MESSENGER team has created a software tool with which the public can view data from this delivery. ACT-REACT-QuickMap provides an interactive Web interface to MESSENGER data. Developed by Applied Coherent Technology Corporation, the software allows users to examine global mosaics constructed with high-resolution images from this and previous PDS deliveries.
The tool also provides weekly updates of coverage for surface-observing instruments, as well as the status of specially targeted MDIS observations. Information is also available that can be used to locate MESSENGER data products at the PDS. QuickMap can be accessed via links on each of the MESSENGER websites at http://messenger.jhuapl.edu/ and http://www.nasa.gov/messenger. The MDIS mosaics can be downloaded from ../Explore/Images.html#global-mosaics. 

"This latest release marks another important milestone in the sharing of MESSENGER data with planetary scientists and the public," adds MESSENGER Principal Investigator Sean Solomon, of the Carnegie Institution of Washington. "Mercury has presented us with many mysteries to date, and solving those mysteries will take new ideas and new analyses from throughout the scientific community."
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and entered orbit about Mercury on March 18, 2011 (UTC), to begin its primary mission â€" a yearlong study of its target planet. MESSENGER's extended mission begins on March 18, 2012. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
MESSENGER Modifies Orbit to Prepare for Extended Mission - March 2, 2012
MESSENGER successfully completed an orbit-correction maneuver this evening to lower its periapsis altitude - the lowest point of MESSENGER's orbit about Mercury relative to the planet's surface - from 405 to 200 kilometers (251 to 124 miles). This is the first of three planned maneuvers designed to modify the spacecraft's orbit around Mercury as science operations transition from MESSENGER's primary orbital mission to its extended mission.
MESSENGER's orbit around Mercury is highly eccentric, taking it from 200 kilometers (124 miles) above Mercury's surface to 15,200 kilometers (9,445 miles) altitude every 12 hours. Since orbit insertion nearly one year ago, spacecraft operators at the Johns Hopkins Applied Physics Laboratory (APL) in Laurel, Maryland, conducted five earlier maneuvers to counter the perturbing forces that pull MESSENGER away from its preferred observing geometry, including those arising from solar gravity and Mercury's slight oblateness (the flattening of its spherical shape at the planet's poles).
For this latest orbit adjustment, MESSENGER was 148 million kilometers (92 million miles) from Earth when the 171-second maneuver, which used all four of the medium-sized monopropellant thrusters on the deck opposite most of the science instruments, began at 8:44 p.m. EST. APL mission controllers verified the start of the maneuver 8 minutes and 12 seconds later, when the first signals indicating spacecraft thruster activity reached NASA's Deep Space Network tracking station near Canberra, Australia.
In mid-April the team will conduct two additional maneuvers designed to reduce the period of MESSENGER's orbit around Mercury from 12 to eight hours. According to MESSENGER Principal Investigator Sean Solomon, of the Carnegie Institution of Washington, "This reduction in orbital period will mean that MESSENGER spends a greater fraction of its time close to Mercur's surface than during the primary mission that is now nearing a successful completion. Moreover, the accomplishment of the global mapping carried out during the primary mission will free many of MESSENGER's instruments for a new mix of measurements to address a fresh set of scientific objectives designed to answer questions raised by the findings from orbital observations to date."
"The eight-hour orbit will provide 50% more low-altitude observation opportunities of Mercury's north polar regions, including permanently shadowed craters," explains MESSENGER Mission Design Lead Jim McAdams of APL. "A one-third reduction in maximum altitude relative to the 12-hour orbit will enable higher-resolution imaging of the southern hemisphere."
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and entered orbit about Mercury on March 18, 2011 (UTC), to begin its primary mission â€" a yearlong study of its target planet. MESSENGER's extended mission begins on March 18, 2012. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
Software Enables Efficient Planning of MESSENGER Observations - February 3, 2012
SciBox, a scientific planning software package, has proven critical to the success of the MESSENGER mission to Mercury. With completion of the design of all primary-mission observations -- including more than 70,000 images and millions of spectral observations -- the SciBox software tool has substantially increased, relative to original expectations, the scientific return from the first year of Mercury orbital observations. The spacecraft team is now adapting the system to develop the best plan for MESSENGER's extended mission, which begins next month.
Software engineers at the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Md., designed SciBox for the simulation and planning of mission scientific operations and for the generation of spacecraft and instrument commands. “It is a flexible, adjustable suite of mission-simulation and command-generation tools that models spacecraft performance with high fidelity,†explains APL's Teck Choo, the creator and architect of SciBox.
SciBox developers worked with the scientists responsible for MESSENGER's investigations to insert the requirements for all scientific observations into the software's decision routines. During a planning run, SciBox examines the entire mission, locating the best opportunity for each scientific observation. Then, using a set of intertwined priorities constructed to minimize interference among observations, SciBox schedules the full set of observations for the entire mission.
Once the science and engineering teams verify the plan, SciBox produces the instrument commands, which are combined with telecommunication and power commands and then converted to binary format for transmission to the spacecraft. Because spacecraft pointing is integral to the observation plan, SciBox also plans attitude control maneuvers and produces those commands.
The SciBox planning system has increased the scientific return from MESSENGER in several ways. First, it has reduced the complexity involved in combining the more than 30 different sets of observations from the seven instruments and radio science. “By hand, this intractable problemâ€"to find a fully integrated schedule that accommodates all observations â€" would be nearly impossible to solve,†states Mark Perry, the science lead for SciBox development. “With SciBox, the scientists can levy any and all types of requirements and constraints on the observations, no matter how intricate, and the SciBox implementation team can create an observing sequence to satisfy them.â€
SciBox also helped the team evaluate options. “With SciBox, scientists and planners can modify the observational parameters and evaluate the effect on the entire mission schedule,†Perry says. “Part of SciBox's output is an extensive set of reports that includes detailed lists, summary statistics, and hundreds of plots that facilitate evaluation of improvements and modifications. With that valuable information, MESSENGER scientists can conduct trades to identify the best approach.â€
SciBox can also respond quickly to changes in the mission or requirements. “SciBox can re-plan an entire mission in three hours, including the re-integration of all observations, the generation of commands, and the completion of reports,†says Choo. “If the orbit is slightly different from that expected, or if an instrument's optimal observing parameters change during the course of the mission, then we modify SciBox and re-run it.â€
These same SciBox features have also reduced the risks involved in achieving overall mission objectives. “By planning all the mission observations at once, scientists need not estimate the long-range effects of their requirements,†Perry says. Many of the observing variables are run-time parameters, enabling trade studies without modifying the SciBox code, he explains. With SciBox, planners can also easily investigate the effects of problems and then modify SciBox to develop a plan that is less sensitive to such problems. This rapid response capability minimizes the effect of mission changes by quick re-planning of the full mission.
The SciBox tool continues to evolve. Indeed, one of its advantages is the ease with which it accommodates changes. During MESSENGER's yearlong primary mission, as the science team has identified new observing opportunities, capability has been added to generate new and improved observations.
For the extended mission, the team developed a version of SciBox that incorporates all of the extended-mission observing requirements defined by MESSENGER's science team. The SciBox developers examined strategies for accomplishing the new observations and then worked with the scientists to resolve conflicts and ensure that all requirements are met. The result, endorsed by the science team and scheduled to go into effect in March, is a packed plan that achieves a scientific return that exceeds extended mission requirements.
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and entered orbit about Mercury on March 17, 2011 (March 18, 2011 UTC), to begin a yearlong study of its target planet. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
A Christmas Crater on Mercury - December 22, 2011
The crater at the center of Wednesday's MESSENGER image of the day is named Dickens, after Charles Dickens, the English novelist who lived from 1812 to 1870. Among Dickens' most famous works is A Christmas Carol, the story of miserly Ebenezer Scrooge and his tortured journey to a more humanitarian and generous nature.
This image was acquired as part of the Mercury Dual Imaging System's (MDIS) high-resolution surface morphology base map. The surface morphology base map will cover more than 90% of Mercury's surface with an average resolution of 250 meters per pixel (0.16 miles per pixel). Images acquired for the surface morphology base map typically have off-vertical Sun angles (i.e., high incidence angles) and visible shadows so as to reveal clearly the topographic form of geologic features.
Since entering orbit around Mercury on March 18, 2011, the MDIS has beamed back more than 70,000 images of the surface of the planet. The mission's imaging team has been releasing at least one new image every weekday. They are available online here. During the one-year primary mission, MDIS is scheduled to acquire more than 75,000 images in support of MESSENGER's science goals.
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and entered orbit about Mercury on March 17, 2011 (March 18, 2011 UTC), to begin a yearlong study of its target planet. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
MESSENGER Among Discover Magazine's Top 100 Stories of 2011 - December 16, 2011
Discover magazine has named the MESSENGER mission one of the top 100 stories of 2011. "The 100 stories here capture scientific curiosity in all its stages: provocative early results, long-sought confirmation, and many steps in the iterative process of testing theory against observation and vice versa," wrote Discover Editor-in-Chief Corey Powell in the Editor's Note for the January/February 2012 issue of the magazine.
MESSENGER came in at 25 among the 100. This honor caps off a year of accomplishment for the spacecraft, which entered orbit around Mercury on March 18, 2011, and has since sent back images and other data that have transformed our scientific understanding of the planet closest to the Sun.
The magazine's article on MESSENGER, entitled "Mercury's New Face," was written by noted author Dava Sobel. Sobel was among the visitors to the Johns Hopkins University Applied Physics Laboratory in Laurel, Md., on the occasion of Mercury orbit insertion, and she wrote her story as a first-hand account of that evening.
"The MESSENGER team is honored to be recognized by Discover magazine for our spacecraft's amazing year," says MESSENGER Principal Investigator Sean Solomon, of the Carnegie Institution of Washington. "It was particularly special that Discover assigned a writer with the story-telling ability of Dava Sobel to cast the mission's challenges and opportunities in compelling terms. With NASA's recent approval of a MESSENGER Extended Mission, we can look forward to another year of scientific surprises at Mercury."
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and entered orbit about Mercury on March 17, 2011 (March 18, 2011 UTC), to begin a yearlong study of its target planet. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
MESSENGER Team Presents Latest Mercury Findings at AGU Fall Meeting - December 5, 2011
Members of the MESSENGER team will present a broad range of findings from the spacecraft's orbital investigation of Mercury during the 2011 Fall Meeting of the American Geophysical Union (AGU), which takes place this week, December 5-9, in San Francisco. In 63 oral and poster presentations spanning 13 technical sessions, team scientists will report on the analysis and interpretation of observations made by MESSENGER's instruments since the spacecraft entered orbit around Mercury in March 2011.
The majority of the MESSENGER papers will be given in three special sessions on December 8. Those papers will report new findings on the topography and gravity field of Mercury's northern hemisphere, Mercury's internal structure and dynamics, the elemental composition of Mercury's surface, the variation of Mercury's surface spectral reflectance, Mercury's distinctive hollows, plains volcanism on Mercury, characteristics of impact craters on Mercury, deformation of Mercury's surface, Mercury's internal magnetic field, the structure and variability of Mercury's exosphere, the structure and dynamics of Mercury's magnetosphere, energetic particles and plasma ions in Mercury's vicinity, and Mercury's interplanetary environment.
MESSENGER Principal Investigator Sean Solomon will also deliver AGU's Shoemaker Lecture to provide an overview of all that's been discovered about the innermost planet.
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and entered orbit about Mercury on March 17, 2011 (March 18, 2011 UTC), to begin a yearlong study of its target planet. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
MESSENGER Recognized as "Best of What's New" by Popular Science - November 18, 2011
MESSENGER was named a winner in Popular Science magazine's 24th annual "Best of What's New" in the Aviation and Space category.
Founded in 1872, Popular Science is the world's largest science and technology magazine, with a circulation of 1.3 million and 6.8 million monthly readers. Each year, the magazine's editors review thousands of products in search of the top 100 tech innovations of the year in 11 categories: automotive, aviation & space, computing, engineering, gadgets, green tech, home entertainment, security, home tech, health and recreation. The winners—the Best of What's New—are awarded inclusion in the much-anticipated December issue of Popular Science, the most widely read issue of the year since the debut of Best of What's New in 1987.
"For 24 years, Popular Science has honored the innovations that surprise and amaze us—those that make a positive impact on our world today and challenge our views of what's possible in the future," said Mark Jannot, Editor-in-Chief of Popular Science. "The Best of What's New Award is the magazine's top honor, and the 100 winners—chosen from among thousands of entrants—represent the highest level of achievement in their fields."
"The MESSENGER team is honored to receive this recognition from Popular Science," says Principal Investigator Sean Solomon, of the Carnegie Institution of Washington. "The intensive exploration of the Sun's nearest planet has been an exhilarating adventure that we are delighted to share with the global public."
See what Popular Science had to say about MESSENGER by going online to http://www.popsci.com/bown/2011/product/nasajohns-hopkins-university-applied-physics-lab-messenger.
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and entered orbit about Mercury on March 18, 2011 UTC, to begin its primary mission—a yearlong study of its target planet. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
NASA Extends MESSENGER Mission - November 14, 2011
NASA has announced that it will extend the MESSENGER mission for an additional year of orbital operations at Mercury beyond the planned end of the primary mission on March 17, 2012. The MESSENGER probe became the first spacecraft to orbit the innermost planet on March 18, 2011.
"We are still ironing out the funding details, but we are pleased to be able to support the continued exploration of Mercury," said NASA MESSENGER Program Scientist Ed Grayzeck, who made the announcement on November 9, 2011, at the 24th meeting of the MESSENGER Science Team in Annapolis, Md.
The spacecraft's unprecedented orbital science campaign is providing the first global close-up of Mercury and has revolutionized scientific perceptions of that planet. The extended mission will allow scientists to learn even more about the planet closest to the Sun, says MESSENGER Principal investigator Sean Solomon, of the Carnegie Institution of Washington.
"During the extended mission we will spend more time close to the planet than during the primary mission, we'll have a broader range of scientific objectives, and we'll be able to make many more targeted observations with our imaging system and other instruments," says Solomon. "MESSENGER will also be able to view the innermost planet as solar activity continues to increase toward the next maximum in the solar cycle. Mercury's responses to the changes in its environment over that period promise to yield new surprises."
The extended mission has been designed to answer six scientific questions, each of which has arisen only recently as a result of discoveries made from orbit:
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and entered orbit about Mercury on March 18, 2011 (UTC) to begin its primary mission—a yearlong study of its target planet. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
MESSENGER Mission Design Lead Named American Institute of Aeronautics and Astronautics Associate Fellow - November 3, 2011
MESSENGER mission design lead engineer James McAdams has been named an Associate Fellow of the American Institute of Aeronautics and Astronautics (AIAA). To be selected for the grade of Associate Fellow an individual must be an AIAA Senior Member with at least 12 years professional experience and have been recommended by at least three AIAA members who are already Associate Fellows or Fellows.
The 2012 Associate Fellows will be honored at the AIAA Associate Fellows Dinner on Monday, January 9, 2012, at the Gaylord Opryland Resort & Convention Center, Nashville, Tennessee, in conjunction with the 50th AIAA Aerospace Sciences Meeting.
McAdams optimized the trajectory and course-correction maneuvers for MESSENGER, which required six gravity-assist flybysone of Earth, two of Venus, and three of Mercuryand five large course-correction maneuvers. These flybys and maneuvers slowed the spacecraft's speed relative to Mercury so as to enable its thrusters to place the probe into orbit around Mercury early on March 18, 2011. Since entering orbit around Mercury, MESSENGER successfully completed four of the five planned orbit-adjustment maneuvers.
Learn more about his critical role on the MESSENGER team.
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and entered orbit about Mercury on March 17, 2011 (March 18, 2011 UTC), to begin a yearlong study of its target planet. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
Fourth Orbit Adjustment Stretches MESSENGER's Orbit around Mercury - October 24, 2011
The MESSENGER spacecraft successfully completed its fourth orbit-correction maneuver today to increase the period of the spacecraft's orbit around the innermost planet from 11 hours 46 minutes to a precise 12 hours.
MESSENGER was 198 million kilometers (123 million miles) from Earth when the 159-second maneuver began at 6:12 p.m. EDT. Mission controllers at The Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Md., verified the start of the maneuver about 11 minutes, 1 second later, when the first signals indicating spacecraft thruster activity reached NASA's Deep Space Network tracking station outside Goldstone, Calif.
This is the fourth of five maneuvers planned for the primary orbital phase of the mission to keep orbital parameters within desired ranges for optimal scientific observations. MESSENGER's orbital velocity was changed by a total of 4.2 meters per second (9.4 miles per hour) to make the corrections essential for continuing the planned measurement campaigns.
Most of the instruments were placed in a passive state during the burn, but the instruments were reconfigured at 7:05 p.m. EDT to resume scientific observations of the planet.
MESSENGER Mission Systems Engineer Eric Finnegan, of APL, said the engine burn was executed as planned. "The team was well-prepared for the maneuver, and MESSENGER is right where it needs to be to continue revealing new details about Mercury," he said.
The next orbit-correction maneuver is scheduled for December 5.
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and entered orbit about Mercury on March 17, 2011 (March 18, 2011 UTC), to begin a yearlong study of its target planet. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
MESSENGER Team Presents New Mercury Findings at Planetary Conference - October 5, 2011
Nantes, France—MESSENGER scientists will highlight the latest results on Mercury from MESSENGER observations obtained during the first six months (the first Mercury solar day) in orbit. These findings will be presented October 5 in 30 papers and posters as part of a special session of the joint meeting of the European Planetary Science Congress and the Division for Planetary Sciences of the American Astronomical Society in Nantes, Frances.
Scientists will also look ahead to MESSENGER observations still to come and to the dual-spacecraft BepiColombo mission of the European Space Agency and the Japan Aerospace Exploration Agency's later this decade.
"This is the first major scientific meeting at which MESSENGER orbital observations are being presented to the scientific community," says MESSENGER Principal Investigator Sean Solomon of the Carnegie Institution of Washington. "As the first spacecraft to orbit our solar system's innermost planet, MESSENGER continues to reveal new surprises every week. It is timely to sum up what we've learned so far and to seek feedback from our international colleagues across planetary science on our interpretations to date."
After three successful flybys of Mercury, the MESSENGER spacecraft entered orbit about the innermost planet on March 18, 2011. The orbital phase of the mission is enabling the first global perspective on the planet's geology, surface composition, topography, gravity and magnetic fields, exosphere, magnetosphere, and solar-wind interaction.
Mercury's Global Magnetic Field
The magnetic and gravity fields of Mercury are the primary clues scientists have on the structure deep in the interior of the planet, which in turns helps develop general theories for how planets form and evolve. Orbital data reveal that Mercury's magnetic field is offset far to the north of the planet's center, by nearly 20% of Mercury's radius. Relative to the planet's size, this offset is much more than in any other planet, and accounting for it will pose a challenge to theoretical explanations of the field.
"Although we don't know how to explain that yet, it is no doubt an important clue to the workings of Mercury's dynamo," says Brian Anderson, MESSENGER Deputy Project Scientist and a space physicist at the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Md.
This finding has several implications for other aspects of Mercury, says Anderson, who co-authored several of the presentations in the MESSENGER session. "This means that the magnetic field in the southern hemisphere should be a lot weaker than it is in the north. At the north geographic pole, the magnetic field should be about 3.5 times stronger than it is at the south geographic pole.
"The big difference in northern and southern surface field strengths means that energetic particles, solar wind, and high-energy electrons will preferentially impact the surface in the south, and this situation should lead to asymmetries both in sources of atoms, ions, and molecules for Mercury's exosphere and in the discoloration of the surface by charged particle bombardment," he continues. "Both should occur more strongly in the south."
The Dynamics of Mercury's Exosphere
Mercury is surrounded by a tenuous exosphere of gas generated and maintained by the interaction of the space environment with the planet's surface. Measuring the composition and structure of the exosphere provides insight into how the space environment modifies the outermost layers of the planet's surface materials.
MESSENGER's observations during the flybys and orbit show that the current understanding of the nature of Mercury's exosphere is incomplete, says William McClintock, a MESSENGER mission co-investigator and senior scientist at the Laboratory for Atmospheric and Space Physics, University of Colorado, Boulder.
"They show that distinctly different source and loss processes control the populations of the major constituents of sodium, magnesium, and calcium atoms in the exosphere," says McClintock.
Before MESSENGER, the prevailing theory suggested that material was released from the dayside by solar wind and radiation. In this picture, lofted material then was carried to the nightside by solar radiation pressure. MESSENGER measurements show that magnesium and calcium in the tail region are substantially more abundant than would be expected if they were produced in this way, he points out.
New magnetic field models, derived from MESSENGER's Magnetometer data, indicate that the planet's intrinsic field can couple with the interplanetary field to direct solar wind ions to the nightside, sputtering material from non-illuminated surfaces. But that source is too weak to explain the observed concentrations. Calcium also exhibits an unexplained enhanced concentration at the equator near dawn, a pattern that appears to be a persistent feature in the exosphere. Such dawn enhancements are not observed for magnesium, which is chemically similar to calcium.
The Evolution of Mercury's Geological and Surface Composition
After its first Mercury solar day in orbit, MESSENGER has nearly completed two of its primary global imaging campaigns: a monochrome map at 250 meters per pixel and an eight-color, 1 kilometer per pixel color map. Apart from small gaps, which will be filled in during the next solar day, these maps cover the entire planet under uniform lighting conditions ideal for assessing the form of Mercury's surface features as well as the color and compositional variations across the planet.
Flybys of Mercury by the MESSENGER and Mariner 10 spacecraft showed broad expanses of plains across the planet. There was strong evidence for a volcanic origin of many of these plains, indicating that volcanism played an important role in shaping Mercury's crust; but large regions of the planet remained unmapped, and the origin of many plains units had until now remained ambiguous.
"With images from MESSENGER's orbital mapping campaigns, as well as targeted high-resolution images, we can now begin to assess the origin of plains on a global basis, and—when combined with data from MESSENGER's X-Ray Spectrometer—their compositional variation," says Brett Denevi, a planetary scientist in APL's Space Department. "We find that volcanic rocks dominate much of Mercury's crust, even in regions that are geologically complex and where impact cratering has destroyed many of the original surface features."
The X-Ray Spectrometer collects compositional information averaged over relatively large regions on Mercury's surface, and signals diagnostic of the heavier elements are received only during times of high solar activity. For regions where geologic mapping and detailed compositional information are both available, many of the large-scale volcanic units on Mercury are seen to be basaltic. Basalts are common volcanic rocks on Earth and the Moon.
Variations in Surface Reflectance Spectra
Over the course of the first solar day in orbit, the Visible and Infrared Spectrograph (VIRS) channel of the Mercury Atmospheric and Surface Composition Spectrometer (MASCS) obtained over one million spectra of the surface from near one pole to the other and spanning all longitudes. VIRS observed all the major geologic units and structures, from large basins to small fresh-looking craters, and from average pains to hollows and possible pyroclastic materials. Whereas the Mercury Dual Imaging System highlights the morphology and broad color characteristics of these materials, VIRS reveals greater details of the reflective properties of surface materials.
"One surprise that's been with us since the flybys is the apparent lack of iron in the silicate minerals of the rocks on the surface of the planet," says APL's Noam Izenberg, Instrument Scientist for the MASCS instrument on MESSENGER.
"In rock-forming silicates, the primary materials of most planetary crusts, iron shows up as a characteristic absorption at infrared wavelengths, but such features have been completely absent in spectra from Mercury," says Izenberg. "The infrared continues to show very little spectral variation indicative of distinct mineralogies, and we are working hard to tease out what we can."
An important chapter of the story, however, appears to be at ultraviolet wavelengths, he says. "Iron in rocks also has effects in this region of the spectrum as well, but those effects are less well studied and understood. However it is here that we see variations among, for example, fresh-looking craters, plains, hollows, pyroclastic deposits, and low-reflectance units."
According to Izenberg, the variations in the ultraviolet may reflect both iron content and the type of rocks that hold it and may provide hints at other materials, such as sulfur, which have characteristic ultraviolet reflectance signatures as well. "Evidence from other instruments on MESSENGER, such as the X-Ray Spectrometer, corroborates low iron abundance near the surface and the presence of sulfur, so as our analyses advance we'll be working to correlate the findings across all instruments."
Looking Ahead
MESSENGER continues to send back data that illuminate Mercury's mysteries. The knowledge gained is already sharpening the mission goals of the dual-spacecraft BepiColombo mission, scheduled to launch to Mercury in 2014. Members of the MESSENGER team met with BepiColombo scientists at Kyoto University in Japan last month to review the state of knowledge about Mercury and to present initial MESSENGER orbital results.
"We discussed many of the new findings that will be covered in the MESSENGER sessions today," says MESSENGER Project Scientist Ralph McNutt. "BepiColombo team members presented new perspectives on surface mineralogy from recent high-temperature laboratory measurements and new theories for Mercury's formation and for the generation of Mercury's magnetic field. This meeting continued a dialogue, begun more than a decade ago, on the synergies of the two investigations and how ongoing MESSENGER measurements are informing the planning for BepiColombo operations."
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and entered orbit about Mercury on March 17, 2011 (March 18, 2011 UTC), to begin a yearlong study of its target planet. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
Orbital Observations of Mercury Reveal Flood Lavas, Hollows, and Unprecedented Surface Details - September 29, 2011
After only six months in orbit around Mercury, NASA's MESSENGER spacecraft is sending back information that has revolutionized the way scientists think about the innermost planet. Analyses of new data from the spacecraft show, among other things, new evidence that flood volcanism has been widespread on Mercury, the first close-up views of Mercury's "hollows," the first direct measurements of the chemical composition of Mercury's surface, and the first global inventory of plasma ions within Mercury's space environment.
The results are reported in a set of seven papers published in a special section of Science magazine on September 30, 2011.
"MESSENGER's instruments are capturing data that can be obtained only from orbit," says MESSENGER Principal Investigator Sean Solomon, of the Carnegie Institution of Washington. "We have imaged many areas of the surface at unprecedented resolution, we have viewed the polar regions clearly for the first time, we have built up global coverage with our images and other data sets, we are mapping the elemental composition of Mercury's surface, we are conducting a continuous inventory of the planet's neutral and ionized exosphere, and we are sorting out the geometry of Mercury's magnetic field and magnetosphere. And we've only just begun. Mercury has many more surprises in store for us as our mission progresses."
MESSENGER Reveals Flood Volcanism
For decades scientists had puzzled over whether Mercury had volcanic deposits on its surface. MESSENGER's three flybys answered that question in the affirmative, but the global distribution of volcanic materials was not well constrained. New data from orbit show a huge expanse of volcanic plains surrounding the north polar region of Mercury. These continuous smooth plains cover more than 6% of the total surface of Mercury.
The volcanic deposits are thick. "Analysis of the size of buried 'ghost' craters in these deposits shows that the lavas are locally as thick as 2 kilometers" (or 1.2 miles), explains James Head of Brown University, the lead author of one of the Science reports. "If you imagine standing at the base of the Washington Monument, the top of the lavas would be something like 12 Washington Monuments above you."
According to Head, the deposits appear typical of flood lavas, huge volumes of solidified molten rock similar to those found in the few-million-year-old Columbia River Basalt Group, which at one point covered 150,000 square kilometers (60,000 square miles) in the northwest United States. "Those on Mercury appear to have poured out from long, linear vents and covered the surrounding areas, flooding them to great depths and burying their source vents," Head says.
Scientists have also discovered vents, measuring up to 25 kilometers (16 miles) in length, that appear to be the source of some of the tremendous volumes of very hot lava that have rushed out over the surface of Mercury and eroded the substrate, carving valleys and creating teardrop-shaped ridges in the underlying terrain. "These amazing landforms and deposits may be related to the types of unusual compositions, similar to terrestrial rocks called komatiites, being seen by other instruments and reported in this same issue of Science," Head says. "What's more, such lavas may have been typical of an early period in Earth's history, one for which only spotty evidence remains today."
As MESSENGER continues to orbit Mercury, the imaging team is building up a global catalog of these volcanic deposits and is working with other instrument teams to construct a comprehensive view of the history of volcanism on Mercury.
Hollows on Mercury
Images collected by MESSENGER have revealed an unexpected class of landform on Mercury and suggest that a previously unrecognized geological process is responsible for its formation. Images collected during the Mariner 10 and MESSENGER flybys of Mercury showed that the floors and central mountain peaks of some impact craters are very bright and have a blue color relative to other areas of Mercury. These deposits were considered to be unusual because no craters with similar characteristics are found on the Moon. But without higher-resolution images, the bright crater deposits remained a curiosity.
Now MESSENGER's orbital mission has provided close-up, targeted views of many of these craters.
"To the surprise of the science team, it turns out that the bright areas are composed of small, shallow, irregularly shaped depressions that are often found in clusters," says David Blewett, a staff scientist at the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Md., and lead author of one of the Science reports. "The science team adopted the term 'hollows' for these features to distinguish them from other types of pits seen on Mercury."
Hollows have been found over a wide range of latitudes and longitudes, suggesting that they are fairly common across Mercury. Many of the depressions have bright interiors and halos, and Blewett says the ones detected so far have a fresh appearance and have not accumulated small impact craters, indicating that they are relatively young.
"Analysis of the images and estimates of the rate at which the hollows may be growing led to the conclusion that they could be actively forming today," Blewett says. "The old conventional wisdom was that 'Mercury is just like the Moon.' But from its vantage point in orbit, MESSENGER is showing us that Mercury is radically different from the Moon in just about every way we can measure."
Mercury's Surface and Exospheric Composition, Up Close and Personal
Scientists are collecting data about the chemical composition of Mercury's surface that could not have been obtained without the sustained observing perspective that MESSENGER's orbit provides, and that information is being used to test models of Mercury's formation and shed light on the dynamics of the planet's exosphere.
Measurements of Mercury's surface by MESSENGER's Gamma-Ray Spectrometer (GRS) reveal a higher abundance of the radioactive element potassium, a moderately volatile element that vaporizes at a relatively low temperature, than previously predicted. Together with MESSENGER's X-Ray Spectrometer (XRS), it also shows that Mercury has an average surface composition different from those of the Moon and other terrestrial planets.
"Measurements of the ratio of potassium to thorium, another radioactive element, along with the abundance of sulfur detected by XRS, indicate that Mercury has a volatile inventory similar to Venus, Earth, and Mars, and much larger than that of the Moon," says APL Staff Scientist Patrick Peplowski, lead author of one of the Science papers.
These new data rule out most existing models for Mercury's formation that had been developed to explain the unusually high density of the innermost planet, which has a much higher mass fraction of iron metal than Venus, Earth, or Mars, Peplowski pointed out. Overall, Mercury's surface composition is similar to that expected if the planet's bulk composition is broadly similar to that of highly reduced or metal-rich chondritic meteorites (material that is left over from the formation of the solar system).
MESSENGER has also collected the first global observations of plasma ions in Mercury's magnetosphere. Over 65 days covering more than 120 orbits, MESSENGER's Fast Imaging Plasma Spectrometer (FIPS) made the first long-term measurements of Mercury's ionized exosphere.
The team found that sodium is the most important ion contributed by the planet. "We had previously observed neutral sodium from ground observations, but up close we've discovered that charged sodium particles are concentrated near Mercury's polar regions where they are likely liberated by solar wind ion sputtering, effectively knocking sodium atoms off Mercury's surface," notes the University of Michigan's Thomas Zurbuchen, author of one of the Science reports. "We were able to observe the formation process of these ions, one that is comparable to the manner by which auroras are generated in the Earth atmosphere near polar regions."
The FIPS sensor detected helium ions throughout the entire volume of Mercury's magnetosphere. "Helium must be generated through surface interactions with the solar wind," says Zurbuchen. "We surmise that the helium was delivered from the Sun by the solar wind, implanted on the surface of Mercury, and then fanned out in all directions.
"Our results tell us is that Mercury's weak magnetosphere provides the planet very little protection from the solar wind," he continued. "Extreme space weather must be a continuing activity at the surface of the planet closest to the Sun."
"These revelations emphasize that Mercury is a fascinating world that is unmatched in the solar system," says Blewett. "We have barely begun to understand what Mercury is really like and are eager to discover what Mercury can tell us about the processes that led to formation of the planets as we see them today."
NASA hosted a media teleconference at 2 p.m. EDT on Thursday, Sept. 29, to discuss the new data and images. Related images and supporting briefing information is available at Press-Conferences.html#20110929.
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and entered orbit about Mercury on March 17, 2011 (March 18, 2011 UTC), to begin a yearlong study of its target planet. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
MESSENGER Reveals New Details of Planet Mercury - September 27, 2011
NASA will host a media teleconference at 2 p.m. EDT on Thursday, September 29, to discuss new data and images from the first spacecraft to orbit Mercury. The new findings are reported in a series of seven papers published in a special section of Science magazine on September 30.
NASA's MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft conducted fifteen laps through the inner solar system for more than six years before achieving the historic orbit insertion on March 18.
Briefing participants are:
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and entered orbit about Mercury on March 17, 2011 (March 18, 2011 UTC), to begin a yearlong study of its target planet. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
MESSENGER Team Delivers First Orbital Data to Planetary Data System - September 8, 2011
Data collected during MESSENGER's first two months in orbit around Mercury have been released to the public by the Planetary Data System (PDS), an organization that archives and distributes all of NASA's planetary mission data. Calibrated data from all seven of MESSENGER's science instruments, plus radio science data from the spacecraft telecommunications system, are included in this release.
"It's a real milestone for the first data ever obtained from orbit around Mercury to be available now in the PDS," says Nancy Chabot, Instrument Scientist for MESSENGER's Mercury Dual Imaging System (MDIS).
"Scientists around the world will use these data to better understand Mercury and the formation and evolution of our solar system as a whole," says Chabot, of the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Md. "However, to me, one of the most exciting aspects of this release is that these data now in the PDS are just the first of much more to come. MESSENGER continues to send us new data practically every day!"
The science results from these instruments have already shed light on questions about Mercury that have lingered for more than three decades. Many of these results were highlighted in a June 16 press conference at NASA headquarters.
For instance, says MESSENGER Project Scientist Ralph McNutt of APL, "The imaging has highlighted the importance of volcanism in plains formation in the planet's history, and the geochemical remote sensing instruments are providing new insights into formation scenarios for the planet. Geophysics data are yielding new information on Mercury's internal structure, and data from the exosphere and magnetosphere instruments are giving us the first continuous view of Mercury's interaction with its local space environment.
"The availability of these data via PDS will allow scientists around the world to study the data and begin making even more connections and discoveries," McNutt adds.
Since the mid-1990s, NASA has required all of its planetary missions to archive data in the PDS, an active archive that makes available well-documented, peer-reviewed data to the research community. The PDS includes eight university/research center science teams, called discipline nodes, each of which specializes in a specific area of planetary data. The contributions from these nodes provide a data-rich source for scientists, researchers, and developers.
"PDS deliveries are the result of a concerted effort between the MESSENGER team and the PDS that starts well before the release to the public," says APL's Susan Ensor, MESSENGER's Science Operations Center lead. "Approximately 50 MESSENGER team members were actively involved in making this PDS delivery, including instrument team members, developers from Applied Coherent Technology Corporation, and Science Operations Center personnel."
Previous MESSENGER PDS deliveries included data from cruise and flybys of the Earth, Venus, and Mercury. All of the MESSENGER data archived at the PDS thus far are available at http://pds.nasa.gov. As of this release, MESSENGER will have delivered 1.1 terabytes of raw and calibrated data to the PDS, including more than 30,000 images (of which over 18,000 are from orbit).
The team will submit three more PDS deliveries at six-month intervals from MESSENGER's primary mission. "Improved calibrations will be incorporated in these future deliveries," Ensor says. "Advanced products, including Mercury maps, will be included in the final primary mission delivery in March 2013."
The MESSENGER team has created an innovative software tool with which the public can view data from this delivery. ACT-REACT-Quick Map provides a simple, interactive Web interface to MESSENGER data. Developed by Applied Coherent Technology Corporation, Quick Map allows users to examine global mosaics constructed with high-resolution images from this PDS delivery.
The tool also provides weekly updates of coverage for surface-observing instruments, as well as the status of specially targeted MDIS observations. Information is also available that can be used to locate MESSENGER data products at the PDS. QuickMap can be accessed via links on each of the MESSENGER websites at http://messenger.jhuapl.edu/ and http://www.nasa.gov/messenger.
"The MESSENGER team is delighted to share the orbital observations of Mercury with the planetary science community and the public," adds MESSENGER Principal Investigator Sean Solomon, of the Carnegie Institution of Washington. "The first global exploration of our solar system's innermost planet is a wonderful adventure, and there are plenty of front-row seats for all to participate."
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and entered orbit about Mercury on March 17, 2011 (March 18, 2011 UTC), to begin a yearlong study of its target planet. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
MESSENGER Navigates Second Hot Season, Executes Third Orbit-Correction Maneuver - September 7, 2011
Today the MESSENGER spacecraft emerged unscathed from the second of four "hot seasons" expected to occur during its one-year primary mission in orbit around Mercury. Hours later, mission controllers at the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Md., successfully executed a maneuver to adjust the spacecraft's trajectory.
"Operating MESSENGER in Mercury orbit is a bit like driving a high-performance automobile on a challenging track with continuously varying road conditions and unpredictable changes in weather," says MESSENGER Principal Investigator Sean Solomon, of the Carnegie Institution of Washington. "Our road track is three-dimensional, our environment imposes extreme variations in temperature every 12 hours, and our weather comes from space. Nonetheless, our spacecraft is resilient, our operations team is experienced at handling all the needed maneuvers, and we're continuing to learn how to squeeze as much science as possible from our orbital observations."
This hot season began on August 9 and lasted nearly one month. During that time, the closest approach of the spacecraft to Mercury was on the sunlit side of the planet. MESSENGER's sunshade reached temperatures as high as 350°C during this season, and its solar panels had to be turned off the Sun for short periods during each orbit to protect them from overheating.
Within this second hot season there was a period — from August 20 to August 29 — in which the spacecraft experienced an eclipse during the portion of each orbit when it passed through the shadow of the planet. For eclipses that last longer than 35 minutes, the probe's battery cannot power the full science payload, and some instruments must be turned off for a brief period.
Even with the challenges of operating the satellite in these extreme orbital environments, the team was able to fine-tune the system to increase the scientific data return from Mercury, says MESSENGER Systems Engineer Eric Finnegan, of APL.
"We went into the first hot season with very conservative assumptions for the spacecraft's response to the Mercury environment," says Finnegan. "To conserve energy, only one of MESSENGER's seven instruments was allowed to operate continuously throughout that season. As it turned out, the battery performed superbly, and there was sufficient energy margin to allow two additional instruments to maintain continuous measurements throughout the entire eclipse season." In addition to the Gamma-Ray Spectrometer, the Neutron Spectrometer and the Magnetometer remained on continuously through the second hot season.
Having weathered the hot season, MESSENGER engineers immediately turned to the task of adjusting the spacecraft's orbit around Mercury. This third of five expected orbit-correction maneuvers lowered the periapsis altitude from about 470 kilometers back to 200 kilometers.
"MESSENGER's orbit is continuously changing, so correction maneuvers are scheduled throughout the year to ensure that the orbital parameters remain within the desired ranges for the planned science observations," says MESSENGER Project Manager Peter Bedini. "This was the second time that the periapsis altitude — the closest approach of the spacecraft to the planet — has been reset to 200 kilometers. One more such correction is planned for the primary mission, and that event is presently scheduled to take place in early December."
The 2-minute, 46-second engine burn began at 15:08 UTC (11:08 a.m. EDT) and reduced the period of the spacecraft's orbit around the innermost planet from 12 hours to 11 hours 46 minutes. The next orbit-correction maneuver, designed to restore the orbital period to 12 hours, is scheduled for October 24.
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and entered orbit about Mercury on March 17, 2011 (March 18, 2011 UTC), to begin a yearlong study of its target planet. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
MESSENGER Co-Investigator Louise Prockter has been elected a fellow of the Geological Society of America (GSA). Established in 1888, the GSA — comprised of about 25,000 members — seeks to foster the quest for understanding the Earth, planets, and life; catalyze new scientific ways of thinking about natural systems; and support the application of geoscience knowledge and insight to human needs, aspirations, and Earth stewardship.
To become a fellow, an honor reserved for less than 3 percent of the national society's members, honorees must be nominated by an existing GSA fellow in recognition of distinguished contributions to the geosciences and approved by the entire GSA senate.
Prockter "is deserving of this recognition because of her high standing in the scientific community, contributions to major spacecraft missions, the significance of her planetary geology research, her leadership of scientific teams, and her service through editorships, peer review panels, and as a GSA officer in the Planetary Geology Division," wrote NASA Geophysicist Herbert V. Frey, in the nomination letter he submitted.
Prockter is the supervisor of the Space Department's Planetary Exploration Group at the Johns Hopkins University Applied Physics Laboratory in Laurel, Md. As MESSENGER Deputy Project Scientist, she helps ensure that the mission will meet or exceed its scientific objectives. She earlier served as Instrument Scientist for the mission's Mercury Dual Imaging System. Her experience also includes work on the Near Earth Asteroid Rendezvous and Galileo missions.
She will be recognized as a GSA fellow at the national meeting of the society to be held in Minneapolis in October. Read more about Prockter here.
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and entered orbit about Mercury on March 17, 2011 (March 18, 2011 UTC), to begin a yearlong study of its target planet. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
MESSENGER Marks Seventh Anniversary of Launch - August 3, 2011
Seven years ago, on August 3, 2004, MESSENGER left Earth aboard a three-stage Boeing Delta II rocket to begin a journey that would take it more than 15 laps through the solar system, through six planetary flybys, and ultimately into orbit around Mercury. The spacecraft has travelled 5.247 billion miles (8.445 billion kilometers) relative to the Sun, and the team is one-third of the way through the one-year science campaign to understand the innermost planet.
"As exciting as it was at the time, MESSENGER's launch seems a long time ago," says MESSENGER Principal Investigator Sean Solomon, of the Carnegie Institution of Washington. "Our spacecraft is now in the prime of its life, enjoying a year of sustained excitement as spectacular new observations of Mercury are acquired and sent to Earth every day."
As of July 30, the team has been taking observations of the planet's surface for two Mercury sidereal days. Sidereal time is a time-keeping system astronomers use to keep track of the direction to point their telescopes to view a given star in the night sky. One full rotation of Mercury about its spin axis relative to the distant stars is a sidereal day, about 59 Earth days.
"This is certainly a great milestone for us, since the spacecraft has now experienced every thermal and solar eclipse season at least once," says Mission Operations Manager Andy Calloway. "But we're really looking forward to one complete Mercury solar day. This milestone will be achieved after three full Mercury rotations relative to the stars, but more importantly it will reset the clock for Mercury's rotation relative to the Sun and is one-half of our primary mission phase."
MESSENGER's primary mission is divided into two Mercury solar days, so that lighting conditions can be repeated for filling gaps in imaging, targeted observations can be optimized, and stereo imaging can be accomplished. Mercury is the only planet in the solar system with three rotations for every two trips around the Sun. Mercury's day and year were once thought to have the same length, which would mean that Mercury would keep the same face to the Sun much as the Moon does to Earth, until radar observations in 1965 confirmed the 3:2 resonance.
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and entered orbit about Mercury on March 18, 2011, to begin a one-year study of its target planet. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
MESSENGER Makes Another Successful Orbit Adjustment - July 27, 2011
The MESSENGER spacecraft continued to fine-tune its orbit around Mercury yesterday afternoon when mission controllers at the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Md., successfully executed the second orbit-correction maneuver of the mission.
The 3-minute, 8-second engine burn stretched the spacecraft's orbit around the innermost planet from 11 hours 48 minutes to a precise 12 hours. This second of an expected five maneuvers planned for the mission's primary orbital phase began at 5:20 P.M. EDT, and used approximately 1.9 kilograms of fuel.
"MESSENGER's first orbit-correction maneuver, which took place in June, reset the periapsis altitude of the orbit to 200 kilometers, but also shortened the orbital period. This second maneuver has reset the period to its nominal value of 12 hours," says APL's Peter Bedini, MESSENGER project manager.
MESSENGER Mission Systems Engineer Eric Finnegan, of APL, said the engine burn was "on target and a sweet success. We're precisely where we need to be to continue to capture amazing data from Mercury's surface." The next orbit-correction maneuver is scheduled for September 7 and will lower the periapsis altitude from about 470 kilometers back to 200 kilometers.
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and entered orbit about Mercury on March 17, 2011 (March 18, 2011 UTC), to begin a yearlong study of its target planet. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
The Mid-Atlantic Section of the American Institute of Aeronautics and Astronautics (AIAA) has named MESSENGER team members Peter Bedini and Eric Finnegan as Engineering Manager of the Year and Engineer of the Year, respectively, for 2011. Bedini and Finnegan, both of the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Md., will be honored at an awards dinner later this month.
Bedini is the MESSENGER Project Manager. In that role he oversees all aspects of the mission, including spacecraft engineering activities; coordination with the mission science leads, the Principal Investigator, and NASA management; delivery of data to the Planetary Data System; and operation of the spacecraft during its cruise to and orbit around Mercury.
The past year presented many special management challenges as the spacecraft entered its final year of cruise operations and as the MESSENGER team prepared for the orbital phase of the mission through a series of flight tests, operational rehearsals, and readiness reviews.
Bedini is credited with "skillfully and artfully" managing these activities, which culminated in a successful Mercury orbit insertion on March 18, 2011, making MESSENGER the first spacecraft ever to orbit the solar system's innermost planet.
Finnegan is the MESSENGER Mission Systems Engineer. According to AIAA, Finnegan "demonstrated outstanding multi-disciplinary technical ability, leadership, and the ability to remain calmly focused on the 'big picture' on one of the most complex planetary missions that APL has undertaken."
He is credited with establishing the overall operational requirements for mission execution during the cruise and on-orbit phases of the MESSENGER mission, and with leading the team of engineers and scientists through the design, review, and execution of all spacecraft mission events.
Finnegan supervised the MESSENGER team through the successful completion of four planetary flybys, four large-scale deep-space maneuvers, and the critical orbit insertion burn on March 18, 2011. In 2010, during the final year of the more than six-year cruise, he developed an overall plan for the verification of the on-orbit operations of the spacecraft and led his team through an extensive set of preparation, analysis, independent review, and testing activities. At the conclusion of these exercises, he and his team had demonstrated 10 simulated weeks of on-orbit operations and executed, via computer simulation, all 52 weeks of spacecraft and instrument commanding, providing high-fidelity verification of the tools and procedures that are currently being used by the MESSENGER spacecraft at Mercury.
"For more than four years, Peter and Eric have overseen, respectively, the MESSENGER project and its engineering team," says MESSENGER Principal Investigator Sean Solomon, of the Carnegie Institution of Washington. "Throughout that time, each of them has demonstrated an extraordinarily high level of professional dedication, exceptional attention to all aspects of the mission, and outstanding skill at managing a large team. That there is now and for the first time a spacecraft operating successfully in orbit about Mercury is in no small part the result of the sustained efforts of these two superbly skilled leaders."
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and entered orbit about Mercury on March 18, 2011, to begin a one-year study of its target planet. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
MESSENGER Co-Investigator Scott Murchie, of the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Md., will be awarded the NASA Distinguished Public Service Medal, the highest honor that NASA bestows to an individual working outside the government. The award is granted only to individuals whose singular accomplishments contributed substantially to the NASA mission.
Murchie is receiving the honor in recognition of his leadership of the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) investigation. CRISM, flying aboard the Mars Reconnaissance Orbiter (MRO), is one of NASA's high-technology instruments designed to seek traces of past and present water on the Martian surface.
Murchie is also accepting two NASA Public Service Group Achievment Awards on behalf of the MRO CRISM Team: one for developing and operating the CRISM instrument and processing and distributing the data, and one for analyzing the data and publishing the results, thus advancing the understanding of the Martian surface, its composition, and its evolution.
MESSENGER Co-Investigator Maria Zuber, of the Massachusetts Institute of Technology, will also receive a Group Achievement Award on behalf of the MRO Gravity Science Team for conducting the gravity science investigation, calculating static and time-varying gravity fields, and providing constraints on interior processes and volatile transport.
Murchie will receive the Public Service award during a ceremony at NASA Headquarters in Washington, D.C., on June 30, 2011; the Group Achievement awards will be presented July 19, 2011 at NASA's Jet Propulsion Laboratory in Pasadena, Calif.
"I'm incredibly flattered by this honor from NASA, which is really an acknowledgement of the fine team of people I work with, on CRISM and also on MESSENGER and a decade ago on NEAR," Murchie said. "APL has a great team mentality, and it's an honor to be part of that."
Murchie studies the surface composition of Mars, asteroids, and the Moon using imaging and spectroscopy. He participated in the development of MESSENGER's Mercury Dual Imaging System (MDIS) and contributes to the mission imaging strategy, and he is participating in the analysis of MDIS and Mercury Atmospheric and Surface Composition Spectrometer spectral measurements of Mercury's surface.
"The MESSENGER Science Team is extremely fortunate to include individuals such as Scott and Maria who have led and continue to direct scientific investigations on other spacecraft missions," added MESSENGER Principal Investigator Sean Solomon, of the Carnegie Institution of Washington. "Their experience on MRO and other missions ensures that the scientific return from MESSENGER will substantially advance our understanding not only of Mercury but of all the inner planets."
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and entered orbit about Mercury on March 18, 2011, to begin a one-year study of its target planet. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
After nearly three months in orbit about Mercury, MESSENGER's payload is providing a wealth of new information about the planet closest to the Sun, as well as a few surprises.
The spacecraft entered orbit around Mercury on March 18, 2011, becoming the first spacecraft ever to do so. Its instruments are performing the first complete reconnaissance of the planet's geochemistry, geophysics, geologic history, atmosphere, magnetosphere, and plasma environment.
Tens of thousands of images of major features on the planet — previously seen only at comparatively low resolution — are now available in sharp focus. Measurements of the chemical composition of Mercury's surface are providing important clues to the origin of the planet and its geological history. Maps of the planet's topography and magnetic field are revealing new clues to Mercury's interior dynamical processes. And scientists now know that bursts of energetic particles in Mercury's magnetosphere are a continuing product of the interaction of Mercury's magnetic field with the solar wind.
"MESSENGER has passed a number of milestones just this week," offers MESSENGER principal investigator Sean Solomon of the Carnegie Institution of Washington. "We completed our first perihelion passage from orbit on Sunday, our first Mercury year in orbit on Monday, our first superior solar conjunction from orbit on Tuesday, and our first orbit-correction maneuver on Wednesday. Those milestones provide important context to the continuing feast of new observations that MESSENGER has been sending home on nearly a daily basis."
A Surface Revealed in Unprecedented Detail
As part of MESSENGER's global imaging campaign, the Mercury Dual Imaging System (MDIS) is acquiring global monochrome and stereo base maps with an average resolution of 250 meters per pixel and a global color base map at an average of 1.2 kilometer per pixel. These base maps are providing the first global look at the planet under optimal viewing conditions.
Orbital images reveal broad expanses of smooth plains near Mercury's north pole. Flyby images from MESSENGER and from Mariner 10 in the 1970s indicated that smooth plains may be important near the north pole, but much of the territory was viewed at unfavorable imaging conditions.
MESSENGER's new orbital images show that the plains are likely among the largest expanses of volcanic deposits on Mercury, with thicknesses of up to several kilometers. The broad expanses of plains confirm that volcanism shaped much of Mercury's crust and continued through much of Mercury's history, despite an overall contractional stress state that tended to inhibit the extrusion of volcanic material onto the surface.
Among the fascinating features seen in flyby images of Mercury were bright, patchy deposits on some crater floors. Without high-resolution images to obtain a closer look, these features remained only a curiosity. New targeted MDIS observations at up to 10 meters per pixel reveal these patchy deposits to be clusters of rimless, irregular pits varying in size from hundreds of meters to several kilometers. These pits are often surrounded by diffuse halos of higher-reflectance material, and they are found associated with central peaks, peak rings, and rims of craters.
"The etched appearance of these landforms is unlike anything we've seen before on Mercury or the Moon," says Brett Denevi, a staff scientist at the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Md., and a member of the MESSENGER imaging team. "We are still debating their origin, but they appear to have a relatively young age and may suggest a more abundant than expected volatile component in Mercury's crust."
Mercury's Surface Composition
The X-Ray Spectrometer (XRS) — one of two instruments on MESSENGER designed to measure the abundances of many key elements on Mercury — has made several important discoveries since the orbital mission began. The magnesium/silicon, aluminum/silicon, and calcium/silicon ratios averaged over large areas of the planet's surface show that, unlike the surface of the Moon, Mercury's surface is not dominated by feldspar-rich rocks.
XRS observations have also revealed substantial amounts of sulfur at Mercury's surface, lending support to prior suggestions from ground-based telescopic spectral observations that sulfide minerals are present. This discovery suggests that the original building blocks from which Mercury was assembled may have been less oxidized than those that formed the other terrestrial planets, and it has potentially important implications for understanding the nature of volcanism on Mercury.
MESSENGER's Gamma-Ray and Neutron Spectrometer has detected the decay of radioactive isotopes of potassium and thorium and has allowed a determination of the bulk abundances of these elements. "The abundance of potassium rules out some prior theories for Mercury's composition and origin," says Larry Nittler, a staff scientist at the Carnegie Institution of Washington. "Moreover, the inferred ratio of potassium to thorium is similar to that of other terrestrial planets, suggesting that Mercury is not highly depleted in volatiles, contrary to some prior ideas about its origin."
Mapping of Mercury's Topography and Magnetic Field
MESSENGER's Mercury Laser Altimeter has been systematically mapping the topography of Mercury's northern hemisphere. After more than two million laser-ranging observations, the planet's large-scale shape and profiles of geological features are both being revealed in high detail. The north polar region of Mercury, for instance, is a broad area of low elevations.
The overall range in topographic heights seen to date exceeds 9 kilometers.
Two decades ago, Earth-based radar images showed that near both Mercury's north and south poles are deposits characterized by high radar backscatter. These polar deposits are thought to consist of water ice and perhaps other ices preserved on the cold, permanently shadowed floors of high-latitude impact craters. MESSENGER's altimeter is testing this idea by measuring the floor depths of craters near Mercury's north pole. To date, the depths of craters hosting polar deposits are consistent with the idea that those deposits occupy areas in permanent shadow.
The geometry of Mercury's internal magnetic field can potentially discriminate among theories for how the field is generated. An important finding is that Mercury's magnetic equator, determined on successive orbits as the point where the direction of the internal magnetic field is parallel to the spin axis of the planet, is well north of the planet's geographic equator. The best-fitting internal dipole magnetic field is located about 0.2 Mercury radii, or 480 km, northward of the planet's center. The dynamo mechanism in Mercury's molten, metallic outer core responsible for generating the planet's magnetic field therefore has a strong north-south asymmetry.
As a result of this north-south asymmetry, the geometry of magnetic field lines is different in Mercury's north and south polar regions. In particular, the magnetic "polar cap" where field lines are open to the interplanetary medium is much larger near the south pole. This geometry implies that the south polar region is much more exposed than in the north to charged particles heated and accelerated by solar wind–magnetosphere interactions. The impact of those charged particles onto Mercury's surface contributes both to the generation of the planet's tenuous atmosphere and to the "space weathering" of surface materials, both of which should have a north-south asymmetry given the different magnetic field configurations at the two poles.
Energetic Particle Events at Mercury
One of the major discoveries made by Mariner 10 during the first of its three flybys of Mercury in 1974 were bursts of energetic particles in Mercury's Earth-like magnetosphere. Four bursts of particles were observed on that flyby, so it was puzzling that no such strong events were detected by MESSENGER during any of its three flybys of the planet in 2008 and 2009.
With MESSENGER now in near-polar orbit about Mercury, energetic events are being seen almost like clockwork, says MESSENGER Project Scientist Ralph McNutt, of APL. "While varying in strength and distribution, bursts of energetic electrons — with energies from 10 kiloelectron volts (keV) to more than 200 keV — have been seen in most orbits since orbit insertion," McNutt says. "The Energetic Particle Spectrometer has shown these events to be electrons rather than energetic ions, and to occur at moderate latitudes. The latitudinal location is entirely consistent with the events seen by Mariner 10."
With Mercury's smaller magnetosphere and with the lack of a substantial atmosphere, both the generation of these energetic electrons and their distribution are different than at Earth. One candidate mechanism for the generation of these energetic electrons is the formation of a "double layer," a plasma structure with large electric fields along the local magnetic field. Another is induction brought about by rapid changes in the magnetic field, a process that follows the principle used in generators on Earth to produce electric power. Which of these mechanisms, if either, predominates in the acceleration of energetic electrons will be the subject of study over the coming months.
"One mystery has been answered, only to be replaced by another, but that is how science works," McNutt says. "In the coming months as MESSENGER's orbit swings around the planet, we will be able to observe the overall geometry of these events, providing yet more clues to their production and interaction with the planet."
"We are assembling a global overview of the nature and workings of Mercury for the first time," adds Solomon, "and many of our earlier ideas are being cast aside as new observations lead to new insights. Our primary mission has another three more Mercury years to run, and we can expect further surprises as our solar system's innermost planet reveals its long-held secrets."
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and entered orbit about Mercury on March 18, 2011, to begin a one-year study of its target planet. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
MESSENGER Adjusts Its Orbit around Mercury - June 15, 2011
The MESSENGER spacecraft successfully completed its first orbit-correction maneuver today to reset its periapsis altitude — the lowest point of MESSENGER's orbit about Mercury relative to the planet's surface — from 506 kilometers to approximately 200 kilometers.
MESSENGER was 198 million kilometers (123 million miles) from Earth when the maneuver began at 3:40 p.m. EDT. Mission controllers at The Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Md., verified the start of the maneuver about 10 minutes, 58 seconds later, when the first signals indicating spacecraft thruster activity reached NASA's Deep Space Network tracking station outside Goldstone, California.
This is the first of five maneuvers planned for the primary orbital phase of the mission to keep orbital parameters within desired ranges for optimal science observations. The spacecraft's main rocket engine fired for only 15 seconds of the total maneuver duration of 2 minutes and 52 seconds. MESSENGER's orbital velocity was changed by a total of 28 m/s to make the corrections essential for continuing the planned measurement campaigns.
"The orbit that the spacecraft follows around the planet slowly changes as time goes by," explained APL's James Hudson, lead guidance and control engineer for the MESSENGER mission operations team. "Because of Mercury's proximity to the Sun and MESSENGER's highly eccentric orbit, solar gravity has a strong effect on the spacecraft's orbit, particularly periapsis altitude."
MESSENGER Mission Systems Engineer Eric Finnegan, of APL, said that the team was well prepared for the maneuver and everything proceeded as expected. "Initial data from the burn indicate nominal maneuver execution. MESSENGER's orbital trajectory around Mercury has now been reset to continue our in-depth exploration of the innermost planet."
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and entered orbit about Mercury on March 18, 2011, to begin a one-year study of its target planet. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
MESSENGER Endures Its First Hot Season - June 13, 2011
Yesterday the MESSENGER spacecraft successfully completed the first of four "hot seasons" expected to occur during its one-year primary mission in orbit about Mercury. During these hot seasons, the Sun-facing side of the probe's sunshade can reach temperatures as high as 350°C.
These hot conditions are the result of two concurrent circumstances, says MESSENGER Mission Systems Engineer Eric Finnegan, of the Johns Hopkins University Applied Physics Laboratory in Laurel, Md. "Mercury is in an eccentric orbit, and its distance from the Sun varies over 88 days, from 43,689,229 miles to 28,816,300 miles," he explains. "On May 13, Mercury began heading closer to the Sun in its orbit. The planet reached its closest distance from the Sun on June 12."
The second contributor to this heat is the geometry of MESSENGER's orbit relative to the hot dayside of Mercury. The spacecraft is in a highly eccentric orbit around the planet, approaching to within 310 miles of the surface every 12 hours.
"During this hot period, the closest point of approach of the spacecraft to Mercury's surface occurs on the sunlit side of the planet, so for almost one hour per orbit the spacecraft must pass between the Sun on one side and the hot dayside surface of the planet on the other," Finnegan says. "To add further extremes, this season is also when the spacecraft passes over the nightside of the planet at high elevations and experiences the longest solar eclipses of the mission. During this period, when eclipses last as long as 62 minutes per orbit, the solar arrays are not illuminated and the spacecraft must derive its power from its internal battery."
High temperatures are always a risk to mechanical and electronic systems, and the geometry of this portion of the orbit severely constrains the ability of the spacecraft to cool itself by radiating heat to cold space. MESSENGER engineers have taken several steps to ensure that the spacecraft remains safe.
"We rotated the solar arrays off the Sun through some of the hottest points so they do not have a view to either the Sun or the hot, dayside surface of the planet," Finnegan says. "We are power cycling some of the more sensitive instruments to reduce their internal heat dissipation. In a manner similar to the treatment of the solar arrays, we are also adjusting the attitude of the spacecraft to keep some of the more sensitive parts of the spacecraft from seeing the hottest parts of the planet's surface."
All of the instruments have been operating during this period. Finnegan says that there have been times during each orbit when instruments are turned off, however, mostly to conserve power during eclipses.
These conditions are expected to recur approximately every 88 days (i.e., the time it takes Mercury to orbit the Sun). MESSENGER can therefore look forward to three more hot seasons during the course of its primary mission.
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and entered orbit about Mercury on March 17, 2011 (March 18, 2011 UTC), to begin a yearlong study of its target planet. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
NASA Releasing New Spacecraft Orbital Views of Mercury - June 10, 2011
NASA will host a news conference at 1 p.m. EDT on Thursday, June 16, 2011, to reveal new images and science findings from the first spacecraft to orbit Mercury. The event will be held in the NASA Headquarters auditorium located at 300 E St. SW, in Washington. NASA Television and the agency's website will broadcast the event.
NASA's MErcury Surface, Space ENvironment, GEochemistry, and Ranging, or MESSENGER spacecraft conducted more than a dozen laps through the inner solar system for six years prior to achieving the historic orbit insertion on March 17, 2011 (EDT).
Briefing participants are:
-- Brett Denevi, scientist, Johns Hopkins University Applied Physics Laboratory (APL), Laurel, Md.
-- Ralph McNutt, Jr., MESSENGER project scientist, APL
-- Larry Nittler, scientist, Department of Terrestrial Magnetism, Carnegie Institution of Washington
-- Sean Solomon, MESSENGER principal investigator, Carnegie Institution
Reporters may attend the event, ask questions from participating NASA locations, or join by phone. To obtain dial-in information, journalists must email Dwayne Brown at dwayne.c.brown@nasa.gov with their name, media affiliation and work telephone number by 9 a.m. on June 16, 2011.
For more information about the mission, visit:
http://www.nasa.gov/mission_pages/messenger/main/index.html
For NASA TV streaming video, downlink and schedule information, visit:
http://www.nasa.gov/ntv
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and entered orbit about Mercury on March 17, 2011 (March 18, 2011 UTC), to begin a yearlong study of its target planet. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
100 Orbits and Counting - May 6, 2011
Later today, MESSENGER will begin its 100th orbit around Mercury. Since its insertion into orbit about the innermost planet on March 17, the spacecraft has executed nearly 2 million commands.
The data gathered so far include more than 70 million magnetic field measurements, 300,000 visible and infrared spectra of the surface, 16,000 images, and 12,000 X-ray and 9,000 gamma-ray spectra probing the elemental composition of Mercury's uppermost crust.
"As the primary orbital phase of the MESSENGER mission unfolds, we are building up the first comprehensive view of the innermost planet," states MESSENGER Principal Investigator Sean Solomon, of the Carnegie Institution of Washington. "The surface is unraveling before our eyes in great detail, and the planet's topography and gravity and magnetic fields are being steadily filled in. As the Sun becomes increasingly active, Mercury's extraordinarily dynamic exosphere and magnetosphere continue to display novel phenomena."
MESSENGER continues its science-mapping phase in orbit around Mercury. All spacecraft systems remain safe and healthy, and all science instruments are on and continue to collect data according to the baseline observation plan.
"Over the next several weeks, MESSENGER's subsystems and instruments will experience their hottest temperatures yet as the spacecraft crosses between the planet's surface and our Sun at high noon close to the planet, preceded by hour-long eclipses near local midnight with only the spacecraft battery to keep the spacecraft alive in the dark of Mercury's night," notes MESSENGER Project Scientist Ralph McNutt.
"All of this was planned in great detail more than seven years ago, as was the orbit insertion burn that went so flawlessly," he adds. "Theory is one thing and reality another, and the sense of thrill leading to 'firsts' is always followed by a sense of relief, especially in the challenging environment of interplanetary space, far from home."
With less than one-sixth of its primary orbital mission completed, MESSENGER is already rewriting our books on what is known (and unknown) regarding the innermost planet, McNutt says. "By exploring our near — and far — neighbors in our solar system, we touch new knowledge, new understanding, and new wonderment about not only our own origins and place but of the other worlds circling the stars we see in our night sky."
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and entered orbit about Mercury on March 17, 2011 (March 18, 2011 UTC), to begin a yearlong study of its target planet. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
Measuring Mercury's Surface Composition - May 3, 2011
MESSENGER carries a Gamma-Ray Spectrometer (GRS) capable of measuring and characterizing gamma-ray emissions from the surface of Mercury. Gamma rays coming from Mercury carry information about the concentrations of elements present on its surface, and observations from the GRS are being used to determine the surface composition of the planet. Read more to see how these results will be applied to studying the formation and geologic history of Mercury.
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and entered orbit about Mercury on March 17, 2011 (March 18, 2011 UTC), to begin a yearlong study of its target planet. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
Profiling Polar Craters with the Mercury Laser Altimeter - April 26, 2011
MESSENGER's Mercury Laser Altimeter (MLA) will measure the topography or surface relief of the northern hemisphere of Mercury. That data will be used to create topographic maps, which will help characterize the geologic history of the planet. One of the most important tasks for MLA is to measure the depths of craters that are near Mercury's north pole. In the latest "Science Highlights from Mercury's Orbit," MESSENGER's Geophysics discipline group explains why.
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and entered orbit about Mercury on March 17, 2011 (March 18, 2011 UTC), to begin a yearlong study of its target planet. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
Mercury's Exosphere: A Brief Overview - April 19, 2011
One of the primary science goals of MESSENGER is to study Mercury's very thin atmosphere, or exosphere. Although observations of the exosphere from orbit have begun, these data must be carefully calibrated, and analysis is still underway. In the meantime, go online to Highlights-of-Mercury-Science.html for a primer on Mercury's exosphere: what it is, how we observe it, and why it is important.
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and entered orbit about Mercury on March 17, 2011 (March 18, 2011 UTC), to begin a yearlong study of its target planet. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
MESSENGER Kicks Off Yearlong Campaign of Mercury Science - April 4, 2011
This afternoon, MESSENGER began its yearlong science campaign to understand the innermost planet. The spacecraft will fly around Mercury 700 times over the next 12 months, and its instruments will perform the first complete reconnaissance of the cratered planet's geochemistry, geophysics, geological history, atmosphere, magnetosphere, and plasma environment.
"MESSENGER's orbital commissioning phase, which we just completed, demonstrated that the spacecraft and payload are all operating nominally, notwithstanding Mercury's challenging environment," says Principal Investigator Sean Solomon, of the Carnegie Institution of Washington. "With the beginning today of the primary science phase of the mission, we will be making nearly continuous observations that will allow us to gain the first global perspective on the innermost planet. Moreover, as solar activity steadily increases, we will have a front-row seat on the most dynamic magnetosphere–atmosphere system in the Solar System."
MESSENGER's 12-month orbital phase covers two Mercury solar days (one Mercury solar day, from sunrise to sunrise, is equal to 176 Earth days). This means that the spacecraft can view a given spot on the surface under given lighting conditions only twice during the mission, six months apart, making available observation time a precious resource. "So the surface mapping observations had to be planned for the entire year far in advance to ensure coverage of the entire planet under acceptable illumination and viewing geometries," says MESSENGER Deputy Project Scientist Brian Anderson, who oversaw the planning for orbital operations.
SciBox – a suite of software tools for science observation simulation– was developed to help the team choreograph the complicated process of maximizing the scientific return from the mission and minimizing conflicts between instrument observations, while at the same time meeting all spacecraft constraints on pointing, data downlink rates, and onboard data storage capacity. The SciBox tool simulates the entire year of science observations and identifies the best times to take each type of observation. The commands for each week of observations are derived from this full mission analysis.
For instance, Anderson explains, "The remote sensing instruments to measure topography and determine surface and atmospheric composition are fixed on the spacecraft and share the same view direction. Because the ideal viewing directions for these instruments are not the same, we assigned altitude ranges for which the spacecraft pointing is optimized for the science from each instrument. "The camera has its own pivot, so it has much greater freedom in viewing the surface and it takes pictures at all altitudes," he continues. "Several other instruments make measurements of local properties, magnetic field, or charged particles and acquire excellent data regardless of the spacecraft pointing."
SciBox works by finding the best opportunities for each of the instruments to make their measurements and then analyzing how those measurements contribute toward the science goals of the entire mission. "The SciBox tool allows us to plan thousands of science observation activities every week that have to be precisely timed with customized spacecraft pointing," Anderson says.
The observations depend critically on where the spacecraft is in its orbit around Mercury, so the final science observation plan was not generated until the MESSENGER spacecraft completed Mercury orbit insertion. The software commands for this week's instrument operations were sent to MESSENGER only last week.
"We had to wait until after MESSENGER was in orbit before we could start building the actual science sequences that start today, because we needed the actual in-orbit ephemeris as calculated by our navigation team to ensure that images and other pointed observations were taken where planned," explains MESSENGER Payload Operations Manager Alice Berman.
On March 21, her team received the first ephemeris following Mercury orbit insertion, a delivery that provided less than two weeks for each instrument payload lead to generate inputs, test them, and deliver them to the mission operations team. That team then had to merge those science observation commands with the spacecraft operating commands and fully test the entire package.
For example, the command load for this week's observations provides for the acquisition of 4,196 images by the Mercury Dual Imaging System (MDIS). The MDIS team had to check the commands governing each of those images; and the guidance and control team next had to run detailed software simulations on all the science guidance and control commands for the entire week and then add the non-science commands, such as those directing solar panel motions and star trackers. Finally the team re-simulated the full sequence again.
"It's a tremendous amount of work and analysis that has to be done every week," Berman notes. "From our experience with the In-the-Life exercises over the last two years, we determined that we would need three weeks for that process. But our entire team did an outstanding job getting it all done on the accelerated schedule."
Imaging during the MESSENGER flybys provided important reconnaissance for the observations from orbit. During MESSENGER's first six months in orbit, MDIS will create new, higher resolution, global maps of the planet in color and monochrome, acquired under near-ideal viewing conditions.
Emphasis during the second six months will shift to targeted, high-resolution imaging with the MDIS narrow-angle camera and acquisition of a second monochrome map but from a different viewing direction to allow stereoscopic analysis of topography. Additionally,
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and entered orbit about Mercury on March 17, 2011 (March 18, 2011 UTC), to begin a yearlong study of its target planet. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
MESSENGER Sends Back First Image of Mercury from Orbit - March 29, 2011
MESSENGER has delivered its first image since entering orbit about Mercury on March 17. It was taken today at 5:20 am EDT by the Mercury Dual Imaging System as the spacecraft sailed high above Mercury's south pole, and provides a glimpse of portions of Mercury's surface not previously seen by spacecraft. The image was acquired as part of the orbital commissioning phase of the MESSENGER mission. Continuous global mapping of Mercury will begin on April 4.
"The entire MESSENGER team is thrilled that spacecraft and instrument checkout has been proceeding according to plan," says MESSENGER Principal Investigator Sean Solomon, of the Carnegie Institution of Washington. "The first images from orbit and the first measurements from MESSENGER's other payload instruments are only the opening trickle of the flood of new information that we can expect over the coming year. The orbital exploration of the Solar System's innermost planet has begun."
Several other images will be available Wednesday, March 30, in conjunction with a media teleconference at 2 p.m. EDT to discuss the initial orbital images taken from the first spacecraft to orbit Mercury. Media teleconference participants are:
-- Sean Solomon, MESSENGER principal investigator, Carnegie Institution of Washington
-- Eric Finnegan, MESSENGER mission systems engineer, Johns Hopkins University Applied Physics Laboratory, Laurel. Md.
To participate in the teleconference, reporters must contact Dwayne Brown at dwayne.c.brown@nasa.gov or 202-358-1726 for dial-in instructions. During the teleconference, MESSENGER information and images will be available at http://www.nasa.gov/messenger and http://messenger.jhuapl.edu/news_room/presscon8.html.
Audio of the teleconference will be streamed live on NASA's website at: http://www.nasa.gov/newsaudio.
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and entered orbit about Mercury on March 17, 2011 (March 18, 2011 UTC), to begin a yearlong study of its target planet. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
NASA to Release MESSENGER's First Orbital Images Of Mercury - March 28, 2011
NASA will release the first orbital image of Mercury's surface, including previously unseen terrain, on Tuesday afternoon, March 29. Several other images will be available Wednesday, March 30, in conjunction with a media teleconference at 2 p.m. EDT to discuss these initial orbital images taken from the first spacecraft to orbit Mercury.
NASA's MErcury Surface, Space ENvironment, GEochemistry, and Ranging, or MESSENGER, entered orbit March 17 after completing more than a dozen laps within the inner solar system during the past 6.6 years.
Media teleconference participants are:
-- Sean Solomon, MESSENGER principal investigator, Carnegie Institution of Washington
-- Eric Finnegan, MESSENGER mission systems engineer, Johns Hopkins University Applied Physics Laboratory, Laurel. Md.
To participate in the teleconference, reporters must contact Dwayne Brown at dwayne.c.brown@nasa.gov or 202-358-1726 for dial-in instructions.
During the teleconference, MESSENGER information and images will be available at http://www.nasa.gov/messenger.
Audio of the teleconference will be streamed live on NASA's website at: http://www.nasa.gov/newsaudio.
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and entered orbit about Mercury on March 17, 2011 (March 18, 2011 UTC) to begin a yearlong study of its target planet. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
Spacecraft Data Confirm MESSENGER Orbit and Operation - March 21, 2011
Data from its first three days in orbit about Mercury have confirmed the initial assessment of the spacecraft team that MESSENGER is in its intended orbit and operating nominally.
"The team is relieved that things have gone so well, but they remain busy as they continue to configure the spacecraft for orbital operations and monitor its health and safety in the new environment," says MESSENGER Project Manager Peter Bedini, of the Johns Hopkins University Applied Physics Laboratory in Laurel, Md.
Today the navigation team delivered an orbit determination that will span MESSENGER's first four weeks in orbit. Starting on March 23, 2011, the team will begin commissioning the science instruments. That day the Energetic Particle and Plasma Spectrometer, Magnetometer, Mercury Atmospheric and Surface Composition Spectrometer, Mercury Laser Altimeter, Neutron Spectrometer, and X-Ray Spectrometer will be turned on.
On March 29, 2011, the Mercury Dual Imaging System will be powered on and will take its first images. The year-long science observation campaign will begin on April 4, 2011.
"We are about to embark on the first essentially continuous observations of Mercury by an orbiting spacecraft," adds MESSENGER Principal investigator Sean Solomon, of the Carnegie Institution of Washington. "It will be a shared adventure long anticipated and much to be relished."
For complete information on MESSENGER's Mercury orbital operations, view the Flyby Information.
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and after flybys of Earth, Venus, and Mercury will start a yearlong study of its target planet in March 2011. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
MESSENGER Begins Historic Orbit around Mercury - March 17, 2011
At 9:10 p.m. EDT, engineers in the MESSENGER Mission Operations Center at the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Md., received the anticipated radiometric signals confirming nominal burn shutdown and successful insertion of the MESSENGER probe into orbit around the planet Mercury.
The spacecraft rotated back to the Earth by 9:45 p.m. EDT, and started transmitting data. Upon review of these data, the engineering and operations teams confirmed that the burn executed nominally with all subsystems reporting a clean burn and no logged errors.
MESSENGER's main thruster fired for approximately 15 minutes at 8:45 p.m., slowing the spacecraft by 1,929 miles per hour (862 meters per second) and easing it into the planned eccentric orbit about Mercury. The rendezvous took place about 96 million miles (155 million kilometers) from Earth.
"Achieving Mercury orbit was by far the biggest milestone since MESSENGER was launched more than six and a half years ago," says MESSENGER Project Manager Peter Bedini, of APL. "This accomplishment is the fruit of a tremendous amount of labor on the part of the navigation, guidance-and-control, and mission operations teams, who shepherded the spacecraft through its 4.9-billion-mile [7.9-billion-kilometer] journey."
For the next several weeks, APL engineers will be focused on ensuring that MESSENGER's systems are all working well in Mercury's harsh thermal environment. Starting on March 23, the instruments will be turned on and checked out, and on April 4 the primary science phase of the mission will begin.
"Despite its proximity to Earth, the planet Mercury has for decades been comparatively unexplored," adds MESSENGER Principal Investigator Sean Solomon, of the Carnegie Institution of Washington. "For the first time in history, a scientific observatory is in orbit about our solar system's innermost planet. Mercury's secrets, and the implications they hold for the formation and evolution of Earth-like planets, are about to be revealed."
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and after flybys of Earth, Venus, and Mercury will start a yearlong study of its target planet in March 2011. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
MESSENGER On Autopilot for Orbit Insertion - March 16, 2011
MESSENGER is now on autopilot, faithfully executing a detailed set of instructions required to achieve its historic rendezvous with Mercury tomorrow night.
At 8 a.m. Tuesday, all attitude re-orientations planned to control the probe's momentum accumulation and adjust its trajectory were successfully completed. MESSENGER turned to point its high-gain antenna back to Earth for the final stretch of continuous data monitoring until just before the start of Mercury orbit insertion.
The operations team at the Johns Hopkins University Applied Physics Laboratory (APL), in Laurel, Md., has monitored on-board commanded vehicle re-configurations and has sent pre-defined ground commands to establish configurations for the burn.
The science instrument suite has recorded the last set of data for the cruise portion of the mission, and all instruments have been turned off. Although not in an operational mode, the Gamma-Ray Spectrometer has been left in its stand-by mode to ensure thermal stability of the delicate cryogenic cooler. The instruments will be tuned back on as part of orbital commissioning beginning on March 23.
"The navigation team is reporting that there has been little change from the previous targeting estimates, so the spacecraft is on the glide-slope for final approach to Mercury," says MESSENGER Systems Engineer Eric Finnegan.
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and after flybys of Earth, Venus, and Mercury will start a yearlong study of its target planet in March 2011. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
MESSENGER Primed for Mercury Orbit - March 15, 2011
After more than a dozen laps through the inner solar system and six planetary flybys, NASA's MESSENGER spacecraft will move into orbit around Mercury at around 9 p.m. EDT on March 17, 2011. The durable spacecraft — carrying seven science instruments and fortified against the blistering environs near the Sun — will be the first to orbit the innermost planet.
"From the outset of this mission, our goal has been to gather the first global observations of Mercury from orbit," says MESSENGER Principal Investigator Sean Solomon, of the Carnegie Institution of Washington. "At the time of our launch more than six and a half years ago, that goal seemed but a distant dream. MESSENGER is now poised to turn that dream into reality."
Just over 33 hours before the main Mercury orbit insertion maneuver, two antennas from NASA's Deep Space Network — one main antenna and one backup — will begin to track the MESSENGER spacecraft continuously. At 6:30 p.m. EDT on March 17, the number of antennas tracking MESSENGER will increase to five — four of these will be arrayed together to enhance the signal from the spacecraft, and a fifth will be used for backup.
At about 8 p.m., the solar arrays, telecommunications, attitude control, and autonomy systems will be configured for the main thruster firing (known as a "burn"), and the spacecraft, operating on commands transmitted last week from Earth, will be turned to the correct orientation for MESSENGER's Mercury orbit insertion maneuver.
To slow the spacecraft down sufficiently to be "captured" by Mercury, MESSENGER's main thruster will fire for about 15 minutes beginning at 8:45 p.m. This burn will slow the spacecraft by 1,929 miles per hour (862 meters per second) and consume 31 percent of the propellant that the spacecraft carried at launch. Less than 9.5 percent of the usable propellant at the start of the mission will remain after completing the orbit insertion maneuver, but the spacecraft will still have plenty of propellant for orbit adjustments during its yearlong science campaign.
After the burn, the spacecraft will turn toward Earth and resume normal operations. Data will be collected by Deep Space Network antennas and transferred to the Mission Operations Center at the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Md., to be analyzed. It is expected that by 10 p.m. EDT, mission operators will be able to confirm that MESSENGER has been successfully captured into orbit around Mercury.
The maneuver — which will be completed at a time that MESSENGER is more than 96 million miles from Earth — will place the probe into an orbit that brings it as close as 124 miles to Mercury's surface. At 2:47 a.m. EDT on March 18, the spacecraft will begin its first full orbit around Mercury, and the probe will continue to orbit Mercury once every 12 hours for the duration of its primary mission.
"For the first two weeks of orbit, we'll be focused on ensuring that the spacecraft systems are all working well in Mercury's harsh thermal environment," says APL's Eric Finnegan, the MESSENGER Mission Systems Engineer. "Starting on March 23 the instruments will be turned on and checked out, and on April 4 the science phase of the mission will begin and the first orbital science data from Mercury will be returned."
While in orbit, MESSENGER's instruments will perform the first complete reconnaissance of the cratered planet's geochemistry, geophysics, geological history, atmosphere, magnetosphere, and plasma environment.
"The marathon cruise phase of the MESSENGER mission is nearing the finish line," says Solomon. "Like a seasoned runner, the MESSENGER team is positioned to break through the tape. We are extremely excited by the prospect that orbital operations will soon begin."
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and after flybys of Earth, Venus, and Mercury will start a yearlong study of its target planet in March 2011. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
NASA Media Telecon Previews First Spacecraft to Orbit Mercury - March 10, 2011
NASA will host a media teleconference at 1 p.m. EDT on Tuesday, March 15, to discuss the first spacecraft to orbit Mercury.
NASA's MErcury Surface, Space ENvironment, GEochemistry, and Ranging, or MESSENGER, will enter orbit at approximately 9 p.m. EDT on Thursday, March 17. The spacecraft has conducted more than a dozen laps through the inner solar system for the past 6.6 years.
Media teleconference participants are:
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and after flybys of Earth, Venus, and Mercury will start a yearlong study of its target planet in March 2011. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
Ten Days from Mercury Orbit Insertion - March 7, 2011
Ten days from now – on March 17 EDT – the MESSENGER spacecraft will execute a 15-minute maneuver that will place it into orbit about Mercury, making it the first craft ever to do so, and initiating a one-year science campaign to understand the innermost planet.
Starting today, antennas from each of the three Deep Space Network (DSN) ground stations will begin a round-the-clock vigil, allowing flight control engineers at the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Md., to monitor MESSENGER on its final approach to Mercury.
At 10:40 a.m. this morning, the spacecraft began executing the last cruise command sequence of the mission. This command load will execute until next Monday, when the command sequence containing the orbit-insertion burn will start.
"This is a milestone event for our small, but highly experienced, operations team, marking the end of six and one half years of successfully shepherding the spacecraft through six planetary flybys, five major propulsive maneuvers, and sixteen trajectory-correction maneuvers, all while simultaneously preparing for orbit injection and primary mission operations," says MESSENGER Systems Engineer Eric Finnegan. "Whatever the future holds, this team of highly dedicated engineers has done a phenomenal job methodically generating, testing, and verifying commands to the spacecraft, getting MESSENGER where it is today."
The mission operations team now turns its attention to the final preparations for the insertion burn next week and establishing nominal operations for the primary mission. As with the last three approaches to Mercury, the navigation team and the guidance and control team have been successfully using the solar radiation of the Sun to carefully adjust the trajectory of the spacecraft toward the optimum point in space and time to start the orbit-insertion maneuver.
As of the most recent navigation report on February 22, the spacecraft was less than 5 kilometers and less than three seconds from the target arrival point.
"These figures place the spacecraft well within the target corridor for successful orbit insertion," Finnegan says. "Over the next week, additional body and solar-array attitude alternations will further refine this approach and nudge the spacecraft closer to the optimum target location. This approach will require the spacecraft to spend extended amounts of time at attitudes that do not support transmission of telemetry from the spacecraft, so monitoring of the spacecraft over the next week will be conducted with both telemetry and carrier signals."
The in-flight preparations for this historic injection maneuver began on February 8, when several heaters on the spacecraft were configured to condition the bi-propellant used during the maneuver.
"Similar to pre-heating the diesel engine of a truck or car prior to starting in cold weather to allow ignition and prevent damage to the engine, the MESSENGER team turns on and off different heaters on the spacecraft so that the pressures for each of the two propellant species (hydrazine and nitrogen tetroxide) are at the optimum ratio for safe and efficient maneuver execution," Finnegan explains.
Last Wednesday, the engineering and operations teams convened the last detailed review of the injection command sequence. After three iterations of this command sequence, countless Monte-Carlo simulations by the guidance and control team, numerous propulsion modeling simulations, and more than 30 hardware simulations covering all manner of nominal and anomalous operating configurations, the sequence and the associated fault protection configuration have been given the green light to start final preparations for upload to the spacecraft this week.
"The cruise phase of the MESSENGER mission has reached the end game," adds MESSENGER Principal Investigator Sean Solomon, of the Carnegie Institution of Washington. "Orbit insertion is the last hurdle to a new game level, operation of the first spacecraft in orbit about the solar system's innermost planet. The MESSENGER team is ready and eager for orbital operations to begin."
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and after flybys of Earth, Venus, and Mercury will start a yearlong study of its target planet in March 2011. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
A Solar System Family Portrait, from the Inside Out - February 18, 2011
The MESSENGER spacecraft has captured the first portrait of our Solar System from the inside looking out. Comprised of 34 images, the mosaic provides a complement to the Solar System portrait — that one from the outside looking in — taken by Voyager 1 in 1990.
"Obtaining this portrait was a terrific feat by the MESSENGER team," says MESSENGER Principal Investigator Sean Solomon, of the Carnegie Institution of Washington. "This snapshot of our neighborhood also reminds us that Earth is a member of a planetary family that was formed by common processes four and a half billion years ago. Our spacecraft is soon to orbit the innermost member of the family, one that holds many new answers to how Earth-like planets are assembled and evolve."
MESSENGER's Wide Angle Camera (WAC) captured the images on November 3 and 16, 2010. In the mosaic, all of the planets are visible except for Uranus and Neptune, which – at distances of 3.0 and 4.4 billion kilometers – were too faint to detect. Earth's Moon and Jupiter's Galilean satellites (Callisto, Ganymede, Europa, and Io) can be seen in the NAC image insets. The Solar System's perch on a spiral arm of the Milky Way galaxy also afforded a beautiful view of a portion of the galaxy in the bottom center.
"The curved shape of the mosaic is due to the inclination of MESSENGER's orbit from the ecliptic, the plane in which Earth and most planets orbit, which means that the cameras must point up to see some planets and down to see others," explains MESSENGER imaging team member Brett Denevi of the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Md. " The images are stretched to make it easier to detect the planets, though this stretch also highlights light scattered off of the planet limbs, and in some cases creates artifacts such as the non-spherical shape of some planets."
Assembling this portrait was no easy feat, says Solomon. "It's not easy to find a moment when many of the planets are within a single field of view from that perspective, and we have strong Sun-pointing constraints on our ability to image in some directions."
APL's Hong Kang, from MESSENGER's guidance and control team, used the Jet Propulsion Laboratory's Solar System Simulator to pinpoint the relative positions of MESSENGER and the planets to determine if it was possible to see the planets from MESSENGER at any given time. "I then used the celestial coordinates of the planets at the time I wanted to observe them to verify with simulations that MESSSENGER could see each of the planets," Kang explains. "I also used a satellite tool kit to verify that we had the planets in the field of view of MESSENGER's Mercury Dual Imaging System."
The MESSENGER team then had to determine how long the exposures needed to be for each planet. "From exposure times that worked for previous imaging of stars with visual magnitudes similar to those of the planets, we chose exposure times that would allow us to obtain the appropriate number of counts (i.e., amount of light) in each planet image," explains APL's Nori Laslo, the mission's Operations Lead and Instrument Sequencer for MDIS.
"We decided to take images using both the Narrow Angle Camera and the Wide Angle Camera for each planet so that we would cover the sky surrounding the planets and also image the planets themselves at as high a resolution as possible," she adds. "I took all of these parameters, along with a variety of related settings, and began building the command sequence with the library of MDIS commands that we have to configure and control the camera system."
Robin Vaughan, who worked with Kang to coordinate the pointing and timing of the MDIS, also played a role in Voyager's portrait.
"I was working as an optical navigation analyst at JPL for the Voyager Neptune encounter," says Vaughan, the lead engineer for MESSENGER's guidance and control (attitude control) subsystem at APL. "I had to plan and generate the pointing commands for pictures of Neptune and its satellites against background stars that we used to improve our estimate of the spacecraft's trajectory leading up to the Neptune encounter. Voyager's solar system portrait was done a few years after that flyby and was coordinated by the imaging team. Our optical navigation image planning software was used to double check the pointing commands they had designed and confirm what they expected to see in each image."
Vaughan did the same thing for MESSENGER's portrait, using Kang's designs. "I used the SPICE trajectory files for the spacecraft generated by MESSENGER's navigation team, as well as routines in the SPICE toolkit, to write a software program that would identify windows when each of the planets would be visible to MDIS given the constraints on pivot angle and Sun keep-in zone for spacecraft attitude," she says.
From a technical standpoint, the MESSENGER portrait was a little more complicated than what was done for Voyager because scientists had to stay within the Sun keep-in constraints. "With Voyager so far out in the solar system, the Sun is much fainter and there were no constraints on the overall spacecraft attitude as far as the Sun was concerned," Vaughan says. "Being in the inner solar system, MESSENGER has to constantly keep the sunshade pointing toward the Sun, which limits the periods when the different planets can be viewed even with the extra degree of freedom that MDIS has with its pivot capability."
Denevi says the experiment was humbling. "Seeing our solar system as just these little specks of light, it reminds you of how lucky we are that we've had the chance, through so many missions, to get up close and explore the incredible diversity and geology that each planet and moon displays," she says. "Mercury has been just a dot on the horizon for most of history, and we get to fill in the details and know it as a real world. What an amazing opportunity!"
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and after flybys of Earth, Venus, and Mercury will start a yearlong study of its target planet in March 2011. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
One Month Until Mercury Orbit Insertion - February 17, 2011
After more than a dozen laps through the inner solar system, NASA's MESSENGER spacecraft will move into orbit around Mercury on March 17, 2011. The durable spacecraft — carrying seven science instruments and fortified against the blistering environs near the Sun — will be the first to orbit the innermost planet.
At 8:45 p.m. EDT, MESSENGER — having pointed its largest thruster very close to the direction of travel — will fire that thruster for nearly 14 minutes, with other thrusters firing for an additional minute, slowing the spacecraft by 862 meters per second (1,929 miles per hour) and consuming 31% of the propellant that the spacecraft carried at launch. Less than 9.5% of the usable propellant at the start of the mission will remain after completing the orbit insertion maneuver, but the spacecraft will still have plenty of propellant for future orbit correction maneuvers.
The orbit insertion will place the spacecraft into an initial orbit about Mercury that has a 200 kilometer (124 mile) minimum altitude and a period of 12 hours. At the time of orbit insertion, MESSENGER will be 46.14 million kilometers (28.67 million miles) from the Sun and 155.06 million kilometers (96.35 million miles) from Earth.
"The journey since launch, more than six and a half years ago, has been a long one," says MESSENGER Principal Investigator Sean Solomon, of the Carnegie Institution of Washington. "But we have rounded the last turn, and the finish line for the mission's cruise phase is in sight. The team is ready for orbital operations to begin."
Engineers recently tested the arrayed-antenna configuration that will be used during the Mercury orbit insertion. During the maneuver, MESSENGER's orientation will be optimized to support the burn, not to support communications with the team on the ground. As a result, the signal home will be weaker than usual. To boost the signal, communications engineers will use four antennas at the Goldstone Deep Space Communications Complex — one 70-meter dish and three 34-meter dishes.
"This arrangement is not typical for a maneuver, so we wanted to do a few dry runs before orbit insertion," says MESSENGER Communications Engineer Dipak Srinivasan, of the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Md. "We are still analyzing the data, but everything went as expected."
Since the last deep-space maneuver (DSM) almost a year and a half ago, the primary focus of the team has been on preparing for the orbit insertion maneuver and for orbital operations. Detailed plans have been developed and vetted through an extensive series of meetings ranging from internal peer reviews of each subsystem to formal reviews with external experts assessing overall readiness. Three of the major reviews were dedicated specifically to the activities associated with the MOI maneuver itself.
In addition to taking advantage of planned DSMs to practice aspects of the orbit insertion maneuver, the team has conducted a number of flight tests to characterize key subsystem behavior and to confirm the proper operation of various spacecraft components. Three full-team rehearsals using the hardware simulator have been conducted to practice all activities to be followed during the upcoming maneuver. The first of these exercises mimicked a nominal orbit insertion, and the following two presented anomalies for the team to recognize, analyze, and address.
"Although we feel that the preparations to date – and those scheduled for the next month – have been well thought-out, that the decisions made to define the specific activities were sound, and that the level of review and rehearsal has been more than adequate, we recognize the extraordinary complexity and unique nature of this endeavor," says APL's Peter Bedini, MESSENGER's project manager. "But at this point, four weeks out, we are well positioned for success. The spacecraft is healthy, continues to operate nominally, and is on course to be at the right place at the right time at 8:45 P.M. ET on the evening of March 17."
For an overview of Mercury Orbit Insertion and planned orbital observations, view the Flyby Information.
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and after flybys of Earth, Venus, and Mercury will start a yearlong study of its target planet in March 2011. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
One Hundred Days until Mercury Orbit Insertion - December 7, 2010
One hundred days from now, MESSENGER will execute a 15-minute maneuver that will place the spacecraft into orbit about Mercury, making it the first craft ever to do so, and initiating a one-year science campaign to understand the innermost planet. It has already been 14 years since this mission was first proposed to NASA, more than 10 years since the project officially began, and over six years since the spacecraft was launched.
A multitude of milestones have been passed on the way toward the primary science phase of the mission, including six planetary flybys and five deep-space maneuvers. This week the team has completed a milestone of a different sort: the orbital readiness review.
Today's review was the culmination of more than one year of major reviews designed to confirm the readiness of all mission elements to achieve orbit about Mercury next March and to begin orbital operations shortly thereafter.
"For this and many reviews before it we have called on a number of experts outside the MESSENGER project, from both APL and outside institutions, to review our plans to see where there are gaps or weak spots," explains MESSENGER Project Manager Peter Bedini of the Johns Hopkins University Applied Physics Laboratory. "The intent is to tap the knowledge-base of those who have lived through similar challenges, and to make any adjustments that promise to improve the chances of success in our prime mission."
"There is still work to do in preparation for orbit insertion next March, and those preparations will also be reviewed, but today's review was the last in a long series laid out more than a year ago," Bedini adds.
"MESSENGER has been on a long journey," adds MESSENGER Principal Investigator Sean Solomon of the Carnegie Institution of Washington, "but the promised land lies ahead. All of the preparations for orbit insertion and orbital operations by the project team and the mission's many review panels have served to maximize the likelihood that the intensive exploration of the innermost planet will begin smoothly and efficiently 100 days from now."
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and after flybys of Earth, Venus, and Mercury will start a yearlong study of its target planet in March 2011. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
The Smithsonian Institution and SAE International (formerly the Society for Automotive Engineers) have honored papers published by scientists on the MESSENGER team.
MESSENGER Thermal Engineer Carl J. Ercol was selected to receive the 2008 SAE Wright Brothers Medal Award for his paper of that year entitled "Return to Mercury: An overview of the MESSENGER spacecraft thermal control system design and up-to-date flight performance."
The medal is awarded to the author of the best paper presented at an SAE meeting relating to the invention, development, design, construction, or operation of an aircraft and/or spacecraft. The award considers the value of the author's contribution to the state-of-the-art in the furtherance of flight technology whether it pertains to aircraft or spacecraft systems or their parts, components, subsystems, or accessories. Ercol will receive his award at the SAE 2011 AeroTech Congress & Exhibition in Toulouse, France, in October 2011.
MESSENGER Participating Scientist Thomas R. Watters has been awarded the Smithsonian Secretary's Research Prize for the paper, "Evolution of the Rembrandt impact basin on Mercury," which was published in Science magazine last year. Watters is a senior scientist at the Center for Earth and Planetary Studies of the National Air and Space Museum. The award, which comes with a $2,000 award to the winner's research account, seeks to recognize and promote good scholarship across the Smithsonian Institution.
"MESSENGER is a technically challenging mission of scientific discovery," notes Principal Investigator Sean Solomon of the Carnegie Institution of Washington. "It is wonderful that these latest awards recognize that the MESSENGER spacecraft is meeting its substantial engineering challenges and at the same time providing new insights into the nature and evolution of the inner planets."
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and after flybys of Earth, Venus, and Mercury will start a yearlong study of its target planet in March 2011. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
MESSENGER Team Completes Two-Week Orbital Flight Test - September 3, 2010
The MESSENGER team has just wrapped up a two-week flight test to ensure that the Mercury-bound spacecraft is ready for orbital operations. On March 18, 2011, MESSENGER will become the first spacecraft to enter into orbit about Mercury, embarking on a year-long mission to study in depth the planet closest to the Sun. The completion of this recent test provides a high-fidelity verification of the tools, processes, and procedures that are needed to conduct flight operations at Mercury.
"Even though we have more than six months to go until orbit, we wanted to do this test now to make sure that we had enough time to make adjustments," says MESSENGER Mission Operations Manager Andy Calloway, of the Johns Hopkins University Applied Physics Laboratory in Laurel, Md., "But everything worked as expected. We have proven, not just in the ground tests but now in flight, that the sequences and planned daily activities can be conducted safely and as expected. We are quite pleased with the results."
The flight test took place from August 17 to August 29. In order to force the spacecraft to rotate in space and to gather science data in a manner similar to the operations the probe will experience during the orbital phase of the mission, the ephemerides used onboard the spacecraft had to be modified. "We had to convince the spacecraft that it was in Mercury orbit," Calloway says. "We also intentionally chose a two-week period with Sun and Earth geometries similar to those that MESSENGER will see during the orbital phase of the mission. The goal was to exercise the flight system in flight conditions as nearly identical as possible to those that will be experienced in orbit to validate performance, and to run as many of the same processes as possible to match a typical fortnight of orbital operations."
In support of the two-week flight test, team members worked with NASA's Deep Space Network (DSN) schedulers and engineers to put in place an orbit-like track schedule that is very different from cruise. This schedule consists of daily contacts to play back stored data, upload commands, and monitor vehicle health, while pointing the high-gain antenna at Earth, plus about five hours a day for radio science measurements while the spacecraft points away from Earth and conducts science operations.
"During MESSENGER's cruise phase, we typically have had three to four DSN tracks a week, for about six to eight hours each," Calloway says. "But during orbit we will be tracking the spacecraft for 13 hours a day, including weekends and holidays. We needed to see if that was a realistic track schedule and one that we could maintain with our staffing plan, ground tools, and automation scripts."
Approximately once a week during orbit, mission operators will perform brief propulsive maneuvers, where they fire MESSENGER's small thrusters to unload angular momentum that builds up in the probe's reaction wheel assemblies due to continuous external forces pushing on the spacecraft – primarily from the Sun. "During the test, they performed three such maneuvers successfully," says APL's Eric Finnegan, the MESSENGER Systems Engineer. "We were able to demonstrate that such momentum management actions can be executed safely and routinely without any impact to science data gathering."
During the two weeks of the test, the team also exercised a variety of orbit-like scenarios and activities, including eclipse power management, star tracker management, quick data acquisition, variable downlink data-rate changes, command timing biases, weekly ephemeris loads, bi-weekly command loads, and instrument memory checks.
During the second half of the test, the science instruments conducted a series of observations as if the spacecraft were in orbit about Mercury. For example, the Mercury Dual Imaging System collected more than 1,400 images, as if mapping the planet, and the Mercury Laser Altimeter fired four times over the course of two days, as if ranging to the planet's surface. The command sequence directing these activities was generated using the mission's automated science-planning tool, as all sequences will be during the prime mission.
"Our entire cruise phase and even the three Mercury flybys have only been warm-ups for the main event of our mission," says MESSENGER Principal Investigator Sean Solomon, of the Carnegie Institution of Washington. "These two weeks of flight tests have been our dress rehearsal, to ensure that our spacecraft and our flight team are ready for opening night."
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and after flybys of Earth, Venus, and Mercury will start a yearlong study of its target planet in March 2011. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
Vulcanoid Search Continues as MESSENGER Reaches Orbital Perihelion - August 17, 2010
Today MESSENGER will pass within 0.308 astronomical units (AU) of the Sun (one AU is Earth's distance from the Sun, approximately 150 million kilometers or 93 million miles), providing MESSENGER scientists with another opportunity to search for vulcanoids. Named after the hypothetical planet Vulcan, whose existence was disproven in 1915, vulcanoids are asteroids that orbit the Sun inside the orbit of the planet Mercury.
No vulcanoids have yet been discovered, and it is not known if any exist. But should they be found, these small, rocky asteroids may yield insights into the formation and early evolution of the solar system. They might contain material left over from the earliest period of planet formation and help determine the conditions under which the terrestrial planets, particularly Mercury, formed. Vulcanoids would also represent an additional population of impactors that contributed to the cratering history of Mercury much more than that of any other body. Impacts by vulcanoids would make the planet's surface appear older, relative to the surfaces of the Moon and other inner planets, than it actually is.
If they do exist, the vulcanoids would be difficult to spot. First, they would be very small – less than 60 kilometers (37 miles) in diameter (a limit set by Earth-based observations) – and their reflected light would generally be drowned out by the bright glare of the nearby Sun. Because of their proximity to the Sun, searches for vulcanoids from the ground can be carried out only during twilight or or dawn or during solar eclipses.
The mission's imaging team is taking advantage of the probe's proximity to the region of space inside Mercury's orbit during this perihelion to continue their search for vulcanoids. The latest search started on August 14 and continues through today.
"Our searches for vulcanoids may not turn up any objects," says MESSENGER principal investigator Sean Solomon, of the Carnegie Institution of Washington, "but a discovery of even one vulcanoid would change our thinking about the evolution of Mercury. The solar system still has many surprises in store for us, so it makes sense for us to be ready for the unexpected."
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and after flybys of Earth, Venus, and Mercury will start a yearlong study of its target planet in March 2011. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
AGU Selects MESSENGER Paper as Eos Research Spotlight - July 20, 2010
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and after flybys of Earth, Venus, and Mercury will start a yearlong study of its target planet in March 2011. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
MESSENGER Reveals New Information about Mercury's Exosphere, Volcanism, and Magnetic Substorms - July 15, 2010
Observations of the ionized calcium (Ca+) in Mercury's tail region. Image A shows observed column emissions projected onto the plane containing the Sun-Mercury line and Mercury's spin axis, interpolating to fill-in unobserved regions. To clearly show the full region scanned, all observations below 10 R (1 on the color scale) have been set equal to 10 R, leading to the blue background. Beyond 6 Mercury radii "downtail," no observations are above the noise level. In Image B, the red spectrum is an average of the ionized calcium emission-line observations between 1.5–3.5 Mercury radii (one-standard-deviation uncertainties are shown); the green line is a Gaussian fit to the average Ca+ line. Image C is a schematic illustration of the magnetospheric convection pattern (blue arrows) that concentrates Ca+ in the observed narrow region before the ions are ejected down the tail. The large arrow indicates the approximate position of the observed Ca+ emission tailward of the magnetospheric X-line.
MESSENGER Mercury Dual Imaging System (MDIS) narrow-angle camera image of a diffuse, high-reflectance halo over 200 kilometers in extent surrounding an irregularly shaped, rimless, steep-walled depression approximately 30 kilometers in diameter (arrow). The inset is an enhanced-color view of the bright halo overlying a high-reflectance smooth plains unit that embays Rachmaninoff crater to the north and east (north is up).
Schematic view of Mercury's magnetosphere in its ground state and during moderate and extreme tail loading, observed by the MESSENGER spacecraft on September 29, 2009.
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and after flybys of Earth, Venus, and Mercury will start a yearlong study of its target planet in March 2011. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
Two members of the MESSENGER team have been honored by their peers. Carl Jack Ercol, the man largely responsible for ensuring that MESSENGER can withstand solar radiation up to 11 times greater than at Earth as it orbits the planet closest to the Sun, has received the 2008 SAE Arch T. Colwell Merit Award. Independently, MESSENGER Co-Investigator James W. Head, III, was awarded the Runcorn-Florensky Medal by the European Geosciences Union (EGU) at their General Assembly earlier this month.
SAE International, a global association of more than 128,000 engineers and related technical experts in the aerospace, automotive, and commercial-vehicle industries, annually recognizes authors of papers of outstanding technical or professional merit presented at a meeting of the society during the calendar year. Papers are judged primarily for their value as new contributions to existing knowledge of mobility engineering.
Ercol, MESSENGER's thermal engineer, received the Colwell award in recognition of, "Return to Mercury: An overview of the MESSENGER spacecraft thermal control system design and up to date flight performance." Read more about Ercol.
The Runcorn-Florensky medal – established by the EGU's Division on Planetary and Solar System Sciences in recognition of the scientific achievements of Keith Runcorn and Cyril Florensky – is intended to honor scientists who've made exceptional contributions to planetology.
Head, a professor of Geological Sciences at Brown University, was cited for his work on volcanism and tectonism in the formation and evolution of planetary crusts and for developing a series of remarkable U.S.-European research collaborations in Earth and planetary science.
"The entire MESSENGER team is delighted that our two colleagues have been recognized for their outstanding contributions," offers MESSENGER Principal Investigator Sean Solomon, of the Carnegie Institution of Washington. "That MESSENGER has survived nearly six years in an orbit that takes it as close to the Sun as Mercury's perihelion distance is in no small part the result of the thorough analysis and creative solutions that Jack brought to the thermal design of our spacecraft. Jim's deep knowledge of the geology of the inner planets has been critical to the analysis of MESSENGER's observations of Mercury, and there is no one in the planetary geology community who has done more than Jim to further cooperation in scientific space exploration between the U.S. and both eastern and western Europe."
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and after flybys of Earth, Venus, and Mercury will start a yearlong study of its target planet in March 2011. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
Jack Trombka, a MESSENGER Co-Investigator and member of the Science Team's Geochemistry Group, was recently awarded the NASA Distinguished Public Service Medal, NASA's highest honor. The award is granted only to individuals whose distinguished accomplishments contributed substantially to the NASA mission.
Trombka's contributions to the exploration of space stretch back more than four decades. Currently an Emeritus Senior Fellow in Goddard's Astrochemistry Laboratory, he began his career in the space sciences at the Jet Propulsion Laboratory, where he worked on the Ranger gamma-ray spectrometer and more generally studied the applications of X-ray, gamma-ray, and neutron spectrometry to planetary remote and in-situ geochemical analysis.
Trombka has been an instrument principal investigator or co-investigator on many lunar and planetary science missions, including the U.S. Apollo, Viking, Solar Maximum, Mars Observer, WIND, NEAR, Mars Odyssey, and Lunar Reconnaissance Orbiter missions and the Russian Luna, Mars, and Phobos missions.
As a member of MESSENGER's Science Team, he played a key role in the development of the X-Ray Spectrometer and Gamma-Ray and Neutron Spectrometer instruments and will participate in the analysis of their measurements.
"Jack has been deeply involved in MESSENGER since the first development of the mission concept 14 years ago," states mission Principal Investigator Sean Solomon, of the Carnegie Institution of Washington. "The entire MESSENGER team is delighted that NASA has recognized Jack's exceptionally broad contributions to the field of planetary chemistry, and we will be counting on that breadth of experience as we start to unravel the chemical composition of Mercury's crustal materials."
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and after flybys of Earth, Venus, and Mercury will start a yearlong study of its target planet in March 2011. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
MESSENGER Team Rehearsing for Mercury Orbital Operations - April 13, 2010
It's not easy practicing for something no one has done before, but the MESSENGER team is giving it a go. Mission and science operators have wrapped up the third and fourth in a series of rehearsals for how the spacecraft will be operated once it is in orbit about Mercury.
"No spacecraft has orbited Mercury before; although the spacecraft has been operating since 2004 and has flown past Mercury three times, team members have no direct experience planning and scheduling daily science observations and data playback in such an environment," says Alice Berman, MESSENGER's payload operations manager at the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Md. "So we're working now, before we go into orbit, on a readiness plan to ensure that the mission's full science success criteria will be met."
That plan includes Week-in-the-Life tests (or "WITLs"), which simulate one or more weeks in orbital operations to test the new procedures and software being developed for the Mercury orbital mission.
"Once in orbit, we'll prepare and upload a new command load, containing merged instructions for the spacecraft and science instruments, once a week," says Berman. "It will take three weeks to prepare and validate each command load. Therefore, the science and mission operations teams will be working on multiple staggered command loads at any given time during the orbit year."
The first two WITL exercises – completed in 2009 – focused on new procedures and software. These built upon the lessons learned and improvements from the Day-in-the-Life tests that began in 2007. "One of the most critical new software tools is called SciBox, which plans the detailed science instrument activities for the entire orbital mission," Berman explains. "Most of the planning steps were practiced over an extended period to give teams enough time to learn the new process and software and train others on their teams." The initial exercises led to several software improvements.
This latest exercise focused on rehearsing the new process in a simulated timeframe typical of orbital operations. The Operations Team wanted to answer two questions: Can the planning process be accomplished in the defined timeframe? And can processes and procedures be further streamlined?
From January 25 to February 17, the team planned activities through SciBox, tested them to make sure they worked, and began implementing them while starting a new set of commands.
"The team clearly showed that it could perform the planning process within the given timeframe," Berman says, reporting back from the March 24 debriefing meeting. "Furthermore, the teams demonstrated the ability to meet the schedule despite the blizzards that closed the Lab for several days in February."
The remaining WITL tests will be completed in 2010. Exercises five through eight are planned to start this month, with four consecutive weeks being planned over a six-week period. This summer, additional exercises will be run to simulate contingency or anomaly situations that involve rework or replanning on a short schedule.
"By this fall, we plan to complete WITL exercises covering at least 10 different weeks and orbital conditions," Berman says. "It is critical to test the many different observing scenarios and orbital conditions the spacecraft will face when it orbits Mercury."
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and after flybys of Earth, Venus, and Mercury will start a yearlong study of its target planet in March 2011. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
One Year until Mercury Orbit Insertion - March 18, 2010
One year from today — starting at 12:45 a.m. UTC — MESSENGER will transition from orbiting the Sun to being the first spacecraft ever to orbit the planet Mercury.
"We are finally closing in on the most intense phase of the mission," says MESSENGER Principal Investigator Sean Solomon, of the Carnegie Institution of Washington. "MESSENGER's six and a half years of interplanetary flight are a long warm-up for the main event, when we are in orbit about Mercury. The final year of that flight will be a busy time for the team, as we review orbital operation plans for all spacecraft subsystems."
Entering orbit about Mercury will require the probe to perform the largest propulsive maneuver of the entire mission. For Mercury orbit insertion (MOI), MESSENGER will point its largest thruster very close to the direction of travel and fire that thruster for nearly 14 minutes as well as other thrusters for an additional minute, slowing the spacecraft by 862 meters per second (1,929 miles per hour) and consuming 31% of the propellant that the spacecraft carried at launch.
Click here for an animation of the orbit insertion maneuver and initial orbit of Mercury. Two animations and various perspective views of the orbit insertion maneuver and initial orbit of Mercury are available here.
"Less than 9.5% of the usable propellant at the start of the mission will remain after completing the orbit insertion maneuver, but the spacecraft will still have plenty of propellant for future orbit correction maneuvers," says MESSENGER Mission Design Engineer Jim McAdams of the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Md.
MESSENGER engineers recently tweaked the strategy for entering into orbit about Mercury. "MESSENGER's propulsion system has consistently performed with high accuracy," McAdams explains. "We replaced an MOI clean-up maneuver with a placeholder for a contingency clean-up maneuver, which reduces risk by simplifying the orbit insertion process."
Another change affecting the orbit insertion is a shift in the spacecraft orbit's tilt relative to Mercury's equatorial plane, from 80.0° to 82.5°, "a carefully studied change that will improve overall science data returned during the Mercury orbital phase," McAdams says.
The orbit insertion will place the spacecraft into an initial orbit about Mercury that has a 200 kilometer (124 mile) minimum altitude and a period of 12 hours. At the time of orbit insertion, MESSENGER will be 46.14 million kilometers (28.67 million miles) from the Sun and 155.06 million kilometers (96.35 million miles) from Earth.
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and after flybys of Earth, Venus, and Mercury will start a yearlong study of its target planet in March 2011. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
Ten Craters on Mercury Receive New Names - March 16, 2010
The International Astronomical Union (IAU) recently approved a proposal from the MESSENGER Science Team to confer names on 10 impact craters on Mercury. The newly named craters were imaged during the mission's three flybys of Mercury in January and October 2008 and September 2009.
The IAU has been the arbiter of planetary and satellite nomenclature since its inception in 1919. In keeping with the established naming theme for craters on Mercury, all of the craters are named after famous deceased artists, musicians, or authors.
"All of the newly named features figure importantly in ongoing analysis of Mercury's geological history," says MESSENGER Principal Investigator Sean Solomon of the Carnegie Institution of Washington. "The MESSENGER Science Team is pleased that the IAU has responded promptly to our latest request for new names, so that the identities of these craters in the scientific literature can be clearly conveyed."
The newly named craters include:
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and after flybys of Earth, Venus, and Mercury will start a yearlong study of its target planet in March 2011. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
MESSENGER's Odometer Reading: Four Billion Miles! - February 27, 2010
Today the MESSENGER spacecraft crossed the four-billion-mile mark since its launch. The probe has completed about 81 percent of its journey toward its destination to be the first spacecraft to orbit the planet Mercury.
That MESSENGER's odometer reading has reached another major milestone reminds us of the long and complex route that our spacecraft must follow. Mercury orbits deep within the Sun's gravity well. So, even though the planet can be as close as 82 million kilometers (51 million miles) from Earth, getting the probe into orbit around Mercury depends on an innovative trajectory that uses the gravity of Earth, Venus, and Mercury itself to slow and shape the probe's descent into the inner solar system.
On its 4.9 billion-mile trek, MESSENGER has flown by Earth once, Venus twice, and Mercury three times.
"Four billion miles, more than 43 times Earth's distance from the Sun, is an impressive figure," says MESSENGER Principal Investigator Sean Solomon, of the Carnegie Institution of Washington. "But MESSENGER is a well-built vehicle, with many more miles of productive work ahead. The Mercury orbital phase of our mission is barely one year away, and the team is hard at work to ensure that we are ready for the intensive activity that awaits."
Throughout its long journey toward the orbital phase of the mission, MESSENGER has remained quite busy. In addition to completing six planetary flybys and five deep-space maneuvers, a wide variety of tests have been conducted to characterize the performance of the science payload and the spacecraft subsystems.
On February 22, the team conducted the first in a series of short solar-array-offset-characterization tests. "These exercises are designed to improve our model of solar-array performance prior to orbit, and each is a simple test that can be executed in a few minutes without load management," explained MESSENGER Mission Project Manager Peter Bedini, of The Johns Hopkins University Applied Physics Laboratory.
The test measures the output of each solar array wing individually by placing it at a 72° Sun-offset angle. During the 5-minute measurement, the other wing is rotated off of the Sun at 95° so that it contributes no power. The measurement will be repeated at several solar distances to allow for correlation of results with those from earlier tests at ~0.5 astronomical units (AU), as well as additional insight into orbit performance at ~0.3 to 0.45 AU.
MESSENGER will enter orbit about Mercury on March 18, 2011.
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and after flybys of Earth, Venus, and Mercury will start a yearlong study of its target planet in March 2011. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
MESSENGER Team Releases First Global Map of Mercury - December 15, 2009
NASA's MESSENGER mission team and cartographic experts from the U. S. Geological Survey have created a critical tool for planning the first orbital observations of the planet Mercury – a global mosaic of the planet that will help scientists pinpoint craters, faults, and other features for observation. The map was created from images taken during the MESSENGER spacecraft's three flybys of the planet and those of Mariner 10 in the 1970s. A presentation on the new global mosaic is being given today at the Fall Meeting of the American Geophysical Union in San Francisco.
The MESSENGER spacecraft completed its third and final flyby of Mercury on September 29, concluding its reconnaissance of the innermost planet. The MESSENGER team has been busily preparing for the yearlong orbital phase of the mission, beginning in March 2011, and the near-global mosaic of Mercury from MESSENGER and Mariner 10 images is key to those plans.
"The production of this global mosaic represents a major milestone for everyone on the MESSENGER imaging team," says MESSENGER Principal Investigator Sean Solomon of the Carnegie Institution of Washington. "Beyond its extremely important use as a planning tool, this global map signifies that MESSENGER is no longer a flyby mission but instead will soon become an in-depth, non-stop global observatory of the Solar System's innermost planet."
"The process of making a mosaic may seem relatively straightforward—simple software can stitch together panoramas from multiple images. However, the challenging part has been to make cartographically accurate maps from a series of images with varying resolution (from about 100 to 900 meters per pixel) and lighting conditions (from noontime high Sun to dawn and dusk) taken from a spacecraft traveling at speeds greater than 2 kilometers per second (2,237 miles per hour)," says Arizona State University's Mark Robinson, a member of the MESSENGER Science Team.
Small uncertainties in camera pointing and changes in image scale can introduce small errors between frames, he says. "And with lots of images, small errors add up and lead to large mismatches between features in the final mosaic. By picking control points—the same features in two or more images—the camera pointing can be adjusted until the image boundaries match." This operation is known as a bundle-block adjustment and requires highly specialized software.
Cartographic experts at the USGS Astrogeology Science Center in Flagstaff, Ariz., picked the control points to solve the bundle-block adjustment to construct the final mosaic using the Integrated Software for Imagers and Spectrometers (ISIS). For the MESSENGER mosaic, 5,301 control points were selected, and each control point on average was found in more than three images (18,834 measurements) from a total of 917 images. Scientists at ASU and the Johns Hopkins University Applied Physics Laboratory (APL) were also instrumental in making the mosaic possible.
"This mosaic represents the best geodetic map of Mercury's surface. We want to provide the most accurate map for planning imaging sequences once MESSENGER achieves orbit around Mercury", says Kris Becker of the USGS. "As the systematic mapping of Mercury's surface progresses, we will continually add new images to the control point network, thus refining the map", he says. "It has already provided us with a start in the process of naming newly identified features on the surface."
In the final bundle-block adjustment the average error was about two-tenths of a pixel or only about 100 meters—which is an excellent match from image-to-image. The biggest remaining issue is the absolute control of features on the surface. For instance, if the north pole is not precisely at the spin axis you could have a mosaic in which all the seams overlapped perfectly, but the whole mosaic could slide around like the skin of an orange that somehow became detached from the interior fruit.
Much work was done with the Mariner 10 images collected in 1974 and 1975 to make an absolute control network even though only 45% of the planet was seen at the time. The longitude system for Mercury is tied to a small crater named Hun Kal (the number twenty in an ancient Mayan language, because the crater is centered at 20°W). For now, MESSENGER data are tied to the earlier Mariner 10 control network.
Absolute positional errors in the new mosaic are about two kilometers, according to the MESSENGER team. Once the MESSENGER spacecraft orbits Mercury, much progress will be made refining the relative and absolute control of the MESSENGER (and Mariner 10) images, and the entire planet will be imaged at even higher resolution. The global mosaic is available for download on the USGS Map-a-Planet web site, http://www.mapaplanet.org.
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and after flybys of Earth, Venus, and Mercury will start a yearlong study of its target planet in March 2011. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
Deep-Space Maneuver Positions MESSENGER for Mercury Orbit Insertion - November 24, 2009
The Mercury-bound MESSENGER spacecraft completed its fifth and final deep-space maneuver of the mission today, providing the expected velocity change needed to place the spacecraft on course to enter into orbit about Mercury in March 2011. A 3.3-minute firing of its bi-propellant engine provided nearly all of the probe's 177 meter per second (396 mile per hour) increase in its speed relative to the Sun.
MESSENGER was 230.4 million kilometers (143.2 million miles) from Earth when today's maneuver began at 4:45 p.m. EST. Mission controllers at The Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Md., verified the start of the maneuver about 12 minutes, 49 seconds later, when the first signals indicating spacecraft thruster activity reached NASA's Deep Space Network tracking station outside Goldstone, Calif.
"The team was well-prepared for the maneuver," said MESSENGER Mission Systems Engineer Eric Finnegan, of APL. "Initial data analysis indicates an extremely accurate maneuver execution. After sifting through all the post-burn data I expect we will find ourselves right on target."
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and after flybys of Earth, Venus, and Mercury will start a yearlong study of its target planet in March 2011. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
Time Magazine Names MESSENGER One of the Best Inventions of 2009 - November 17, 2009
The MESSENGER spacecraft has been named one of Time magazine's best 50 inventions of 2009. The NASA probe, built by the Applied Physics Laboratory (APL) in Laurel, Md., came in at number 11. Here is what the editors had to say in the November 23 issue of the magazine:
"If the solar system has a flame-roasted planet, it's Mercury, where the sun pushes surface temperatures to 800°F (426°C). That brutal environment is one reason no NASA probe has visited Mercury since 1975. But Messenger — the space agency's new Mercury ship — can take the heat. Having just completed a flyby a mere 141 miles (228 km) above the planet's surface, it's preparing to enter Mercury's orbit in 2011. The probe will survey parts of the world never before seen — and will do so in comfort. Covered in an insulating ceramic skin, it will endure temperatures of 700°F (370°C) on its exterior; inside, it will operate at a room-temperature 70°F (20°C)."
"MESSENGER has certainly had to face a number of novel technical challenges for a deep-space mission, and it's nice to see our engineering team recognized in this manner by the editors and writers of Time," offers MESSENGER principal investigator Sean Solomon of the Carnegie Institution of Washington. "Our entire team is looking forward to the time, 16 months from now, when our 'invention' will be the first spacecraft to orbit Mercury."
The full list of Time's "Best Inventions," is available online at
http://www.time.com/time/specials/packages/completelist/0,29569,1934027,00.html.
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and after flybys of Earth, Venus, and Mercury will start a yearlong study of its target planet in March 2011. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
MESSENGER SPACECRAFT REVEALS MORE HIDDEN TERRITORY ON MERCURY - November 3, 2009
Dwayne Brown
Headquarters, Washington
202-358-1726
dwayne.c.brown@nasa.gov
Paulette Campbell
Johns Hopkins University Applied Physics Laboratory, Laurel, Md.
240-228-6792
paulette.campbell@jhuapl.edu
RELEASE: 09-257
MESSENGER SPACECRAFT REVEALS MORE HIDDEN TERRITORY ON MERCURY
WASHINGTON -- A NASA spacecraft's third and final flyby of the planet Mercury gives scientists, for the first time, an almost complete view of the planet's surface and provides new scientific findings about this relatively unknown planet.
The Mercury Surface, Space Environment, Geochemistry and Ranging spacecraft, known as MESSENGER, flew by Mercury on Sept. 29. The probe completed a critical gravity assist to remain on course to enter into orbit around Mercury in 2011. Despite shutting down temporarily because of a power system switchover during a solar eclipse, the spacecraft's cameras and instruments collected high-resolution and color images unveiling another 6 percent of the planet's surface never before seen at close range.
Approximately 98 percent of Mercury's surface now has been imaged by NASA spacecraft. After MESSENGER goes into orbit around Mercury, it will see the polar regions, which are the only unobserved areas of the planet.
"Although the area viewed for the first time by spacecraft was less than 350 miles across at the equator, the new images reminded us that Mercury continues to hold surprises," said Sean Solomon, principal investigator for the mission and director of the Department of Terrestrial Magnetism at the Carnegie Institution of Washington.
Many new features were revealed during the third flyby, including a region with a bright area surrounding an irregular depression, suspected to be volcanic in origin. Other images revealed a double-ring impact basin approximately 180 miles across. The basin is similar to a feature scientists call the Raditladi basin, which was viewed during the probe's first flyby of Mercury in January 2008.
"This double-ring basin, seen in detail for the first time, is remarkably well preserved," said Brett Denevi, a member of the probe's imaging team and a postdoctoral researcher at Arizona State University in Tempe. "One similarity to Raditladi is its age, which has been estimated to be approximately one billion years old. Such an age is quite young for an impact basin, because most basins are about four times older. The inner floor of this basin is even younger than the basin itself and differs in color from its surroundings. We may have found the youngest volcanic material on Mercury."
One of the spacecraft's instruments conducted its most extensive observations to date of Mercury's exosphere, or thin atmosphere, during this encounter. The flyby allowed for the first detailed scans over Mercury's north and south poles. The probe also has begun to reveal how Mercury's atmosphere varies with its distance from the sun.
"A striking illustration of what we call 'seasonal' effects in Mercury's exosphere is that the neutral sodium tail, so prominent in the first two flybys, is 10 to 20 times less intense in emission and significantly reduced in extent," says participating scientist Ron Vervack, of the Johns Hopkins University Applied Physics Laboratory, or APL, in Laurel, Md. "This difference is related to expected variations in solar radiation pressure as Mercury moves in its orbit and demonstrates why Mercury's exosphere is one of the most dynamic in the solar system."
The observations also show that calcium and magnesium exhibit different seasonal changes than sodium. Studying the seasonal changes in all exospheric constituents during the mission orbital phase will provide key information on the relative importance of the processes that generate, sustain, and modify Mercury's atmosphere.
The third flyby also revealed new information on the abundances of iron and titanium in Mercury's surface materials. Earlier Earth and spacecraft-based observations showed that Mercury's surface has a very low concentration of iron in silicate minerals, a result that led to the view that the planet's crust is generally low in iron.
"Now we know Mercury's surface has an average iron and titanium abundance that is higher than most of us expected, similar to some lunar mare basalts," says David Lawrence, an APL participating mission scientist.
The spacecraft has completed nearly three-quarters of its 4.9-billion-mile journey to enter orbit around Mercury. The full trip will include more than 15 trips around the sun. In addition to flying by Mercury, the spacecraft flew past Earth in August 2005 and Venus in October 2006 and June 2007.
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and after flybys of Earth, Venus, and Mercury will start a yearlong study of its target planet in March 2011. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
MESSENGER Gains Critical Gravity Assist for Mercury Orbital Observations - September 30, 2009
MESSENGER successfully flew by Mercury yesterday, gaining a critical gravity assist that will enable it to enter orbit about Mercury in 2011 and capturing images of five percent of the planet never before seen. With more than 90 percent of the planet's surface already imaged, MESSENGER's science team had drafted an ambitious observation campaign designed to tease out additional details from features uncovered during the first two flybys. But an unexpected signal loss prior to closest approach hampered those plans.
At approximately 5:55 p.m., the spacecraft passed by Mercury at an altitude of 142 miles and at a relative velocity of more than 12,000 miles per hour according to Doppler residual measurements logged just prior to the closest approach point. As the spacecraft approached the planet, MESSENGER's Wide Angle Camera captured this striking view, which shows portions of Mercury's surface that had remained unseen by spacecraft even after the three flybys by Mariner 10 in 1974 and 1975 and MESSENGER's two earlier flybys in 2008.
"This third and final flyby was MESSENGER's last opportunity to use the gravity of Mercury to meet the demands of the cruise trajectory without using the probe's limited supply of on-board propellant," says MESSENGER Mission Systems Engineer Eric Finnegan of the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Md.
A portion of the complicated encounter was executed in eclipse, when the spacecraft is in Mercury's shadow and the spacecraft – absent solar power – was to operate on its internal batteries for 18 minutes. Ten minutes after entering eclipse and four minutes prior to the closet approach point, the carrier signal from the spacecraft was lost, earlier than expected.
According to Finnegan, the spacecraft autonomously transitioned to a safe operating mode, which pauses the execution of the command load and "safes the instruments," while maintaining knowledge of its operational state and preserving all data on the solid-state recorder.
"We believe this mode transition was initiated by the on-board fault management system due to an unexpected configuration of the power system during eclipse," Finnegan says. MESSENGER was returned to operational mode at 12:30 a.m. with all systems reporting nominal operations. All on-board stored data were returned to the ground by early morning and are being analyzed to confirm the full sequence of events.
"Although the events did not transpire as planned, the primary purpose of the flyby, the gravity assist, appears to be completely successful," Finnegan adds. "Furthermore, all approach observing sequences have been captured, filling in additional area of previously unexplored terrain and further exploring the exosphere of Mercury."
"MESSENGER's mission operations and engineering teams deserve high commendation for their professional and efficient approach to last night's spacecraft safe-mode transition," says MESSENGER Principal Investigator Sean Solomon, of the Carnegie Institution of Washington. "They quickly diagnosed the initial problem, restored the spacecraft to its normal operating mode, and developed plans to recover as much of our post-encounter science observations as possible. Most importantly, we are on course to Mercury orbit insertion less than 18 months from now, so we know that we will be returning to Mercury and will be able to observe the innermost planet in exquisite detail."
Additional information and features from this encounter will be available online here. Be sure to check back frequently to see the latest released images and science results!
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and after flybys of Earth, Venus, and Mercury will start a yearlong study of its target planet in March 2011. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
MESSENGER Flyby of Mercury - September 29, 2009
Shortly before 5:55 p.m. EDT, MESSENGER skimmed 228 kilometers (141 miles) above the surface of Mercury in its third and final flyby of the planet. Radio signals received after the spacecraft emerged from behind the planet indicate that the spacecraft is operating nominally. Its instruments are now collecting images and other scientific measurements from the planet as it departs Mercury.
Tonight at 9:34 p.m., the spacecraft will turn its high-gain antenna back toward Earth to start down linking real-time telemetry. Downlink of the data stored onboard will start two hours later. The first images from the flyby will be released around 10:00 a.m. on September 30, 2009. Additional information and features from this encounter will be available online here. Be sure to check back frequently to see the latest released images and science results!
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and after flybys of Earth, Venus, and Mercury will start a yearlong study of its target planet in March 2011. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
Closest Approach Tomorrow! - September 28, 2009
MESSENGER's engineering and operations teams convened at the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Md., this morning to confirm the health and readiness of the spacecraft. "All spacecraft sub-systems and instruments reported nominal operations, indicating that MESSENGER was ready for its third encounter with Mercury," said MESSENGER Systems Engineer Eric Finnegan of APL.
At 10:28 a.m. the last bits of data from the spacecraft were received as it transitioned from high-gain downlink to beacon-only operations, turning towards the planet to start the approach tail-sweep sequence with the Mercury Atmospheric and Surface Composition Spectrometer instrument. This morning, the spacecraft returned this image, revealing some of the last areas of terrain not before seen at close range by spacecraft. Higher-resolution images of these areas will be obtained tomorrow when the spacecraft is closer to the planet.
For the next 30 hours, the spacecraft will take repetitive scans through Mercury's comet-like anti-sunward tail, pausing now and then to take a color image and a high-resolution mosaic of Mercury with the Mercury Dual Imaging System instrument.
The operations team will now prepare for the period of time after the closest approach point [tomorrow at 5:54:56 p.m.], approximately eight minutes after which the spacecraft will pass behind the planet and lose contact with Earth for a period of 51 minutes. "We will reestablish a high-rate data link with the spacecraft on Tuesday evening at 9:34 p.m., followed by playback of the data stored in the solid-state recorder starting at 11:39 p.m.," Finnegan adds.
"MESSENGER is now on its own to carry out the command sequence developed by the all of the dedicated engineers and scientist of the MESSENGER flight team," Finnegan says. "I look forward to the future scientific discoveries to be found in this new dataset."
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and after flybys of Earth, Venus, and Mercury will start a yearlong study of its target planet in March 2011. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
MESSENGER on Mercury's Doorstep - September 26, 2009
MESSENGER is approximately two days from its third encounter with Mercury. This will be the team's last opportunity to practice at Mercury before orbit insertion, so many of the instrument command sequences have been assembled to be similar to how they will operate during the orbital phase of the mission, which begins in March 2011.
MESSENGER's mission design and navigation teams met Friday at the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Md., to discuss the spacecraft's current trajectory to determine if a last-minute corrective maneuver would be needed. According to the latest trajectory determination from the navigation team, the spacecraft is very close to its intended flight path, and no correction is necessary.
"The spacecraft is less than 100 meters from the flyby altitude of 228 kilometers," said APL's Eric Finnegan, the MESSENGER Mission Systems Engineer. "Once again, the guidance, navigation, and control teams have been successful in passively solar sailing the spacecraft towards the targeted aim point, conserving propellant for potential future exploration."
On Friday afternoon, the deep space network antennas locked in on MESSENGER for continuous coverage. The command load for the encounter has been completed and verified. The first part of the command load is onboard the spacecraft and ready for execution starting tonight. The spacecraft will continue to gather approach images, while the operations team monitors the spacecraft. You can view the latest image online here.
The operations and engineering teams will gather in the operations center at APL early Monday morning to make one last assessment of the spacecraft before the closet approach observation sequence begins, rotating the probe away from the Earth to view once again the closest planet to the Sun.
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and after flybys of Earth, Venus, and Mercury will start a yearlong study of its target planet in March 2011. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
MESSENGER Prepares for Final Pass by Mercury - September 23, 2009
On September 29, 2009, the MESSENGER spacecraft will fly by Mercury for the third and final time, passing 141.7 miles above the planet's rocky surface for a final gravity assist that will enable it to enter orbit about Mercury in 2011. With more than 90 percent of the planet's surface already imaged, the team will turn its instruments during this flyby to specific features to uncover more information about the planet closest to the Sun.
"The first two flybys of Mercury revealed nearly half of the planet in detail for the first time," notes MESSENGER Principal Investigator Sean Solomon, of the Carnegie Institution of Washington. "During this third encounter, the MESSENGER camera will again image areas never before seen at close range, and we will obtain color images of other regions at resolutions superior to those of previous observations. Our other instruments will target interesting areas of the surface, atmosphere, and magnetosphere for detailed measurements designed to address questions raised by observations made during the earlier flybys."
Depending on the activity of the Sun, Solomon adds, MESSENGER might also view yet another distinct snapshot of how the planet interacts with conditions in interplanetary space driven by the behavior of our nearest star.
Peering through Mercury's Exosphere
The first two flybys provided an unprecedented glimpse into the structure of the planet's tenuous exosphere and the processes behind it. During this encounter, the Mercury Atmospheric and Surface Composition Spectrometer (MASCS) will again make high-spectral- and high-spatial-resolution measurements of Mercury's exosphere.
"Targeted scans of the planet's comet-like tail by the MASCS Ultraviolet and Visible Spectrometer will permit a search for temporal variability in both the sodium and calcium components," notes MASCS Instrument Scientist Noam Izenberg of the Johns Hopkins University Applied Physics Laboratory in Laurel, Md. "In addition, we will target the north- and south-polar regions for detailed observations of those species, and we will look for several new exospheric species."
A Few New Pictures
The Mercury Dual Imaging System (MDIS) will capture 1,559 pictures of the planet. "Using all 11 filters of the wide-angle camera, we are going to collect high-resolution, color images of scientifically interesting targets that we identified from the second flyby, and at the same time MASCS will observe those same targets," explains APL's Ralph McNutt, MESSENGER Project Scientist.
As MESSENGER approaches Mercury, MDIS's narrow-angle camera (NAC) will capture images of previously unseen terrain. Later, as the spacecraft departs, the NAC will take high-resolution images of the southern hemisphere that will be used to create a mosaic to complement the high-resolution, northern-hemisphere mosaic obtained during the second Mercury flyby.
Images captured eight days before and 21 days after the probe's closest approach to Mercury will allow MESSENGER scientists to create detailed phase curves of Mercury at multiple wavelengths, and searches will be conducted for possible satellites of Mercury as small as 100 meters in diameter.
Combing the Surface
Determining the composition of Mercury's surface is a major goal of the orbital phase of the mission, and during this flyby the instruments focused on compositional measurements will have a third opportunity to observe Mercury.
The MASCS sensors – both UVVS and the Visible and Infrared Spectrograph – will spend about 30 seconds on each of 11 targets, two at locations also targeted for photometry, focusing on end-member compositional characteristics identified during the second flyby. The X-Ray Spectrometer will once again look for X-ray fluorescence from surface elements, depending on the level of solar activity, and the Gamma-Ray Spectrometer will acquire more counting data from approximately the same region that it surveyed during the second flyby.
The Neutron Spectrometer will use two spacecraft maneuvers to provide better Doppler filtering of encountered neutron fluxes, including a 180° spacecraft roll on the night side (inbound) and a 45° roll on the dayside (outbound). The nightside maneuver will provide more information on the composition on the side of the planet away from that sampled during the first flyby, and the combination of dayside and night-side measurements will enable a test of the influence of planetary surface temperature on the thermal neutron fluxes, data important for properly interpreting the neutron fluxes to be measured during the orbital phase of the mission.
MESSENGER's third Mercury flyby will provide more data on the correlation between high-resolution topography and high-resolution images of Mercury. The Mercury Laser Altimeter (MLA) will range to Mercury's surface and make a topographic profile along the instrument ground track. A shift in the longitude of closest approach by 17° to the west and 3° north from the position of closest approach for the second flyby will allow the data from the third flyby to augment and complement those from the second flyby. In addition, the slower flyby speed (approximately 1.5 kilometers per second slower relative to the center of Mercury) will keep the trajectory closer to the planet longer.
"The data we gather will provide additional topography of surface features on Mercury for our ongoing studies of the morphology of craters and tectonic structures, such as thrust faults," says MLA Instrument Scientist Olivier Barnouin-Jha of APL. "It will also extend our equatorial view of Mercury's global shape and allow us to confirm the discovery made during the first and second flyby of MESSENGER that Mercury's equatorial region possesses a slightly elliptical shape."
Surprises about Mercury's Magnetic Field
The third Mercury encounter could reveal surprises about the planet's magnetic field, says MESSENGER Deputy Project Scientist Brian Anderson, of APL. "The first two flybys took the spacecraft over opposite sides of the planet – over the eastern hemisphere in January 2008 and the western side in October 2008," Anderson notes. "The third flyby will take it again over the planet's western hemisphere, and the observations will be used to refine the estimate of the planet's internal magnetic field."
Anderson says this flyby is the last opportunity to survey the magnetotail and magnetopause regions in the equatorial plane. "The contrast in the system's structure under different solar wind conditions already observed make it likely that the third flyby will yield new insights and perhaps more surprises regarding the dynamics of this smallest and most highly variable of the solar system's planetary magnetospheres," he adds.
As with the previous two flybys, the Magnetometer will record the magnetic field at the highest available observation rate of 20 vector magnetic field samples per second for a period of twelve hours centered on the time of closest approach. "This observing plan guarantees the highest possible science return from the encounter and will provide key observations to guide the magnetic field investigation plan for the prime orbital phase of the mission," Anderson says.
"This flyby will not only be our last close look at the equatorial regions of Mercury, it is our final planetary gravity assist, and it will be important for the entire encounter to be executed as planned," summarizes Solomon. "As enticing as these flybys have been for discovering some of Mercury's secrets, they are the hors d'oeurves to the mission's main course, observing Mercury from orbit for an entire year."
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and after flybys of Earth, Venus, and Mercury will start a yearlong study of its target planet in March 2011. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
Experience MESSENGER's Third Mercury Flyby Virtually - September 22, 2009
See Mercury through the "eyes" of MESSENGER's imagers with the Mercury Flyby Visualization Tool. This updated Web feature offers a unique opportunity to see simulated views of Mercury from MESSENGER's perspective, during approach, flyby, and departure, or in real-time (as the observations actually occur).
This tool combines one of the best available image maps of Mercury's surface with observation sequences for the Mercury Dual Imaging System (MDIS), Mercury Atmospheric and Surface Composition Spectrometer (MASCS), and Mercury Laser Altimeter (MLA). The map of Mercury's surface combines high-resolution image mosaics from the Mariner 10 spacecraft flybys of Mercury in 1974 and 1975 and images from MESSENGER's first two flybys of Mercury in January and October of last year.
There are many helpful tips available on the pages of this visualization tool. Pointing and clicking on any color bar will display the projection of each completed image mosaic on Mercury or show the end of the active MLA or MASCS observation. Information accompanying each simulated image includes the latitude and longitude of the point at the center of each image, the resolution in meters (or kilometers when farther from the planet) per pixel (picture element) at the image center, the altitude (how far the spacecraft is above Mercury's surface), and the time relative to closest approach.
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and after flybys of Earth, Venus, and Mercury will start a yearlong study of its target planet in March 2011. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
NASA TO PREVIEW MISSION'S THIRD FLIGHT PAST MERCURY - September 21, 2009
WASHINGTON -- NASA will host a media teleconference at 1 p.m. EDT on Wednesday, Sept. 23, to preview MESSENGER's third and final flyby of Mercury.
On Sept. 29, the spacecraft will swing less than 142 miles above the planet's rocky surface for a final gravity assist that will enable it to enter orbit around Mercury in March 2011. With more than 90 percent of the planet's surface imaged after the spacecraft's second flyby, the team will focus instruments on questions raised by the earlier flybys to advance our understanding of the planet closest to the Sun.
The briefing participants are:
- Anthony Carro, MESSENGER program executive, NASA Headquarters in Washington
- Eric J. Finnegan, mission systems engineer, Johns Hopkins University Applied Physics Laboratory in Laurel, Md.
- Noam R. Izenberg, Mercury Atmospheric and Surface Composition Spectrometer instrument scientist, Johns Hopkins University Applied Physics Laboratory
- Sean C. Solomon, principal investigator, Carnegie Institution of Washington
To participate in the teleconference, reporters should e-mail Dwayne Brown at dwayne.c.brown@nasa.gov for dial-in and passcode information.
Audio of the teleconference will be streamed live at:
http://www.nasa.gov/newsaudio
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and after flybys of Earth, Venus, and Mercury will start a yearlong study of its target planet in March 2011. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
MESSENGER Team Prepares for Third Flyby, Rehearses for Orbital Operations - September 16, 2009
In less than two weeks, on September 29, MESSENGER will fly by Mercury for the third and final time, a maneuver key to placing the probe on a trajectory that will enable its March 2011 insertion into orbit about Mercury. Even as the team readies for this critical event, a parallel effort has long been underway to prepare MESSENGER for the main event.
Since January, the team has been staging orbital operations rehearsal tests, called week-in-the-life (WITL) tests, to try out the new procedures and software being developed for the Mercury orbital mission. Next month, they will wrap up the second such test, and the results of these exercises are proving pivotal to the team's plan.
"Because no spacecraft has orbited the planet Mercury before, we do not have any direct experience planning and scheduling science observations in such an environment," explains Alice Berman, MESSENGER's Payload Operations Manager. "Therefore, a comprehensive orbital operations readiness plan is underway to ensure that the mission's full science success criteria can be met by the time that the nominal mission ends on 17 March 2012. The WITL tests, meant to simulate several realistic weeks of orbital operations, are an integral part of this overall readiness plan."
Between 2009 and 2010, the team will run at least seven WITLs covering different weeks and orbital conditions. "It's critical to test as many different observing scenarios and orbital conditions that will occur during the orbital mission as possible," Berman says.
The first WITL test ran from January to April. The team chose to rehearse the planning and scheduling for a week in mid-October 2011, when the level of instrument commanding is not extremely demanding. The focus of WITL-1 was primarily on new procedures and software that had recently been developed. "We wanted to walk through all the processing steps of preparing a weekly command load, with careful attention to the newly developing software tools," Berman recounts.
At an all-day workshop in February, the instrument teams worked through the required steps for preparing and delivering their WITL-1 instrument sequences to the mission operations team. The mission operations team then built the spacecraft command load – adding the necessary spacecraft commanding (e.g., solar array commanding, spacecraft downlinks) – and ran it on the MESSENGER hardware simulator. With that done, the mission operations and science operations teams reviewed the results.
A debriefing meeting was held in April to review the success of the test and gather the issues to be addressed and lessons learned prior to starting the next rehearsal test. "We learned that we need to have an extremely easy and efficient process, because we must start a new command load each week," Berman explains. "We need a way to automatically keep track of status and approvals and to notify team members when their attention or action is needed. We found a project management software called JIRA that will help us do all this. We learned a lot about what our current tools can do (and what they cannot), and we are prioritizing the required software fixes and enhancements now."
The second WITL test began in July 2009 and will be completed in October. "In addition to testing the improved the orbital planning processes and software, WITL-2 is focusing on a different timeframe of the orbital mission, so that different instrument and spacecraft components will be tested," Berman says. "Right now the mission operations team is building the WITL-2 integrated command load, and then it will be tested on the MESSENGER hardware simulator."
The remaining WITL tests will be conducted in 2010, and the team is currently developing the schedule and scope of these tests. "In 2010, the WITL tests will overlap in time so that the teams can exercise the process of working on more than one weekly command load at one time," Berman notes. "We will carefully assess what works well and what does not, and we will update our processes and software tools with the lessons learned from each WITL test."
"Once in orbit, our near-term scheduling strategy will be to prepare and upload a new command load (containing both instrument and spacecraft instructions) once per week," Berman adds. "This work will require the close coordination of both the science and mission operations teams. We believe that it will take approximately three weeks to prepare each command load, so the science and mission operations teams will be working on more than one command load at any given time."
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and after flybys of Earth, Venus, and Mercury will start a yearlong study of its target planet in March 2011. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
Upcoming Mercury Encounter Presents New Opportunities for Magnetometer - August 20, 2009
On September 29, the MESSENGER spacecraft will pass by Mercury for the third time, flying 141.7 miles above the planet's rocky surface for a final gravity assist that will enable it to enter orbit about Mercury in 2011. This encounter will also provide new observational opportunities for MESSENGER's Magnetometer, designed to determine the structure and origin of Mercury's intrinsic magnetic field.
The comparison of magnetosphere observations from MESSENGER's first flyby in January 2008 with data from the probe's second pass in October 2008 provided key new insight into the nature of the planet's internal magnetic field and revealed new features of Mercury's magnetosphere, explains Brian Anderson, of the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Md.
"MESSENGER's first flyby of Mercury and Mariner 10's encounters with the planet provided data only from Mercury's eastern hemisphere," says Anderson, MESSENGER's Deputy Project Scientist. "The October 2008 flyby provided the first measurements from Mercury's western hemisphere, and scientists learned that the planet's magnetic field is highly symmetric. This finding is significant for the planet's internal field because it implies that the dipole is even more closely aligned with the planet's rotation axis than we could conclude before the second flyby."
The probe's third flyby of Mercury next month will take it again over the planet's western hemisphere, and the observations will be used to refine the estimate of the planetary magnetic field, Anderson explains.
"The previous flybys yielded significant insight into the dynamics of Mercury's magnetosphere and its boundaries," Anderson says. "During the second flyby a plasmoid and a series of traveling compression regions were observed in Mercury's magnetotail, and a large flux transfer event was observed at the dayside magnetopause. These observations proved that the solar wind interaction, under the right circumstances, can drive intense magnetic reconnection at rates 10 times the rates observed at Earth."
The behavior during the second flyby was markedly different from that found in the first flyby, demonstrating the profound influence of the solar wind environment on Mercury's magnetosphere. "The third flyby is the last opportunity to survey the magnetotail and magnetopause regions in the equatorial plane, and the contrast in the system's structure under different solar wind conditions already observed make it likely that the third flyby will yield new insights and perhaps more surprises for the dynamics of this smallest and most highly variable of the solar system's planetary magnetospheres," Anderson says.
As with the previous two flybys, the Magnetometer will record the magnetic field at the highest available observation rate of 20 vector magnetic field samples per second for a period of twelve hours centered on the time of closest approach. "This observing plan guarantees the highest possible science return from the encounter and will provide key observations to guide the magnetic field investigation plan for the prime orbital phase of the mission," Anderson says.
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and after flybys of Earth, Venus, and Mercury will start a yearlong study of its target planet in March 2011. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
MESSENGER Mission Passes Five-Year Mark - August 3, 2009
It's been five years since MESSENGER was launched atop a Delta II rocket on August 3, 2004, and they have been busy years. It has been a long journey, says MESSENGER Mission Operations Manager Andy Calloway, "not just in distance travelled – just over 3.5 billion miles so far – but also in terms of significant milestones and accomplishments."
MESSENGER has executed five planetary flybys – one of Earth on August 2, 2005; two of Venus, on October 24, 2006, and June 5, 2007; and two of Mercury, on January 14, 2008, and October 6, 2008. "These were not merely gravity assists, but also major science data collection endeavors that required months of detailed planning," says Calloway of the Johns Hopkins University Applied Physics Laboratory (APL).
The probe has completed four major deep-space maneuvers (DSMs) and 12 trajectory-correction maneuvers, and mission controllers have been able to forgo six additional planned course corrections by using MESSENGER's solar panels creatively, harnessing solar radiation pressure to adjust the spacecraft's trajectory.
"Because of the implementation of solar sailing, the MESSENGER team has not used propellant to correct the cruise trajectory of the spacecraft since December 19, 2007, in advance of the first Mercury flyby," says MESSENGER Mission Systems Engineer Eric Finnegan, of APL. He credits a solar sailing team of engineers – Ken Williams in navigation, Jim McAdams in trajectory design, and Dan O'Shaughnessy in guidance and control – "for increasing mission performance while lowering mission risk by making this technique operational."
Over the years, MESSENGER's circuitous journey has presented opportunities within challenges. "We've been through periodic extended communication outages as the spacecraft travels on the far side of the Sun from Earth during superior solar conjunctions and frequent close passages by the Sun during perihelion crossings," Calloway says. "But MESSENGER has traveled as close to the Sun as only three tenths of the Earth-Sun distance during these crossings, providing valuable information and experience in preparation for orbital operations, which begin following the critical Mercury orbit insertion maneuver in 2011."
In addition to nine major instrument software loads during these five years (with two more planned this month), the third main processor flight software update of the mission was successfully completed on July 14, 2009.
"This new software significantly increases the spacecraft's capabilities for the upcoming orbital phase," Calloway says. "These processor loads require months of testing, and then once the software is loaded to the spacecraft, the processor has to be rebooted for it to take effect. This rebooting results in a transition to a Sun-safe rotisserie mode in which the spacecraft transmits a beacon signal as it rotates slowly every 3.5 hours. Operators in the control center monitored the signal as it briefly swept through the ground station's field of view one rotation after the reboot, and seven hours later they sent a command with precise timing to halt the rotation and begin restoring the spacecraft to its nominal operational mode."
More than 90% of Mercury's surface has now been imaged after MESSENGER's flybys, including territory never seen before by spacecraft, and planning is in full swing for the orbital phase of the mission. Up next is a third pass by Mercury on September 29, 2009, a fifth DSM on November 24, 2009, and then on March 18, 2011, MESSENGER will become the first spacecraft to enter into orbit around the innermost planet.
"When MESSENGER launched five years ago, even our first encounter with Mercury seemed far off," recounts MESSENGER Principal Investigator Sean Solomon, of the Carnegie Institution of Washington. "Our first two Mercury flybys last year produced an explosion of new and exciting observations, and our cruise through the inner Solar System as of this important anniversary is more than 75% complete. The entire MESSENGER team is eagerly awaiting the first observations of Mercury from orbit."
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and after flybys of Earth, Venus, and Mercury will start a yearlong study of its target planet in March 2011. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
Sixteen Craters on Mercury Have New Names - July 15, 2009
The International Astronomical Union (IAU) recently approved a proposal from the MESSENGER Science Team to confer names on 16 impact craters on Mercury. The newly named craters were imaged during the mission's first two flybys of Mercury in January and October last year.
In the time since the flybys, MESSENGER team members have been analyzing the images and other data and preparing papers for publication in scientific journals. "Having names for these features will help to improve communication among those studying the planet's geology," says MESSENGER Participating Scientist Dave Blewett, of the Johns Hopkins University Applied Physics Laboratory, in Laurel, Md.
The IAU has been the arbiter of planetary and satellite nomenclature since its inception in 1919. In keeping with the established naming theme for craters on Mercury, all of the craters are named after famous deceased artists, musicians, or authors. The newly named craters include:
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and after flybys of Earth, Venus, and Mercury will start a yearlong study of its target planet in March 2011. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
Three New Co-Investigators Added to MESSENGER Team - June 26, 2009
Brian Anderson, Louise Prockter, and Thomas Zurbuchen have been appointed MESSENGER Co-Investigators by NASA Science Mission Directorate Associate Administrator Edward Weiler.
"Each of these individuals has served admirably as MESSENGER Instrument Scientists, and each has led an important aspect of the analysis and interpretation of MESSENGER observations from the first two Mercury flybys," notes MESSENGER Principal Investigator Sean Solomon.
As a MESSENGER Deputy Project Scientist, Anderson, of the Johns Hopkins University Applied Physics Laboratory (APL), oversees the orbital operations planning to ensure that observations from all of the instruments are coordinated to meet the mission objectives. He formerly served as the Magnotometer Instrument Scientist. In his additional role as Co-Investigator, Anderson will provide scientific direction to the operation of the Magnetometer instrument in orbit, including in-flight calibration, data validation, science product generation, and coordination with the operation of and data returned from other instruments closely related to investigation of Mercury's magnetic field. In addition, he will lead aspects of the science analysis of data from the Magnetometer and other instruments in understanding Mercury's internal magnetic field and magnetosphere, particularly efforts to identify and quantify the magnetospheric contributions to the observations so as to recover the structure of Mercury's internal magnetic field to the highest fidelity possible.
Prockter, also of APL, serves as the Instrument Scientist for the Mercury Dual Imaging System (MDIS). In her new role as Co-Investigator, she will provide scientific direction to the operation of MDIS in Mercury orbit, including instrument calibration, data validation, science product generation, and coordination with the operation of and data returned from other instruments related to observations of Mercury's surface. In addition, she will lead aspects of the science analysis of MDIS observations to improve our understanding of the geological evolution of Mercury, particularly the study of impact melting during the formation of large craters and basins on Mercury and the contribution of impact melts to smooth plains deposits.
Zurbuchen, of the University of Michigan, is the Instrument Scientist for the Energetic Particle and Plasma Spectrometer. As a Co-Investigator, he will provide scientific direction to the operation of the Fast Imaging Plasma Spectrometer (FIPS) sensor in orbit, including calibration, data validation, science product generation, and coordination with the operation of and data returned from other instruments sensitive to the exosphere and magnetosphere. He will also lead aspects of the science analysis of data from FIPS and other instruments in understanding Mercury's charged particle environment, particularly the analysis of the distribution of plasma ions in Mercury's vicinity and the implications of their energies and compositions for magnetosphere-solar wind interaction at Mercury.
"MESSENGER is one of the most important things I am working on and has accompanied me and my team for over 10 years," Zurbuchen says. "We look forward to the next 10 years of science data and breakthroughs that will come from MESSENGER, and particularly from the Fast Imaging Plasma Spectrometer."
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and after flybys of Earth, Venus, and Mercury will start a yearlong study of its target planet in March 2011. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
MESSENGER Co-Investigator Stanton J. Peale, a professor emeritus renowned for his work in planetary science and astrophysics at University of California, Santa Barbara, was among the 72 new members elected to the National Academy of Sciences. The election was held April 28 during the business session of the 146th annual meeting of the Academy. Those elected bring the total number of active members to 2,150, now including four members of the MESSENGER Science Team.
Peale is a leading expert on planetary dynamics. He developed the technique by which MESSENGER will measure the size and state of Mercury's core, and he will lead the interpretation of Mercury Laser Altimeter (MLA) measurements of Mercury's rotation and physical libration.
His theory for Mercury's forced libration, equivalent to small variations in Mercury's spin rate, was recently utilized to interpret Earth-based radar measurements of Mercury's motions. Those observations can be explained only if Mercury's core is at least partially molten, a finding that has helped scientists better understand Mercury's thermal history and the generation of the planet's intrinsic magnetic field.
As a member of the Academy, Peale will help advise the federal government on science and technology issues. Additional information about the Academy and its members is available online at http://www.nasonline.org.
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and after flybys of Earth, Venus, and Mercury will start a yearlong study of its target planet in March 2011. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
MESSENGER Reveals Mercury as a Dynamic Planet - April 30, 2009
Analyses of data from the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft's second flyby of Mercury in October 2008 show that the planet's atmosphere, magnetosphere, and geological past are all characterized by much greater levels of activity than scientists first suspected.
On October 6, 2008, the probe flew by Mercury for the second time, capturing more than 1,200 high-resolution and color images of the planet unveiling another 30 percent of Mercury's surface that had never before been seen by spacecraft and gathering essential data for planning the remainder of the mission.
"MESSENGER's second Mercury flyby provided a number of new findings," says MESSENGER Principal Investigator Sean Solomon at the Carnegie Institution of Washington. "One of the biggest surprises was how strongly the planet's magnetospheric dynamics changed from what we saw during the first Mercury flyby in January 2008. Another was the discovery of a large and unusually well preserved impact basin that was the focus for concentrated volcanic and deformational activity. The first detection of magnesium in Mercury's exosphere and neutral tail provides confirmation that magnesium is an important constituent of Mercury's surface materials. And our nearly global imaging coverage of the surface after this flyby has given us fresh insight into how the planet's crust was formed."
These findings are reported in four papers published in the May 1 issue of Science magazine.
An Abundance of Magnesium
The probe's Mercury Atmospheric and Surface Composition Spectrometer, or MASCS, detected significant amounts of magnesium in the planet's atmosphere, reports William McClintock of the University of Colorado at Boulder's Laboratory for Atmospheric and Space Physics. "Detecting magnesium was not too surprising, but seeing it in the amounts and distribution we recorded was unexpected," said McClintock, a MESSENGER co-investigator and lead author of one of the four papers. "This is an example of the kind of individual discoveries that the MESSENGER team will piece together to give us a new picture of how the planet formed and evolved."
The instrument also measured other exospheric constituents during the October 6 flyby, including calcium and sodium, and he suspects that additional metallic elements from the surface including aluminum, iron, and silicon also contribute to the exosphere.
Radically Different Magnetosphere
MESSENGER observed a radically different magnetosphere at Mercury during its second flyby, compared with its earlier January 14 encounter, writes MESSENGER co-investigator James Slavin, of the NASA Goddard Space Flight Center, lead author of another paper. "During the first flyby, MESSENGER entered through the dusk side of the magnetic tail, measuring relatively calm dipole-like magnetic fields closer to the planet, and then exited the magnetosphere near dawn," Slavin says. "Important discoveries were made, but scientists didn't detect any dynamic features, other than some Kelvin-Helmholtz waves along its outer boundary, the magnetopause."
But the second flyby was a totally different situation, he says. "MESSENGER measured large magnetic flux leakage through the dayside magnetopause, about a factor of 10 greater than even what is observed at the Earth during its most active intervals. The high rate of solar wind energy input was evident in the great amplitude of the plasma waves and the large magnetic structures measured by the Magnetometer throughout the encounter."
The magnetospheric variability observed thus far by MESSENGER supports the hypothesis that the great day-to-day changes in Mercury's atmosphere may be due to changes in the shielding provided by the magnetosphere.
The Rembrandt Basin
One of the most exciting results of MESSENGER's second flyby of Mercury is the discovery of a previously unknown large impact basin. The Rembrandt basin is more than 700 kilometers (430 miles) in diameter and if formed on the east coast of the United States would span the distance between Washington, D.C., and Boston.
The Rembrandt basin formed about 3.9 billion years ago, near the end of the period of heavy bombardment of the inner Solar System, suggests MESSENGER Participating Scientist Thomas Watters, lead author of another of the papers. Although ancient, the Rembrandt basin is younger than most other known impact basins on Mercury.
"This is the first time we've seen terrain exposed on the floor of an impact basin on Mercury that is preserved from when it formed" says Watters. "Landforms such as those revealed on the floor of Rembrandt are usually completely buried by volcanic flows."
Mercury's Crustal Evolution
Just over a year ago, half of Mercury was unknown. Globes of the planet were blank on one side. With image data from MESSENGER, scientists have now seen 90 percent of the planet's surface at high resolution and can start to assess what this global picture is telling us about the history of the planet's crustal evolution, says Brett Denevi, a MESSENGER team member at Arizona State University and lead author of one of the papers.
"After mapping the surface, we see that approximately 40 percent is covered by smooth plains," she says. "Many of these smooth plains are interpreted to be of volcanic origin, and they are globally distributed (in contrast with the Moon, which has a nearside/farside asymmetry in the abundance of volcanic plains). But we haven't yet seen evidence for a feldspar-rich crust, which makes up the majority of the lunar highlands and is thought to have formed by flotation during the cooling of an early lunar magma ocean. Instead, much of Mercury's crust may have formed through repeated volcanic eruptions in a manner more similar to the crust of Mars than to that of the Moon."
Scientists continue to examine data from the first two flybys and are preparing to gather even more information from a third flyby of the planet on September 29, 2009.
"The third Mercury flyby is our final 'dress rehearsal' for the main performance of our mission: insertion of our probe into orbit around Mercury in March 2011 and the continuous collection of information about the planet and its environment for one year," adds Solomon. "The orbital phase of our mission will be like staging two flybys per day. We'll be drinking from a fire hose of new data, but at least we'll never be thirsty. Mercury has been coy in revealing its secrets slowly so far, but in less than two years the innermost planet will become a close friend."
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and after flybys of Earth, Venus, and Mercury will start a yearlong study of its target planet in March 2011. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
MESSENGER Team to Receive National Space Club Award - April 17, 2009
The National Space Club will award the MESSENGER team its Nelson P. Jackson Aerospace Award this evening at the 52nd annual Dr. Robert H. Goddard Memorial Dinner in Washington, D.C. The award, named in honor of the National Space Club's founder and past president, is presented annually to recognize exceptional teamwork between government and industry in the missile, aircraft, and space fields.
"It is very heartening that the National Space Club has recognized the accomplishments to date of the MESSENGER spacecraft," offers MESSENGER Principal Investigator Sean Solomon. "A list of past recipients of the Jackson Award includes some very impressive space missions, so we are deeply honored to be numbered among that group. It is particularly fitting that this award is given for teamwork, because MESSENGER is very much the product of the cooperative efforts of an exceptional group of engineers, managers, and scientists from academic laboratories, industry, and NASA. Everyone on the MESSENGER team is being acknowledged for those efforts tonight."
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and after flybys of Earth, Venus, and Mercury will start a yearlong study of its target planet in March 2011. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
MESSENGER Team Remembers Dr. Mario H. Acuña - March 20, 2009
Mario H. Acuña, a senior astrophysicist at NASA Goddard Space Flight Center and Co-Investigator on the MESSENGER mission, died on March 5, 2009, after a long battle against multiple myeloma. During his four decades at NASA, he played a critical role in many NASA endeavors, serving as principal investigator or key developer of experiments flown on more than 30 missions to every planet in the solar system, as well as the Sun.
Acuña had been involved in the MESSENGER from its inception, 13 years ago. "He became an enthusiastic participant as soon as I mentioned MESSENGER to him, when it was just an idea without an acronym," notes Stamatios M. Krimigis, chair of MESSENGER's Atmosphere and Magnetosphere Group. "His deep technical knowledge and scientific insight, coupled with his absolute honesty and integrity made him an indispensable member of any technical review and a critical player when hard decisions had to be made."
Acuña contributed to the development of the Magnetometer (MAG) and the analysis of MAG observations from MESSENGER's first two flybys of Mercury. "He brought with him a wealth of experience that was truly irreplaceable," says Brian Anderson, MESSENGER's Deputy Project Scientist. "He was a fountain of knowledge about anything concerning magnetic fields and magnetometer instrumentation. His breadth of understanding was astonishing. From arcane properties of materials to the intricacies of the electronics design in his instruments, you could count on Mario to have gems of wisdom to offer. To work with Mario on any project was to learn from him. We did our best to be good students, but it will be difficult knowing that we can no longer pick up the phone when we feel the need of his advice."
Born in Córdoba, Argentina, in 1940, Acuña also brought with him a certain "Argentinean spice," Anderson says. "Whether it was a novel scientific interpretation that he was determined to get you to take seriously or an engineering detail for calibrating or operating the magnetometer, you always knew where Mario stood, and he was anything but bashful about making his point. Debate was something he loved - the hotter the better! But you could always catch a twinkle in his eye and knew that his heart was with you, and if he was passionate it was because he felt strongly about science and exploration."
MESSENGER Project Scientist Ralph McNutt knew Acuña since the 1970s, having worked with him on the Voyager 1 mission. "Here you had this brilliant research scientist, but he never had 'airs' about him; no pretentions," McNutt says.
Richard Starr, instrument scientist for the MESSENGER X-Ray Spectrometer, worked with Acuña on several projects, "but the one that stands out the most for me is our collaboration on the X-Ray Spectrometer for the Clark mission."
Originally scheduled for launch in mid-1996, the Clark spacecraft was to scan Earth with a sophisticated high-resolution camera to provide environmental data. "The Clark mission never launched," Starr says. "It was canceled by NASA due to cost overruns. But for me personally it was still a great success because of what I learned and accomplished working with Mario. We delivered our instrument on time and on budget."
Starr also points out that Acuña bridged the gap between scientist and engineer. "For him there really was no difference; it was all part of the same job," he said. "At Goddard we have the John C. Lindsay Memorial Award for Space Science and the Moe I. Schneebaum Memorial Award for Engineering. As far as I know, Mario is the only person to have won both."
MESSENGER will enter Mercury's orbit in less than two years, on March 18, 2011. "While the journey will continue, it won't be nearly as enjoyable without Mario," Anderson says. "Perhaps his memory is best served by recalling his devotion to inquiry and advancing human understanding and making sure that the science we do with the MESSENGER magnetometer is up to the Mario Acuña standard."
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and after flybys of Earth, Venus, and Mercury will start a yearlong study of its target planet in March 2011. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
MESSENGER Continues Hunt for Ever-Elusive Vulcanoids - February 9, 2009
MESSENGER reaches its orbital perihelion today and passes within 0.31 astronomical units (AU) of the Sun (one AU is nearly 150 million kilometers or 93 million miles). The mission's imaging team is taking advantage of the probe's proximity to the fiery sphere to continue their search for vulcanoids – small, rocky asteroids that have been postulated to circle the Sun in stable orbits inside the orbit of Mercury.
Vulcanoids are named after Vulcan, a planet once proposed to explain unusual motions in Mercury's orbit. Scientists have long suspected that these small, faint "space rocks" exist. There is a gravitationally stable region between the orbit of Mercury and the Sun, which means that any objects that originally formed there could have remained for billions of years and might still be there today. All other such regions in the solar system are occupied by some type of debris (e.g., Trojan asteroids at stable points along the orbits of Jupiter and Neptune and Kuiper Belt objects near and beyond the orbit of Pluto).
The so-called vulcanoid region between the orbit of Mercury and the Sun is the main gravitationally stable region that is not known to be occupied. The region is, however, the most difficult to observe. Any vulcanoids would be difficult to detect from Earth because of the strong glare of the Sun. Previous vulcanoid searches have revealed no bodies larger than 60 kilometers in diameter. But MESSENGER's travels in near-Mercury space enable a search for vulcanoids from a vantage never before attempted, says MESSENGER Science Team Member Clark Chapman, who is spearheading the team's search along with his associate, William Merline.
"With MESSENGER, we can search for vulcanoids as small as 15 kilometers across," said Chapman, a senior scientist at the Southwest Research Institute in Boulder, Colorado. Between February 7 and 11, the wide-angle camera of MESSENGER's Mercury Dual Imaging System will have snapped 256 images in the areas east and west of the Sun. Because of the danger of the Sun's glare, the camera will have to peek just past the probe's sunshade to capture images.
"We are making the same observations on each day," MESSENGER team member Nancy Chabot explained. "This cadence will allow us to reject cosmic rays and to distinguish, by its motion, the class of each object imaged" (e.g., vulcanoid vs. near- or inner-Earth asteroid).
The team carried out a similar imaging campaign over a nine-day period in June 2008, capturing 240 images of the outer portions of the would-be vulcanoid belt. "This sequence was designed to refine our observing techniques, assess limiting magnitudes, verify detectability of known objects, and make an initial search," Chapman explained.
"Vulcanoids, should they be found, may provide scientists with insights into the conditions prevalent in the early solar system," Chapman said. "In particular, if they exist or once existed, they would represent an additional population of impactors that would have cratered no other planet but Mercury, implying that the geological processes on Mercury have happened more recently than we would calculate if we assumed that Mercury's craters formed at rates equivalent to cratering on the Moon and Mars."
If vulcanoids are found not to exist, then we could be more confident that most of Mercury's volcanic plains formed billions of years ago, as on the Moon, according to Chapman. The absence of vulcanoids would also focus scientists' thinking on why vulcanoids never formed or, if they did form, why they are no longer there.
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and after flybys of Earth, Venus, and Mercury will start a yearlong study of its target planet in March 2011. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
MESSENGER Approaches Three Billion Miles, Enters Fourth Solar Conjunction - December 23, 2008
On December 26, the MESSENGER spacecraft will have traveled three billion miles since its launch, marking somewhat more than 60 percent of the probe's journey toward its destination to be inserted into orbit about Mercury.
"That MESSENGER's odometer reading has reached another major milestone reminds us of the long and complex route that our spacecraft must follow," offers Principal Investigator Sean Solomon, of the Carnegie Institution of Washington. "The year now ending has seen the first two spacecraft flybys of the innermost planet in more than three decades, encounters that have yielded a rich lode of new observations. The journey is far from over, but MESSENGER has a skilled team to guide it the rest of the way."
Mercury orbits deep within the Sun's gravity well. So, even though the planet can be as close as 82 million kilometers (51 million miles) from Earth, getting the probe into orbit around Mercury depends on an innovative trajectory using the gravity of Earth, Venus, and Mercury itself to slow and shape the probe's descent into the inner solar system. On its 4.9 billion-mile journey to becoming the first spacecraft to orbit the planet Mercury, MESSENGER has flown by Earth once, Venus twice, and Mercury twice. Still to come is one more flyby of Mercury in late September 2009.
Today the spacecraft entered its fourth superior solar conjunction of the mission, placing it on the opposite side of the Sun from Earth. The Sun-Earth-probe angle will be between 2° and 3° until January 6, 2009, so during the next two weeks there will be no communication with the spacecraft.
To support the conjunction period, the MESSENGER team performed several activities to prepare the spacecraft and keep it safe, explains MESSENGER Mission Operations Manager Andy Calloway. Examples include extension of the onboard command detection timer and inclusion of attitude alternations to avoid an autonomous propulsive burn to unload spacecraft angular momentum. In addition, all instruments have been turned off except for the Gamma-Ray Spectrometer sensor, which will remain in a maintenance mode to control closely the temperature of its cryogenic cooler.
"The team will gather for a spacecraft health assessment on the first contact after the conjunction, and then the payload will be powered on again, timers will be restored, and nominal operations will resume," says Calloway, of the Johns Hopkins University Applied Physics Laboratory in Laurel, Md. "The next superior solar conjunction lasts only five days – from June 6 to June 10 – and will therefore not require such extensive preparations." The next long conjunction spans about two weeks beginning on November 2, 2009.
The MESSENGER spacecraft is a little more than two years from reaching its final destination, but the mission Science Team has been collecting data and sharing it with the larger scientific community.
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and after flybys of Earth, Venus, and Mercury will start a yearlong study of its target planet in March 2011. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
MESSENGER Team to Present New Mercury Science Results at AGU Fall Meeting - December 12, 2008
Members of the MESSENGER science team will present a range of new findings from the spacecraft's studies of the planet Mercury during the American Geophysical Union (AGU) Fall Meeting next week in San Francisco.
"The principal goal of the MESSENGER mission is to gather global observations of Mercury from orbit about the planet, beginning in 2011, but our first two flybys produced a wonderful abundance of new information about the least known of our sister planets," says MESSENGER Principal Investigator Sean Solomon of the Carnegie Institution of Washington. "The AGU Fall Meeting is the first opportunity for most science team members to share results from the second Mercury flyby with our scientific community colleagues."
MESSENGER scientists will present 44 papers – some in a webcast session – that span the broad diversity of planetary phenomena observed by MESSENGER's instruments when the probe flew past Mercury in January and October 2008. Some of these papers cover discoveries regarding the environment around Mercury, such as how solar-derived particles originate and blast off into space.
"Flying that close to the Sun, MESSENGER gave us our best look yet at several solar phenomena," says MESSENGER Project Scientist Ralph McNutt, of the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Md. "We're detecting dust and other particles near the Sun and gaining insight on neutron behavior in this dynamic environment. Not only are we learning more about how these materials speed toward Earth and beyond, but we're learning about the conditions that MESSENGER will encounter when it becomes the first spacecraft to orbit the innermost planet."
William Feldman of the Planetary Science Institute will present new analyses that add to our knowledge of the dynamics of solar flares. Nuclear interactions in solar flares can produce energetic neutrons, and these neutrons are important keys to understanding flare processes. However, free neutrons have lifetimes of only about 15 minutes and decay into protons, electrons, and antineutrinos. Only the fastest (highest-energy) neutrons from solar flares can therefore reach Earth before they decay.
MESSENGER, at about two times closer to the Sun than Earth, made the first observations of lower-energy (less than 10 million electron volts) solar neutrons from a modest-sized solar flare on December 31, 2007.The neutrons from this New Year's Eve flare continued to be observed for many hours, unlike the optical emissions from the flare. The duration of neutron production implies that the acceleration and storage of atomic particles in the solar corona continued for a long time.
"The fact that this time is considerably longer than the mean lifetime of a neutron indicates that neutrons at the Sun must have been continuously produced," Feldman explains. "The extended production of neutrons means that a large region near the Sun will be populated by neutron-decay protons, which can seed the later acceleration of protons by coronal mass ejection-driven shock waves that can produce a dangerous radiation environment for all satellites in interplanetary and planetary space."
An extended source of heavy ions and molecules was discovered using data from MESSENGER's novel Fast Imaging Plasma Spectrometer by taking ion composition measurements prior to and following MESSENGER's two Mercury flybys. The University of Michigan's George Gloeckler will report on the interactions of the solar wind with a distributed "inner source" of dust and other material orbiting the Sun.
"The existence of an inner source was inferred from earlier observations of energetic singly-charged carbon with the Solar Wind Ion Composition Spectrometer on Ulysses at much larger distances from the Sun," Gloeckler says. "Being closer to this inner source with MESSENGER, we now find not only carbon and water-group ions but also many other elements and molecules with masses as high as 130 that of a proton, including Na, Mg, K, Ca, and Fe compounds." Gloeckler speculates that this inner source of material includes debris from Sun-grazing comets, dust particles, and possibly larger objects orbiting the Sun.
MESSENGER's Mercury flyby observations also revealed noteworthy differences in the planet's magnetosphere between January and October and – coupled with ground-based observations – have led to new discoveries about the planet's exosphere. James Slavin of NASA's Goddard Space Flight Center will present MESSENGER measurements indicating that a form of strong interaction between interplanetary and planetary magnetic fields, termed "reconnection," is approximately three times as effective in channeling solar wind energy into Mercury's near-space environment as it is at Earth.
Reconnection is known to control the rate of energy transfer from the solar wind to planetary magnetospheres. "The intensity of this energy input greatly influences the frequency and duration of the magnetic storms that accelerate charged particles, which modify planetary surfaces, produce aurorae in planetary atmospheres, and can affect spacecraft," Slavin says. "This MESSENGER result supports the theories that predict such an increase in the rate of reconnection as a result of the increase in the strength of the interplanetary magnetic field at Mercury's distance from the Sun. The high rate of energy input into Mercury's magnetic field in the MESSENGER measurements means that magnetic storms, which have durations of weeks at Jupiter and Saturn and an hour at the Earth, are expected to be much more frequent at Mercury but to last for only a few minutes."
During MESSENGER's first Mercury flyby in January, and again three weeks after the second flyby in October, ground-based observations of emission from the planet's sodium exosphere were obtained at the McMath-Pierce Solar Telescope at Kitt Peak, Arizona, concurrently with observations from the probe's Ultraviolet and Visible Spectrometer (UVVS) on the Mercury Atmospheric and Surface Composition Spectrometer instrument.
The sodium exosphere has been observed via ground-based observations to be highly asymmetric and variable, at times to be peaked near the sub-solar point and at other times peaked at one or both poles. MESSENGER's UVVS observations of the sodium tail revealed a north-south asymmetry near the planet during the first flyby. The cause of the high-latitude enhancements in the sodium exosphere has been variously ascribed to solar wind ion impacts, to radiation pressure, to inherent surface compositional and physical differences, and to cold trapping. Over the course of the mission, the science team hopes to determine the partitioning of sodium and other species between the thermal and non-thermal components to determine the processes of desorption from surface materials.
Rosemary Killen, of the University of Maryland, will discuss new discoveries derived from observations of sodium, calcium, and magnesium in the nightside and tail regions of the exosphere. "The dawn/dusk asymmetries are particularly intriguing," Killen says. "While sodium is a volatile element, calcium is not easily vaporized. Magnesium can be found in both volatile and refractory minerals. So a comparison of their relative distributions and time variations in the exosphere will help determine the important processes involved in loss and transport of surface materials."
The MESSENGER AGU presentations will be made in three separate sessions on Monday and Tuesday, December 15-16. The first of those sessions will be webcast. To view the session, go to the AGU Fall Meeting web page at http://www.agu.org/meetings/fm08/ and click on the appropriate session at the scheduled time (Pacific time). Individual speakers can be found in the Fall Meeting Scientific Program web pages.
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and after flybys of Earth, Venus, and Mercury will start a yearlong study of its target planet in March 2011. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
MESSENGER Completes Two-Part Maneuver; Poised for Third Mercury Encounter - December 8, 2008
MESSENGER completed the second part of a two-part deep-space maneuver today, providing the remaining 10% velocity change needed to place the probe on course to fly by Mercury for the third time in September 2009.
Unlike most maneuvers, this one was conducted in a so-called "open loop," explained MESSENGER Project Manager Peter Bedini. "In closed-loop maneuvers, the accelerometers are used to trim the burn, and thrusters are employed as needed to adjust the direction as perceived by the accelerometers," said Bedini, of the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Md. "To test the unlikely scenario that we will not have accelerometer data for the huge Mercury orbit insertion, we did this second part without using those data as feedback."
The first part of the maneuver, which occurred on December 4, increased the probe's speed relative to the Sun by 219 meters per second (489 miles per hour) to about 30.994 kilometers per second (69,333 miles per hour). Today's maneuver, which began at 3:30 p.m. EST, increased MESSENGER's speed by an additional 24.7 per second, for a total velocity change of 247 meters per second. Mission controllers at APL verified the start of the maneuver about 13 minutes, 18 seconds later, when the first signals indicating spacecraft thruster activity reached NASA's Deep Space Network tracking station in Canberra, Australia.
"We are now on target for the third Mercury flyby next September," Bedini said. "The fifth deep-space maneuver two months later will position MESSENGER for Mercury orbit insertion in March 2011," enabling it to become the first spacecraft to orbit the innermost planet.
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and after flybys of Earth, Venus, and Mercury will start a yearlong study of its target planet in March 2011. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
Deep-Space Maneuver Positions MESSENGER for Third Mercury Encounter - December 4, 2008
The Mercury-bound spacecraft MESSENGER completed the first part of a two-part deep-space maneuver today, providing the expected 90% of the velocity change needed to place the spacecraft on course to fly by Mercury for the third time in September 2009. A 4.5-minute firing of its bi-propellant engine increased the probe's speed relative to the Sun by 219 meters per second (489 miles per hour) to a speed of about 30.994 kilometers per second (69,333 miles per hour).
MESSENGER was 237.9 million kilometers (147.8 million miles) from Earth when today's maneuver began at 3:30 p.m. EST. Mission controllers at The Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Md., verified the start of the maneuver about 13 minutes, 14 seconds later, when the first signals indicating spacecraft thruster activity reached NASA's Deep Space Network tracking station outside Goldstone, Calif.
"It was a perfect maneuver," said APL's Eric Finnegan, MESSENGER Mission Systems Engineer. "Initial data analysis indicates an extremely accurate maneuver execution. After sifting through all the post-burn data I expect we will find ourselves right on target." The remaining 10% of this deep-space-maneuver's velocity change will be imparted to the spacecraft during the second part, which will occur on December 8, 2008. The total planned velocity change is 247 meters per second.
One final deep-space maneuver on November 29, 2009, will target the probe for Mercury orbit insertion in March 2011, making it the first spacecraft to orbit the planet closest to the Sun.
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and after flybys of Earth, Venus, and Mercury will start a yearlong study of its target planet in March 2011. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
Second Group of Mercury Craters Named - November 26, 2008
The International Astronomical Union (IAU) recently approved a proposal from the MESSENGER Science Team to name 15 craters on Mercury. All of the newly named craters were imaged during the mission's first flyby of the solar system's innermost planet in January 2008.
The IAU has been the arbiter of planetary and satellite nomenclature since its inception in 1919. In keeping with the established naming theme for craters on Mercury, all of the craters are named after famous deceased artists, musicians, or authors.
"We're pleased that the IAU has again acted promptly to approve this new set of names for prominent craters on Mercury," says MESSENGER Principal Investigator Sean Solomon of the Carnegie Institution of Washington. "These latest names honor a diverse suite of some of the most accomplished contributors to mankind's higher aspirations. They also make it much easier for planetary scientists to refer to major features on Mercury in talks and publications."
The newly named craters include:
• Amaral, after Tarsila do Amaral of Brazil, considered one of the leading Latin American modernist artists.
• Dalí, after Salvador Dalí, a Spanish painter and leader of the Surrealist Movement.
• Enwonwu, after sculptor and painter Benedict Chukwukadibia Enwonwu, the most renowned Nigerian artist of the 20th century.
• Glinka, after Mikhail Glinka, a Russian composer considered to be the "father" of genuinely Russian music.
• Hovnatanian, after Hakop Hovnatanian, an Armenian painter known for his portraits.
• Beckett, after Clarice Beckett, recognized as one of Australia's most important modernist artists.
• Moody, after Ronald Moody, a self-taught, Jamaica-born sculptor and painter who found success in mid-20th-century London and Paris.
• Munch, after Edvard Munch, a Norwegian Symbolist painter, printmaker, and draftsman, perhaps most well-known for his painting The Scream.
• Navoi, after Alisher Navoi, a 15th century Uzbek poet, considered by many to be the founder of early Turkic literature.
• Nawahi, after Joseph Nawahi, a self-taught artist, lawyer, educator, publisher, member of the Hawaiian legislature for many years, and principal adviser to Hawaii's Queen Lili'uokalani.
• Oskison, after John Milton Oskison, a Cherokee author who served as editor and editorial writer for the New York Evening Post.
• Poe, after Edgar Allan Poe, American poet, critic, editor, and author. Best known for his tales of mystery and the macabre.
• Qi Baishi, after Qi Baishi, a renowned Chinese painter known for his whimsical water colors.
• Raden Saleh, after Raden Saleh, a 19th century Javanese naturalist painter considered to be the first modern artist from what is now Indonesia.
• Sher-Gil, after Amrita Sher-Gil, an eminent Indian painter, today considered an important female painter of 20th-century India.
"It was quite enjoyable to consider candidate names from among the world's most accomplished people in the arts and humanities," says MESSENGER Participating Scientist Dave Blewett, of the Johns Hopkins University Applied Physics Laboratory, in Laurel, Md. "It's also gratifying to have the IAU approve names that have meaning to the team members. For example, the crater Poe (named for Edgar Allan Poe) was a popular choice, as he happens to be a local favorite because of his Baltimore ties.
"Having names for many of the prominent craters will help us to remember and discuss specific locations in this previously 'undiscovered country,'" adds Blewett.
An image of Mercury showing the locations of the newly named features is available online here.
The addition of these craters, along with the 12 features named in April, brings the total to 27 newly named surface features for Mercury in 2008. In September 2009 MESSENGER will complete a third and final flyby of Mercury before becoming the first spacecraft to orbit the planet, beginning in March 2011.
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and after flybys of Earth, Venus, and Mercury will start a yearlong study of its target planet in March 2011. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
MESSENGER Reveals More "Hidden" Territory on Mercury - October 29, 2008
Gliding over the battered surface of Mercury for the second time this year, NASA's MESSENGER spacecraft has revealed even more previously unseen real estate on the innermost planet, sending home hundreds of photos and measurements of its surface, atmosphere, and magnetic field.
The probe flew by Mercury shortly after 4:40 a.m. EDT on October 6, 2008, completing a critical gravity assist to keep it on course to orbit Mercury in 2011 and unveiling 30 percent of Mercury's surface never before seen by spacecraft.
"The region of Mercury's surface that we viewed at close range for the first time this month is bigger than the land area of South America," says Sean Solomon, MESSENGER principal investigator and the director of the Department of Terrestrial Magnetism at the Carnegie Institution of Washington. "When combined with data from our first flyby and from Mariner 10, our latest coverage means that we have now seen about 95% of the planet."
MESSENGER's science instruments worked feverishly through the flyby - cameras snapped more than 1,200 pictures of the surface, while topography beneath the spacecraft was profiled with the laser altimeter. "We have completed an initial reconnaissance of the solar system's innermost planet, enabling us to gain a global view of Mercury's geological history and internal magnetic field geometry for the first time," Solomon continues.
The comparison of magnetosphere observations from MESSENGER's first flyby in January with data from the probe's second pass has provided key new insight into the nature of the planet's internal magnetic field and revealed new features of Mercury's magnetosphere.
"The previous flybys by MESSENGER and Mariner 10 provided data only on Mercury's eastern hemisphere," explains Brian Anderson, of the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Md. "The most recent flyby gave us our first measurements on Mercury's western hemisphere, and with them we discovered that the planet's magnetic field is highly symmetric."
"This seemingly simple result is significant for the planet's internal field because it implies that the dipole is even more closely aligned with the planet's rotation axis than we could conclude before the second flyby," says Anderson, who is deputy project scientist. "Even though the rigorous analyses of these data are ongoing, we expect that this result will allow us to limit the theories of planetary magnetic field generation to those that predict a strongly rotationally aligned moment."
The Mercury Atmospheric and Surface Composition Spectrometer (MASCS) observed the extended tail, night side, and day side regions of Mercury's thin atmosphere - known as an exosphere - searching for emission from sodium, calcium, magnesium, and hydrogen atoms.
"The MASCS observations of magnesium are the first-ever detection of this species in Mercury's exosphere," explains MESSENGER participating scientist Ron Vervack of APL. Preliminary analysis of the sodium, calcium, and magnesium observations suggests that the spatial distributions of these three species are different and that the distribution of sodium during the second flyby is noticeably different from that observed during the first flyby.
"The spatial distributions of sodium, calcium, and magnesium are a reflection of the processes that release these species from Mercury's surface," Vervack adds. "Now that we were finally able to measure them simultaneously, we have an unprecedented window into the interaction of Mercury's surface and exosphere."
The probe's Mercury Laser Altimeter (MLA) measured the planet's topography, allowing scientists, for the first time, to correlate high-resolution topography measurements with high-resolution images.
"During the last flyby, the Mercury Laser Altimeter acquired a topographic profile in a hemisphere of the planet for which there were no spacecraft images," explains Maria Zuber, MESSENGER co-investigator and head of the Department of Earth, Atmospheric, and Planetary Sciences at the Massachusetts Institute of Technology. "During the second flyby, in contrast, altimetry was collected in regions where images from MESSENGER and Mariner 10 are available, and new images were obtained of the region sampled by the altimeter in January. These topographic measurements now improve considerably the ability to interpret surface geology."
Now that MESSENGER's cameras have imaged more than 80 percent of Mercury, it is clear that, unlike the Moon and Mars, the planet lacks hemispheric-scale geologic differences. "On the Moon, dark volcanic plains are concentrated on the near side and are nearly absent from the far side," says MESSENGER co-investigator Mark Robinson of Arizona State University. "On Mars, the southern hemisphere consists of older, cratered highlands, whereas the northern hemisphere consists of younger lowlands. Mercury's surface is more homogeneously ancient and heavily cratered, with large extents of younger volcanic plains lying within and between giant impact basins."
Color imaging also shows that Mercury's crust is compositionally heterogeneous. "Although definitive compositional interpretations cannot yet be made, the distribution of different components varies both across the surface and with depth - Mercury's crust is more analogous to a marbled cake than a layered cake," Robinson adds. "Once MESSENGER's suite of science instruments returns a host of data from the orbital phase of the mission, compositions will be determined for the newly discovered color units."
"The first two Mercury flybys have returned a rich dividend of new observations," says Solomon. "But some of the observations we are most eager to make - such as the chemical make-up of Mercury's surface and the nature of its enigmatic polar deposits - will not be possible until MESSENGER begins to orbit the innermost planet. Moreover, the very dynamic nature of Mercury's interaction with its interplanetary environment has taught us that continuous observations will be required before we can claim to understand our most sunward sister planet."
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and after flybys of Earth, Venus, and Mercury will start a yearlong study of its target planet in March 2011. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
MESSENGER Gains Speed - October 15, 2008
Shortly after 4 a.m. this morning, MESSENGER reached its greatest speed relative to the Sun. The spacecraft, nearly 70% closer to the Sun than Earth, was traveling nearly 140,880 miles per hour (62.979 kilometers per second) relative to the Sun. At this speed MESSENGER would traverse the distance from Earth to Earth's Moon in only 1.7 hours!
Even at this great speed MESSENGER is slightly slower than the fastest spacecraft: Helios 2. That spacecraft – launched into a solar orbit on January 15, 1976 – reached a top speed of 157,078 miles per hour (70.220 kilometers per second) relative to the Sun in April of 1976.
Because of MESSENGER's near-perfect Mercury flyby trajectory on October 6, the mission design and navigation team decided that a trajectory-correction maneuver (TCM) scheduled for October 28 will not be needed. The next maneuver for the mission, scheduled to be carried out in two parts on December 4 and December 8, will re-target the spacecraft for the third and final encounter with Mercury in just under a year on September 29, 2009.
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and after flybys of Earth, Venus, and Mercury will start a yearlong study of its target planet in March 2011. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
MESSENGER Sets Record for Accuracy of Planetary Flyby - October 8, 2008
By using solar sailing – rotating the spacecraft and tilting its solar panels to use the very small pressure from sunlight to alter the spacecraft's trajectory – MESSENGER navigators have achieved a new record for the smallest miss distance between the intended and actual closest approach distance during a flyby of a planet other than Earth.
On October 6, 2008, the probe flew 199.4 kilometers (123.9 miles) above the surface of the planet. "Our goal was to fly 200 kilometers from the planet's surface, and we missed that target by only 0.6 kilometers," explained MESSENGER Mission Design Lead Jim McAdams, of the Johns Hopkins University Applied Physics Laboratory in Laurel, Md.
That's pretty remarkable targeting, given that MESSENGER has travelled 668 million kilometers since its last deep space maneuver in March, McAdams says. "It's as if we shot an arrow from New York to a target in Los Angeles – nudged it three times mid-stream with a soft breath – and arrived within the width of the arrow's shaft at the target."
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and after flybys of Earth, Venus, and Mercury will start a yearlong study of its target planet in March 2011. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
MESSENGER Reveals Mercury as Never Seen Before - October 7, 2008
When Mariner 10 flew past Mercury three times in 1974 and 1975, the probe imaged less than half the planet. In January, during MESSENGER's first flyby, its cameras returned images of about 20 percent of the planet's surface missed by Mariner 10. Yesterday, at 4:40 am EDT, MESSENGER successfully completed its second flyby of Mercury, and its cameras captured more than 1,200 high-resolution and color images of the planet – unveiling another 30 percent of Mercury's surface that had never before been seen by spacecraft.
"The MESSENGER team is extremely pleased by the superb performance of the spacecraft and the payload," said MESSENGER Principal Investigator Sean Solomon of the Carnegie Institution of Washington. "We are now on the correct trajectory for eventual insertion into orbit around Mercury, and all of our instruments returned data as planned from the side of the planet opposite to the one we viewed during our first flyby. When these data have been digested and compared, we will have a global perspective of Mercury for the first time."
Today, at about 1:50 a.m. EDT, MESSENGER turned to Earth and began transmitting data gathered during its second Mercury encounter. This spectacular image – one of the first to be returned – was snapped by the Wide Angle Camera (WAC), part of the Mercury Dual Imaging System (MDIS) instrument, about 90 minutes after MESSENGER's closest approach to Mercury, when the spacecraft was at a distance of about 27,000 kilometers (about 17,000 miles).
The bright crater just south of the center of the image is Kuiper, identified on images from the Mariner 10 mission in the 1970s. For most of the terrain east of Kuiper, toward the edge of the planet, the departing images are the first spacecraft views of that portion of Mercury's surface. A striking characteristic of this newly imaged area is the large pattern of rays that extend from the northern region of Mercury to regions south of Kuiper.
This WAC image is one in a sequence of 55: a five-frame mosaic with each frame in the mosaic acquired in all 11 of the WAC filters. This portion of Mercury's surface was previously imaged under different lighting conditions by Mariner 10, but this new MESSENGER image mosaic is the highest-resolution color imaging ever acquired of any portion of Mercury's surface.
Additionally, some of the images in this mosaic overlap with flyby data acquired by the Mercury Atmospheric and Surface Composition Spectrometer and Mercury Laser Altimeter instruments, resulting in the first time that these three instruments have gathered data of the same area of Mercury. The combination of these three datasets will enable unprecedented studies of this region of Mercury's surface.
This image, acquired about 89 minutes before the craft's closest approach to Mercury, resembles the optical navigation images taken leading up to the flyby. The resolution of this image is somewhat better than that obtained by the final optical navigation image set, and the surface visible is newly imaged terrain that was not previously seen by either Mariner 10 or during MESSENGER's first flyby.
However, the added resolution is not the main scientific advancement that will be provided by this image. This WAC image is one of 11 viewed through different narrow-band color filters, the set of which will enable detailed color studies of this newly imaged area. In addition, the Narrow Angle Camera (NAC) acquired a high-resolution mosaic of most of this thin crescent view of Mercury at a resolution better than 0.5 kilometers/pixel (0.3 miles/pixel) that will enable the MESSENGER team to explore this newly imaged region of Mercury's surface in more detail.
About 58 minutes before MESSENGER's closest approach to Mercury, the NAC captured this close-up image of a portion of Mercury's surface imaged by spacecraft for the first time. It is one of 44 in a high-resolution NAC mosaic taken of the approaching crescent-shaped Mercury, as seen at lower resolution in the optical navigation images and the approach WAC color image set.
As the MESSENGER team is busy examining this newly obtained view, data from the flyby continue to stream down to Earth, including higher resolution close-up images of this previously unseen terrain. Collectively, these images and measurements made by other MESSENGER instruments will soon provide a broad range of information for understanding the formation and geologic history of the innermost planet.
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and after flybys of Earth, Venus, and Mercury will start a yearlong study of its target planet in March 2011. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
MESSENGER Flyby of Mercury - October 6, 2008
At a little after 4:40 a.m. EDT, MESSENGER skimmed 200 kilometers (124 miles) above the surface of Mercury in the second of three flybys of the planet. Initial indications from the radio signals indicate that the spacecraft continues to operate nominally. The spacecraft is now collecting images and other scientific measurements from the planet as it departs Mercury from the illuminated side, filling in the details of much of Mercury's surface not previously viewed by spacecraft.
Tomorrow at 1:14 a.m. EDT, the spacecraft will turn its high-gain antenna back toward Earth to start down-linking the data stored onboard. The first pictures from the flyby will be released around 10:00 a.m. on October 7, 2008. Additional information and features from this encounter will be available online at Flyby-Information.html. Be sure to check back frequently to see the latest released images and science results!
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and after flybys of Earth, Venus, and Mercury will start a yearlong study of its target planet in March 2011. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
MESSENGER Instruments Take Aim - October 5, 2008
MESSENGER's engineering and operations teams convened at the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Md., this afternoon to confirm the health and readiness of the spacecraft. "All spacecraft sub-systems and instruments reported nominal operations indicating that MESSENGER is ready for its second encounter with Mercury," said MESSENGER Systems Engineer Eric Finnegan of APL.
At 6:05 p.m. EDT the last bits of data from the spacecraft were received as it transitioned from high-gain downlink to beacon-only operations, and the spacecraft reoriented itself to begin science operations. Before turning away, however, the spacecraft returned a set of optical navigation images (available online here) of the terrain not yet seen up-close by any spacecraft to whet our appetite regarding the discoveries to come.
For the next 10 hours or so, the spacecraft will take repetitive scans through Mercury's comet-like anti-sunward tail, pausing now and then to take a color image and a high-resolution mosaic of Mercury with the Mercury Dual Imaging System instrument.
"The operations team is now preparing for the period of time about an hour prior to closest approach [at 4:40:21 a.m. EDT], when we will be transitioning our support from the Canberra ground station to the Madrid ground station that will capture the flyby," Finnegan said. "High-gain communications with the spacecraft will be re-established on Tuesday at 1:14 a.m. EDT at approximately 52 kilobits per second, and playback of the data stored in the solid-state recorder will start approximately 30 minutes later."
"MESSENGER is now on its own. The MESSENGER team is confident that our probe will carry out the full flyby command sequence, which was developed and thoroughly tested by the many dedicated engineers and scientists on the MESSENGER flight team," said MESSENGER Principal Investigator Sean Solomon of the Carnegie Institution of Washington. "We all look forward with excitement to the flyby data set that we will start to glimpse Tuesday morning. We'll be seeing at close range, for the first time, a region of Mercury larger in area than South America. Discoveries are just hours away."
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and after flybys of Earth, Venus, and Mercury will start a yearlong study of its target planet in March 2011. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
Closing in on Mercury - October 4, 2008
MESSENGER's mission design and navigation teams met today at the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Md., to discuss the spacecraft's current trajectory to determine if a last-minute trajectory-correction maneuver would be needed.
"Early this morning, the navigation team delivered the final ephemeris update for the spacecraft prior to the flyby," said APL's Eric Finnegan, the MESSENGER Mission Systems Engineer. "The data indicate that the last solar sailing attitude alternation implemented between Tuesday and Wednesday was a complete success. The current position estimate places the spacecraft within approximately 800 meters of the target! This is a phenomenal achievement for both the navigation and guidance and control teams."
"The operations team has confirmed that the core Mercury command load sequence was onboard the spacecraft, and all subsystems and instruments are operating nominally," Finnegan said. With less than two days to the flyby, MESSENGER is on target to encounter Mercury at an altitude of 200 kilometers (124 miles) on Monday, October 6, at approximately 4:41 a.m. EDT.
Over the next two days, the spacecraft will continue to gather optical navigation images approximately every eight hours, while the operations team monitors the spacecraft. You can view the latest one online here.
The entire operations and engineering teams will gather in the operations center at APL on Sunday to make one last assessment of the spacecraft before the core encounter sequence begins, rotating the probe away from the Earth to view once again the closest planet to the Sun, revealing terrain never before seen by spacecraft!
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and after flybys of Earth, Venus, and Mercury will start a yearlong study of its target planet in March 2011. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
MESSENGER Beams Back First Approach Images of Mercury - October 3, 2008
MESSENGER mission operators at the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Md., have received the first optical navigation images from the spacecraft. "We will be taking seven additional sets over the next three days as the spacecraft approaches the planet," said APL's Eric Finnegan, the Mission Systems Engineer.
Optical navigation is commonly used to tie the position of a spacecraft to the position of a target body to ensure a safe and well-positioned flyby, particularly when the position of the target body is uncertain or if the navigation process has not been validated in flight. "During the first encounter with Mercury, both of these issues were of concern to mission planners," Finnegan explained. "However, following the highly accurate flyby in January, the necessity of these images for critical trajectory planning was removed."
"For successful optical navigation, we need to see the target body in the same image sequence as the background star field," said MESSENGER's Navigation Team Chief Ken Williams of KinetX, Inc. "Stars are far away, so to us, it appears that their positions are fixed in space. By comparing where Mercury is in the field-of-view with the stars visible behind it, and by controlling where the camera is pointing, we can estimate the position of the spacecraft."
The Mercury Dual Imaging System (MDIS) instrument consists of two imagers, a wide-angle camera (WAC) with a 10.5º field of view, and a narrow-angle camera (NAC), with a 1.5º field of view. These imagers are always pointed at the same place, and the NAC footprint falls in the center of the WAC footprint. The WAC has a filter specially designed for imaging stars, most of which are so faint that long (up to 10-second) exposures are required.
The MESSENGER team employs both cameras for optical navigation, taking a star image with the WAC, and then quickly switching to the NAC for an image of the planet limb. Because the images are taken within seconds of each other, they can be used to see where the planet is compared with the star field.
The navigation images snapped during this flyby will also help the team plot MESSENGER's yearlong orbital survey of Mercury, which begins in March 2011. MESSENGER will fly very close to the surface of Mercury—within 200 kilometers (124 miles)—during the October 6 flyby, as it did in January. However, during this encounter, the navigation team will rely only on radiometric tracking data during closest approach.
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and after flybys of Earth, Venus, and Mercury will start a yearlong study of its target planet in March 2011. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
MESSENGER Returns to Mercury - October 1, 2008
On October 6, for the second time in less than a year, NASA's MESSENGER spacecraft will swoop just 200 kilometers (125 miles) above the cratered surface of Mercury, snapping hundreds of pictures and collecting a variety of other data from the planet as it gains a critical gravity assist that keeps the probe on track to become the first spacecraft ever to orbit the innermost planet beginning in March 2011.
"The results from MESSENGER's first flyby of Mercury in January resolved debates that are more than 30 years old," says Sean C. Solomon, MESSENGER principal investigator, from the Carnegie Institution of Washington. "Volcanic eruptions produced many of Mercury's plains, its magnetic field appears to be actively generated in a molten iron core, and the planet has contracted more than we thought." This second encounter, says Solomon, will uncover even more information about the planet.
Scoping New Territory
During MESSENGER's first flyby, its cameras returned images of about 20% of Mercury's surface not previously seen by spacecraft, revealing new and unexpected features. "During this second flyby, the cameras will take more than 1,200 high-resolution and color images of the planet, including 30% of Mercury's surface that has never been seen by spacecraft," says Louise M. Prockter, instrument scientist for MESSENGER's Mercury Dual Imaging System (MDIS) at the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Md. "MESSENGER's second flyby will show us a completely new area of Mercury's surface, opposite from the side of the planet we saw during the first flyby."
The probe's Mercury Laser Altimeter (MLA) will measure the planet's topography, allowing scientists, for the first time, to correlate high-resolution topography measurements with high-resolution images. "Unlike the topographic data obtained during our first flyby – which covered terrain we hadn't photographed from space – these MLA range measurements will cover areas MDIS imaged during that first pass," explains APL's Brian J. Anderson, MESSENGER's deputy project scientist. "Moreover, terrain sampled by MLA in the first flyby will in turn be imaged by MDIS on the second encounter."
The second flyby is also expected to yield more surprises about the unique physical processes governing Mercury's magnetosphere-exosphere system, as well as additional information about the charged particles located in and around Mercury's dynamic magnetosphere.
Surface Composition
A major goal of the orbital phase of MESSENGER's mission is to determine the composition of Mercury's surface, APL's Ralph L. McNutt, MESSENGER project scientist, points out. The instruments designed to make those compositional measurements – the Visible-Infrared Spectrograph (VIRS) on the Mercury Atmospheric and Surface Composition Spectrometer (MASCS), the X-Ray Spectrometer, and the Gamma-Ray and Neutron Spectrometer – will get another peek at Mercury during this flyby.
"The VIRS high-spatial-resolution spectral measurements of Mercury's surface will overlap with high-resolution color images taken by MDIS, providing complementary spectral information about portions of Mercury's surface in unprecedented detail," says McNutt. "The second flyby will also provide a first test of the spectral uniformity or variability between the two hemispheres viewed by MASCS in the two flybys."
MESSENGER is more than halfway through a 7.9-billion-kilometer (4.9-billion-mile) journey to Mercury orbit that includes more than 15 trips around the Sun. It has already flown past Earth once (August 2, 2005), Venus twice (October 24, 2006, and June 5, 2007), and Mercury once (January 14, 2008). The upcoming flyby and an additional pass of Mercury, in September 2009, will use the pull of the planet's gravity to guide MESSENGER progressively closer to Mercury, so that orbit insertion can be accomplished at the fourth Mercury encounter in March 2011.
"In addition to providing data that are already being used to start answering the guiding science questions of the mission, the observations made during the Mercury flybys are critical to the science planning effort," says MESSENGER Project Manager Peter D. Bedini, of APL. "The performance of the spacecraft and instruments during the flybys helps us prioritize and organize the observations to be made during the orbital phase."
The MESSENGER project is the seventh in NASA's Discovery Program of low-cost, scientifically focused space missions. Solomon leads the mission as principal investigator; APL manages the mission for NASA's Science Mission Directorate and designed, built, and operates the MESSENGER spacecraft. MESSENGER's science instruments were built by APL; NASA Goddard Space Flight Center, Greenbelt, Md.; University of Michigan, Ann Arbor; and the Laboratory for Atmospheric and Space Physics at the University of Colorado, Boulder; with the support of subcontractors across the United States and Europe. GenCorp Aerojet, Sacramento, Calif., and Composite Optics Inc., San Diego, Calif., respectively, provided MESSENGER's propulsion system and composite structure.
The MESSENGER Science Team, augmented by an impressive array of experts participating in NASA's MESSENGER Participating Scientist Program, includes 46 scientists from 25 institutions. A complete list can be found at ../About/Team.html#science-team. Additional information about MESSENGER is available on the Web at: http://messenger.jhuapl.edu.
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and after flybys of Earth, Venus, and Mercury will start a yearlong study of its target planet in March 2011. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
MLA Ready to Range to Mercury's Surface - September 29, 2008
One week from today, the MESSENGER spacecraft will fly by Mercury for the second time this year. As part of the final preparations for this encounter, the Mercury Laser Altimeter (MLA) has been powered on after having been off since shortly after the first flyby at the beginning of the year. The entire MESSENGER science payload is now powered and configured to collect data during next week's encounter.
"Right after the January flyby, the MLA completed passive observations of Mercury, without the laser firing, as a calibration," explained MLA Instrument Scientist Olivier Barnouin-Jha of the Johns Hopkins University Applied Physics Laboratory in Laurel, Md. "At that point it was switched off, and it has remained off since that time."
During MESSENGER's first Mercury encounter, the MLA provided the first direct measurements of the topography of Mercury from spacecraft. The results provide evidence for a complex geologic history and indicate that Mercury's craters are shallower than those on the Moon at a given crater diameter, as expected because of the higher surface gravity.
"Unlike the topographic data obtained during the first flyby, which were of terrain for which we have no space-based imaging, some of the area to which MLA will range during this second encounter was imaged by the Mercury Dual Imaging System (MDIS) during the first Mercury flyby," Barnouin-Jha said. Moreover, terrain sampled by MLA during the first flyby will in turn be imaged by MDIS during this visit.
"So this second flyby will allow the first inter-comparison between the topographic observations and high-resolution spacecraft images," he added.
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and after flybys of Earth, Venus, and Mercury will start a yearlong study of its target planet in March 2011. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
MESSENGER's Gamma-Ray Spectrometer Gears up for Mercury Flyby - September 22, 2008
Two weeks from today, the MESSENGER spacecraft will fly by Mercury for the second time. As part of the final preparations for this encounter, the Gamma-Ray Spectrometer (GRS) was placed in an "anneal mode" to prepare its detector for optimal performance during the flyby.
"The detector material itself is a high-purity crystal made of the element germanium," explains GRS Instrument Engineer John O. Goldsten. "In space, the crystal develops defects—atoms knocked out of place—when bombarded by high-energy cosmic radiation, and this degrades the instrument's performance. Heating the detector to high temperatures promotes realignment in the crystal, a process called annealing."
This annealing process increases the detector temperature to 84°C for a period of time before lowering it to an operating temperature of -183°C. The annealing will last for two weeks in preparation for Mercury flyby 2 to improve energy resolution and signal-to-background ratio. The GRS detector will be annealed once again prior to the third flyby of Mercury in September 2009, and once every Mercury year (88 Earth days) during the orbital phase of the mission.
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and after flybys of Earth, Venus, and Mercury will start a yearlong study of its target planet in March 2011. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
MESSENGER Finalizes Plans for Its Second Look at Mercury - September 12, 2008
It is now only slightly more than three weeks before the MESSENGER spacecraft flies by Mercury for the second time. At 4:40 a.m. ET on October 6, the craft will speed by the planet, passing within 125 miles (200 kilometers) and gaining a gravity assist that will tighten its orbit and keep it on its course to pass the planet one last time next year before becoming the first spacecraft ever to orbit Mercury, beginning in 2011.
A comprehensive set of observations of Mercury and its environment has been designed for this upcoming encounter – deploying all seven of the science payload instruments, in addition to the telecommunications system – to continue the investigations begun during the first encounter with Mercury last January.
Over the last six months, engineers have been building the software commands needed to implement these observations into one single sequence that will be loaded to the spacecraft to run automatically during the encounter. The development of this sequence included several levels of review and testing as it matured. Today, engineers successfully completed the final testing of the commands on the hardware simulator, and on September 29, engineers will send MESSENGER instructions on what observations to perform at each point along the flyby trajectory.
As MESSENGER flew by Mercury on January 14, its instruments imaged 20% of Mercury's surface not previously seen by spacecraft. The spacecraft made measurements of the planet's magnetic field, exosphere and sodium tail, surface color and composition, and gravitational field. On its second visit, MESSENGER will image an additional 30% of the surface never before seen by spacecraft.
"MESSENGER's first flyby of Mercury produced many surprises," offered MESSENGER Principal Investigator Sean Solomon. "The second flyby will bring us close to the opposite side of the planet from the one we visited in January, and the surface we will view at close range for the first time is larger in area than South America. The only safe prediction at this stage of exploring the innermost planet is that we will make new discoveries."
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and after flybys of Earth, Venus, and Mercury will start a yearlong study of its target planet in March 2011. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
MESSENGER Sails on Sun's Fire for Second Flyby of Mercury - September 5, 2008
On September 4, the MESSENGER team announced that it would not need to implement a scheduled maneuver to adjust the probe's trajectory. This is the fourth time this year that such a maneuver has been called off. The reason? A recently implemented navigational technique that makes use of solar-radiation pressure (SRP) to guide the probe has been extremely successful at maintaining MESSENGER on a trajectory that will carry it over the cratered surface of Mercury for a second time on October 6.
SRP is small and decreases by the square of the distance away from the Sun. But, unlike rockets, so-called solar sailing requires no fuel. And although SRP's thrust is small, it will continue as long as the Sun is shining and the "sail" is deployed, providing a continuous acceleration source for the probe.
MESSENGER's mission designers and its guidance and control team at the Applied Physics Laboratory in Laurel, Md., along with the navigation team, at KinetX, Inc., in Simi Valley, Calif., once viewed SRP as something of a challenge to overcome, particularly for the critical gravity-assist flybys – one of Earth, two of Venus, and three of Mercury – that the spacecraft would be executing to position it for Mercury orbit insertion in 2011.
"Because of the changing proximity to the Sun during MESSENGER's cruise phase, the SRP varies from one to 11 times the value experienced at Earth," explains APL's Daniel J. O'Shaughnessy, MESSENGER's Guidance and Control Lead Engineer. This variation in magnitude, as well as the attitude-dependent direction of the resulting disturbance force and torque, presents a significant challenge to mission designers and the guidance and control team, he says.
"The Mercury flybys are designed to take the probe within approximately 200 kilometers of the planet, so precision targeting is absolutely critical," O'Shaughnessy says. Fly too low and the probe could crash into the planet. Fly too far away and MESSENGER might have to use its reserve fuel to correct for the acceleration loss. Either way, getting off target could jeopardize the mission.
SRP was seen as an impediment to precise targeting, until the first Mercury flyby in January 2008. About 26 days before that historic event, MESSENGER fired its thrusters to fine-tune its trajectory and aim for the 200-kilometer-altitude flyby point. Prior to the maneuver, the probe was on a course to miss the flyby aim point by more than 2,000 kilometers.
After the maneuver, the probe was still about 9.5 kilometers off from its target. "We still had one more opportunity for another trajectory-correction maneuver four days before the flyby, but we were able to skip it by solar sailing the spacecraft closer to the intended aim point," explains APL's Jim McAdams, who designed MESSENGER's trajectory.
Three days earlier than originally planned, the team tilted MESSENGER's solar panels an extra 20 degrees away from the Sun. The resulting change in solar-array orientation moved the flyby altitude very close to the target aim point. Ultimately, MESSENGER missed its target altitude by only 1.4 kilometers. This targeting was "spectacular," McAdams says.
The MESSENGER team has planned a more extensive use of this technique for the second Mercury flyby. "We've developed a process to use the SRP force as a control for the trajectory," explains O'Shaughnessy. Using the knowledge developed from the first flyby, the team has developed a carefully planned sequence of probe-body attitude and solar-array orientations that, if all goes according to plan, should reduce the number of trajectory correction maneuvers needed in the future.
According to NASA, the only other visitor to Mercury used solar sailing. In 1974, when the Mariner 10 spacecraft ran low on attitude-control gas, its engineers angled the spacecraft's solar arrays into the Sun and used solar radiation pressure for attitude control, and it worked. But MESSENGER's use of the technique represents the first time that a spacecraft has successfully used solar sailing as a propulsion-free trajectory control method for the targeting of planetary flybys.
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and after flybys of Earth, Venus, and Mercury will start a yearlong study of its target planet in March 2011. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
Sharing the Wealth: MESSENGER Team Delivers Mercury Flyby 1 Data to Planetary Data System - August 4, 2008
Data from MESSENGER's first flyby of Mercury have been released to the public by the Planetary Data System (PDS), an organization that archives and distributes all of NASA's planetary mission data.
"This delivery, while not the first for the MESSENGER mission, represents a significant milestone," says MESSENGER Mission Archive Coordinator Alan Mick, of the Johns Hopkins University Applied Physics Laboratory. "We had delivered data from MESSENGER to the PDS before, but not Mercury data," he says. "This delivery was particularly significant — the first MESSENGER flyby of Mercury was mankind's return to this planet after an absence of over three decades. In this one flyby we imaged previously unseen areas of Mercury's surface, greatly improved the resolution in areas already covered, and made observations of a kind that had never been made before."
Calibrated data from three of the probe's science instruments — the Magnetometer (MAG), the Mercury Atmospheric and Surface Composition Spectrometer (MASCS), and the Mercury Dual Imaging System (MDIS) — are included in this release. "The science results from these instruments have already shed light on questions about Mercury that have lingered for more than three decades," says MESSENGER Project Scientist Ralph McNutt of APL.
For instance, analyses of data from MDIS have shown that volcanoes were involved in plains formation, and MAG results confirm that the planet's magnetic field is actively produced in the planet's core and is not a frozen relic. The MASCS instrument has provided new insights into the extent and complexity of the planet's tenuous exosphere. "The availability of these data via PDS will allow scientists around the world to study the data and begin making even more connections and discoveries," McNutt adds.
Since the mid-1990s, NASA has required all of its planetary missions to archive data in the PDS, an active archive that makes available well-documented, peer-reviewed data to the research community. "An essential element of the implementation of NASA missions is the dissemination of collected data to the science community at large," explains Marilyn Lindstrom, NASA Program Scientist for MESSENGER. "It's critical to maintain a planetary data archive that will withstand the test of time so that future generations of scientists can access, understand, and use pre-existing planetary data."
The PDS includes eight university/research center science teams, called discipline nodes, each of which specializes in specific areas of planetary data. The contributions from these nodes provide a data-rich source for scientists, researchers, and developers. Steven Joy of the University of California, Los Angeles, is MESSENGER's PDS liaison. His challenge was to coordinate the efforts of the nodes responsible for validating the various datasets before they could be released. "The PDS validation process needs to be comprehensive and unforgiving to ensure that only high-quality, well-documented data are released for use by the science community," Joy says. "The data archives do not need to be perfect, but they do need to be documented well enough that future users, unfamiliar with how the data were acquired, can understand the data and apply them to new problems."
The "formal" public release makes mission data available for several applications, including the MESSENGER Mercury flyby visualization tool, available online here. "The tool now includes actual, unprocessed images from the narrow-angle and wide-angle cameras, taken during the January flyby," says APL's James McAdams, who designed MESSENGER's trajectory. "Viewers will see the same images that told the team that the cameras were not only on target, but were revealing Mercury as it had never been seen before."
In addition, the "Science on a Sphere" exhibit at NASA's Goddard Space Flight Center's Visitor Center has now incorporated MESSENGER images into its collection of Solar System displays. This exhibit utilizes four video projectors to display three-dimensional data onto the surface of a six-foot, suspended sphere. "It's a unique opportunity to project high-resolution NASA data for educational purposes," notes MESSENGER Education and Public Outreach Project Manager Stephanie Stockman.
MESSENGER Principal Investigator Sean Solomon says it took high level of dedication for the team to pull this off. "Many members of the MESSENGER team devoted long hours and weekends to ensure that the project met the goal of releasing all of our Mercury data six months after the flyby. We are delighted to share these historic data with the scientific community and the public, and we hope that their availability will foster interest everywhere in the mysteries of the Sun's closest planetary neighbor."
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Happy Anniversary, MESSENGER!
It's been four years since MESSENGER was launched atop a Delta II rocket on August 3, 2004, and they have been busy years. Since it began its odyssey, the spacecraft has travelled 4.33 billion kilometers (2.69 billion miles) relative to the Sun. It has executed four planetary flybys (one of Earth on August 2, 2005; two of Venus, on October 24, 2006, and June 5, 2007; and one of Mercury, on January 14, 2008), three deep-space propulsive maneuvers, and 15 smaller trajectory-correction maneuvers. Up next are two more passes by Mercury (October 6, 2008, and September 29, 2009) and then on March 18, 2011, MESSENGER will become the first spacecraft to enter into orbit around the innermost planet.
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and after flybys of Earth, Venus, and Mercury will start a yearlong study of its target planet in March 2011. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
Scientists have argued about the origins of Mercury's smooth plains and the source of its magnetic field for over 30 years. Now, analyses of data from the January 2008 flyby of the planet by the MESSENGER spacecraft have shown that volcanoes were involved in plains formation and suggest that its magnetic field is actively produced in the planet's core and is not a frozen relic. Scientists additionally took their first look at the chemical composition the planet's surface material. The tiny craft probed the composition of Mercury's thin atmosphere, sampled charged particles (ions) near the planet, and demonstrated new links between both sets of observations and materials on Mercury's surface. The results are reported in a series of 11 papers published in a special section of the July 4 issue of Science(italic) magazine.
The controversy over the origin of Mercury's smooth plains began with the 1972 Apollo 16 Moon mission, which suggested that some lunar plains came from material that was ejected by large impacts and then formed smooth 'ponds.' When Mariner 10 imaged similar formations on Mercury in 1975, some scientists believed that the same processes were at work. Others thought that Mercury's plains material came from erupted lavas, but the absence of volcanic vents or other volcanic features in images from that mission prevented a consensus.
Six of the papers in Science report on analyses of the planet's surface through its reflectance and color variation, surface chemistry, high-resolution imaging at different wavelengths, and altitude measurements. The researchers found evidence of volcanic vents along the margins of the Caloris basin, one of the Solar System's largest and youngest impact basins. They also found that Caloris has a much more complicated geologic history than previously believed.
"By combining Mariner 10 and MESSENGER data, the science team was able to reconstruct a comprehensive geologic history of the entire basin interior," explained James Head of Brown University, the lead author of one of the Science reports. "The Caloris basin was formed from an impact by an asteroid or comet during the heavy bombardment period in the first billion years of Solar System history. As with the lunar maria, a period of volcanic activity produced lava flows that filled the basin interior. This volcanism produced the comparatively light, red material of the interior plains intermingled with impact crater deposits. Subsidence caused the surface of the Caloris floor to shorten, producing what we call wrinkle-ridges. The large troughs, or graben, then formed as a result of later uplift, and more recent impacts yielded newer craters."
The first altitude measurements from any spacecraft at Mercury also found that craters on that planet are about a factor of two shallower than those on the Moon and they, too, show a complex geologic history.
Mariner 10 discovered Mercury's magnetic field. Earth is the only other terrestrial planet with a global magnetic field. In both cases the field produces a protective bubble called a magnetosphere, which generally shields the planet surface from the charged particles of the solar wind. Earth's magnetic field is generated by the churning, hot, liquid-iron core via a mechanism called a magnetic dynamo. Researchers have been puzzled by Mercury's field since its iron core should have cooled long ago and stopped generating magnetism. Some researchers have thought that the field may have been a relic of the past, frozen in the outer crust.
"MESSENGER's measurements did indicate that, like the Earth, Mercury's magnetic field is mostly dipolar, which means it has a north and south magnetic poles," stated lead author Brian Anderson of the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Md. "The fact that it's dipolar, and that we did not find the 'signature' shorter-wavelength anomalies that would signify patches of magnetized crust, supports the view that we're seeing a modern dynamo. We are eager for the October flyby and the year in orbit to see if this is the case elsewhere on the planet and confirm that the field comes from the core."
The flyby made the first-ever observations of the ionized particles in Mercury's unique exosphere. The exosphere is an ultrathin atmosphere where the molecules are so far apart they are more likely to collide with the surface than with each other. The planet's highly elliptical orbit, its slow rotation, and particle interactions with the magnetosphere, interplanetary medium, and solar wind result in strong seasonal and day-night differences in the way particles behave.
"MESSENGER was able to observe Mercury's exosphere in three areas—the dayside, the day/night line, or terminator, and its 25,000 mile-long (40,000 km) sodium tail," explained lead author Bill McClintock of the University of Colorado. "Atoms of hydrogen, helium, sodium, potassium, and calcium have been seen in the exosphere, and many other elements almost certainly exist there. When species escape from the surface they are accelerated by solar-radiation pressure and form a long tail of atoms flowing away from the Sun. But their abundances differ depending on whether it's day or night, effects from the magnetic field and solar wind, and possibly the latitude. Mercury's exosphere is remarkably active."
"Since Mariner 10's discovery of Mercury's magnetosphere, there's been speculation about its dynamics, ion composition, and how the solar wind interacts with the surface and exosphere," commented lead author Thomas Zurbuchen of the University of Michigan. "The planet's surface is the most space-weathered of any terrestrial planet, and the interaction of solar wind and micrometeoroid flux with the surface can inject both neutral and charged particles into the exosphere and space. The ion composition was not measured by Mariner 10 and MESSENGER once again provided a significant scientific surprise. The magnetosphere is full of many ionic species, both atomic and molecular and in a variety of charge states. What is in some sense a 'Mercury plasma nebula' is far richer in complexity and makeup than the Io plasma torus in the Jupiter system. The abundances of silicon, sodium, and sulfur relative to oxygen in the solar wind are too low, and their charge states — ionization — are too high to account for the abundances we measured, so there is no doubt that this material came from the planet's surface. This observation means that this flyby got the first-ever look at surface composition."
Mercury's core makes up 60% of its mass, which is at least twice as large as any other planet. The flyby revealed that the magnetic field, originating in the outer core and powered by core cooling, drives very dynamic and complex interactions among the planet's interior, surface, exosphere, and magnetosphere.
Remarking on the importance of the core to surface geological structures, MESSENGER Principal Investigator Sean Solomon, at the Carnegie Institution of Washington, said: "The dominant tectonic landforms on Mercury, including areas imaged for the first time by MESSENGER, are features called lobate scarps, huge cliffs that mark the tops of crustal faults that formed during the contraction of the surrounding area. They tell us how important the cooling core has been to the evolution of the surface. After the end of the period of heavy bombardment, cooling of the planet's core not only fuels the magnetic dynamo, it also led to contraction of the entire planet. And the data from the flyby indicate that the total contraction is a least one third greater than we previously thought."
"When you look at the planet in the sky, it looks like a simple point of light," remarked MESSENGER Project Scientist Ralph McNutt, of APL. "But when you experience Mercury close-up through all of MESSENGER's 'senses' seeing it at different wavelengths, feeling its magnetic properties, and touching its surface features and energetic particles, you perceive a complex system and not just a ball of rock and metal. We are all surprised by how active that planet is and at the dynamic interrelationships among its core, surface, exosphere, and magnetosphere."
"It's remarkable that this rich lode of data came from two days of imaging, just 30 minutes of sampling the planet's magnetosphere and exosphere, and less than ten minutes carrying out altimetry and collecting other data near the time of its closest approach 125 miles (200 kilometers) to the surface," offered Solomon. "MESSENGER's first flyby was a huge success, both in keeping us on target for the rest of our journey and in advancing our progress toward answering the science questions that have motivated this mission."
Additional information is available online at Flyby-Information.html. For copies of the papers contact AAAS SciPak at 202-326-6440 or scipak@aaas.org.
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and after flybys of Earth, Venus, and Mercury will start a yearlong study of its target planet in March 2011. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
NASA to Reveal New Discoveries from Mercury - July 2, 2008
NASA will host a media teleconference Thursday, July 3, at 2 p.m. EDT, to discuss analysis of data from the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft's flyby of Mercury earlier this year.
The spacecraft is the first designed to orbit the planet closest to the Sun. It flew past Mercury on Jan. 14, 2008, and made the first up-close measurements since Mariner 10's final flyby in 1975.
Analyses of the data show volcanoes were involved in the formation of plains. The data also suggest the planet's magnetic field is actively produced in its core. In addition, the mission has provided the first look at the chemical composition of Mercury's surface. The results will be reported in a series of 11 papers published July 4 in a special section of Science magazine.
The teleconference participants are:
- Marilyn Lindstrom, program scientist, NASA Headquarters
- Sean Solomon, principal investigator, Carnegie Institution of Washington
- James W. Head III, professor of geological sciences, Brown University, Providence, R.I.
- William McClintock, senior research associate, Laboratory for Atmospheric and Space Physics, University of Colorado, Boulder
- Thomas H. Zurbuchen, associate professor, Department of Atmospheric, Oceanic and Space Sciences, University of Michigan, Ann Arbor
Reporters may access the embargoed science press package materials by registering with EurekAlert! at www.eurekalert.org and e-mailing scipak@aaas.org to expedite their registration. Once registered, they may log in directly at: http://www.eurekalert.org/jrnls/sci/.
To participate in the teleconference, reporters in the United States should call 1-888-455-3616 and use the passcode "messenger." International reporters should call 1-517-623-4705. Audio of the teleconference will be streamed live at:
http://www.nasa.gov/newsaudio.
When the briefing begins, related images will be available at:
http://messenger.jhuapl.edu/news_room/telecon4.html.
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and after flybys of Earth, Venus, and Mercury will start a yearlong study of its target planet in March 2011. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
Jim McAdams, the MESSENGER mission design lead engineer, was named the 2008 Engineer of the Year by the Baltimore Section, American Institute of Aeronautics and Astronautics (AIAA). Each spring, this chapter of AIAA honors those in the aerospace community who have made significant contributions during the previous year.
McAdams of the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Md., "optimized the trajectory and maneuver schedule, designing one of the most challenging planetary missions in history," said APL's Tom Strikwerda, who on May 28 presented the award: a plaque and a 24-inch-high trophy that McAdams will keep until passing it on to the next winner a year from now.
Because Mercury lies deep within the Sun's gravity well, travel to the planet requires an extremely large velocity change. A spacecraft travelling to Mercury speeds up as it falls toward the Sun; so MESSENGER's trajectory had to be designed to most effectively utilize the gravitational pull of Venus and Mercury to achieve most of the required velocity change.
To make the trip possible, the trajectory uses six gravity-assist flybys: one by Earth, two by Venus, and three by Mercury. These gravity-assists, along with five large course-correction maneuvers, reduce the energy (and thus fuel) requirements but greatly prolong the trip. These maneuvers will also slow the spacecraft's speed just enough relative to Mercury to enable its thruster to place the probe into orbit around Mercury.
Upon arrival at Mercury in March of 2011 the spacecraft will enter an elliptical orbit that passes as close as 200 kilometers to Mercury's far northern surface every 12 hours. Such an orbit will allow MESSENGER to measure solar wind and magnetic fields at a variety of distances from the planet yet still obtain close-up measurements and images of the surface.
"The implementation of this complex mission plan has been a significant challenge," says McAdams, who also worked on the Near Earth Asteroid Rendezvous mission. "It's a privilege to join two other MESSENGER team engineers as recipients of this award," he adds, referring to Robin Vaughan and Adrian Hill, two other engineers from the team who received the award in 2004 and 2006, respectively.
McAdams, who holds an M.S. in Aeronautical and Astronautical Engineering from Purdue University, also created and led the development of MESSENGER education and outreach products, as well as trajectory data distribution to the science community. Last summer, he played a critical role in the creation of the Mercury Flyby Visualization Tool, which provides simulated views of Mercury from MESSENGER's perspective, during approach, flyby, and departure, or in real time (as the observations actually occur).
Members of MESSENGER's Geology Discipline Group used the tool both before and after the probe's first flyby of Mercury in January to gain information about imaging sites on Mercury. The tool will be updated for upcoming Mercury encounters.
"Jim McAdams has been a critical member of the MESSENGER team," offers MESSENGER Principal Investigator Sean Solomon. "Jim is usually several steps ahead of the rest of us with respect to planning for mission-critical events, and we can always count on his results to high precision. The journey to orbiting Mercury is long and complex, but we have a terrific guide."
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and after flybys of Earth, Venus, and Mercury will start a yearlong study of its target planet in March 2011. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
Mercury Features Receive New Names - April 28, 2008
The International Astronomical Union (IAU) has approved new names for features on Mercury and agreed on a new theme for fossae on the planet. These newly christened features were discovered from images taken by the MESSENGER spacecraft during its first flyby of Mercury in January.
The IAU is the internationally recognized authority for assigning designations to surface features on celestial bodies. "We are very pleased with how quickly the IAU has responded to the need to name many of the prominent landforms on Mercury first seen in MESSENGER images," says MESSENGER Principal Investigator Sean Solomon of the Carnegie Institution of Washington. "The Science Team has just submitted our first scientific papers on the flyby observations, and this prompt action by the IAU has meant that we are able to refer to these features by their formal names."
Naming rules exist for most features on planets, moons, and asteroids. Mercury's cliffs are named after the ships of famous explorers. One set of cliffs discovered by MESSENGER (called by the Latin name for cliffs, rupes) is named Beagle Rupes, after the ship on which naturalist Charles Darwin sailed around the world.
Craters on Mercury are named after famous deceased artists, musicians, or authors. The approved crater names are:
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and after flybys of Earth, Venus, and Mercury will start a yearlong study of its target planet in March 2011. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
The MESSENGER spacecraft delivered a critical deep-space maneuver today – 64 million miles (103 million kilometers) from Earth – successfully firing its large bi-propellant engine to change the probe's trajectory and target it for its second flyby of Mercury on October 6, 2008. This was the first trajectory-correction maneuver (TCM) to test the continuous slow rotation of the spacecraft throughout the burn, essential for the March 18, 2011, Mercury orbit-insertion (MOI) maneuver.
"Every propulsive event in this complex mission is an important step toward our ultimate goal – placing the first spacecraft into orbit about the innermost planet," offers MESSENGER Principal Investigator Sean Solomon, of the Carnegie Institution of Washington. "Today's deep-space maneuver is a crucial milestone that points us cleanly toward our next close look at Mercury in October."
The 149-second maneuver began at 3:30 p.m. EDT. Mission controllers at The Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Md., verified the start of the maneuver about 5 minutes 42 seconds later, when the first signals indicating spacecraft thruster activity reached NASA's Deep Space Network tracking station outside Goldstone, California.
The continuous rotation of the spacecraft occurred during the 90-second firing of the large bi-propellant engine, the main part of the 149-second TCM, and was less than 4° – about 11% of the turn required for the mission-critical MOI. The total change in velocity of 72.2 meters per second (161.5 miles per hour) achieved during the maneuver will increase the spacecraft's speed relative to the Sun.
This was the third of five deep-space maneuvers that will help the spacecraft reach Mercury orbit. The first, on December 12, 2005, positioned the probe for its October 2006 flyby of Venus; the second, on October 17, 2007, targeted MESSENGER for its first flyby of Mercury this January.
DSM-4 on December 6, 2008, will position MESSENGER for Mercury flyby 3, scheduled for September 30, 2009. And the final deep-space maneuver on November 29, 2009, will target the probe for Mercury orbit insertion.
The next maneuver, TCM-24, is currently scheduled for April 24 and will be used to further fine-tune the trajectory for the second Mercury encounter. "There are also several instrument and subsystem calibrations this spring and summer, and even an instrument flight software load in July," says MESSENGER Mission Operations Manager Andy Calloway of APL. "The MESSENGER team will also continue to focus on the Mercury Flyby 2 sequence planning and testing, as well as orbital operations planning in parallel with the ongoing flight operations."
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and after flybys of Earth, Venus, and Mercury will start a yearlong study of its target planet in March 2011. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
MESSENGER Scientists to Discuss Findings From Mercury Flyby - March 7, 2008
During its January flyby of Mercury, the MESSENGER spacecraft observed swaths of the innermost planet never before seen up close. Members of the MESSENGER mission team will present findings from that historic encounter and discuss Mercury science during the 39th Lunar and Planetary Science Conference March 10-14 at the South Shore Harbour Resort and Conference Center in League City, Texas.
At 8:30 a.m. CDT, MESSENGER Principal Investigator Sean Solomon of the Carnegie Institution of Washington and science team member Mark Robinson of Arizona State University will chair a special session, "MESSENGER at Mercury I," in the Crystal Ballroom. A list of topics to be covered is available online at http://www.lpi.usra.edu/meetings/lpsc2008/pdf/sess101.pdf.
That afternoon, MESSENGER team members Faith Vilas (MMT Observatory) and Clark Chapman (Southwest Research Institute) will chair a follow-on special session, "MESSENGER at Mercury II," at 2:30 p.m. CDT in the Crystal Ballroom. A list of topics to be covered in this session is available online at http://www.lpi.usra.edu/meetings/lpsc2008/pdf/sess152.pdf.
Additional information and features from MESSENGER's first flyby of Mercury are online at Flyby-Information.html.
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and after flybys of Earth, Venus, and Mercury will start a yearlong study of its target planet in March 2011. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
Making a Mosaic - March 5, 2008
During MESSENGER's flyby of Mercury on January 14, 2008, the Mercury Dual Imaging System (MDIS) acquired images to create eight different mosaics. Shown here is an image context sheet with small thumbnail versions of the MDIS Narrow Angle Camera (NAC) images that were captured as the spacecraft approached the planet and used to create a high-resolution mosaic of Mercury.
The MDIS instrument is mounted on a pivot, which enables the camera to point in different directions and see different portions of the surface. Both small motions of the spacecraft and movement of the pivot were used to take the images that compose this mosaic sequence. This mosaic has images in 5 columns by 11 rows, but images of just black space or of the unlit, dark planet are not shown on this context sheet.
MDIS started this mosaic 55 minutes before MESSENGER's closest pass by Mercury. The first image of the mosaic was taken in the lower left corner, and images were subsequently acquired by moving across a row and then up to start the next row. An image where Mercury's surface fills the image is about 500 kilometers (310 miles) across.
Image names, which are abbreviated under each image in this context sheet, are derived from the mission elapsed time when the image was taken, which is approximately the time in seconds since launch. The mosaic was planned to have about 10% overlap between neighboring images, to ensure that a mosaic could be formed without any gaps. The resulting mosaic is ultimately created by using the time of each image and corresponding information about the spacecraft location and viewing geometry at that time to place all of the images onto a common map of Mercury.
Additional information and features from MESSENGER's first flyby of Mercury are online at Flyby-Information.html.
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and after flybys of Earth, Venus, and Mercury will start a yearlong study of its target planet in March 2011. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
Craters in Caloris - February 27, 2008
As MESSENGER sped by Mercury on January 14, 2008, the Narrow Angle Camera (NAC) of the Mercury Dual Imaging System (MDIS) captured this image, which includes the edge of the planet against the blackness of space. Much of the foreground shows a portion of Caloris basin, one of the largest impact basins in the solar system. The two large craters near the bottom of this image can be identified on the northwestern floor of the basin on the mosaicked image of Caloris released at MESSENGER's NASA press conference on January 30, 2008. The large crater in the bottom middle of this image has a diameter of about 70 kilometers (40 miles).
Caloris basin is an area of particular interest to the MESSENGER science team, since understanding its formation can lead to insights about the nature of large impacts in the early solar system and the results of these catastrophic events. In a false-color image of Mercury, also released on January 30, Caloris basin is visible in the northern hemisphere of the planet as a large, light-colored, roughly circular feature; the floor of the basin may have some differences in its composition compared with the darker surrounding surfaces.
The two large craters shown in today's released image are each surrounded by a "halo" of dark material, like the craters shown in our release of February 21. The smaller of the two craters has an unusual pattern of bright, highly reflective material on its floor. The fact that both of these craters, which show different material characteristics, are located within Caloris basin provides information about the variety and complexity of processes that have shaped Mercury's surface.
Additional information and features from MESSENGER's first flyby of Mercury are online at Flyby-Information.html.
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and after flybys of Earth, Venus, and Mercury will start a yearlong study of its target planet in March 2011. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
Craters with Dark Halos on Mercury - February 21, 2008
As MESSENGER flew by Mercury on January 14, 2008, the Narrow Angle Camera (NAC) of the Mercury Dual Imaging System (MDIS) captured this view. Two of the larger craters in this image appear to have darkened crater rims and partial "halos" of dark material immediately surrounding the craters. Both craters appear to have nearly complete rims and interior terraced walls, suggesting that they formed more recently than the other nearby shallower craters of similar size.
There are two possible explanations for their dark halos: (1) Darker subsurface material may have been excavated during the explosions from the asteroid or comet impacts that produced the craters. (2) Large cratering explosions may have melted a fraction of the rocky surface material involved in the explosions, splashing so-called "impact melts" across the surface; such melted rock is often darker (lower albedo) than the pre-impact target material. In either case, the association of the dark material with relatively recently formed craters suggests that the processes that gradually homogenize Mercury's surface materials have not yet had time to reduce the contrast of these dark halos.
The crater with associated dark material in the lower-left part of this image is about 100 kilometers (60 miles) in diameter, and the crater with patches of dark material in the upper right is about 70 kilometers (40 miles) across. These dark-halo craters, located near Mercury's south pole, are also visible in the previously released false-color image created from three Wide Angle Camera (WAC) frames.
Information from images taken in the 11 different color filters of the WAC will help MESSENGER scientists understand the nature of the dark material associated with the craters shown in this image and will determine whether they reveal the presence of subsurface material of a different composition, are examples of impact melt, or perhaps have some other explanation.
Additional information and features from MESSENGER's first flyby of Mercury are online at Flyby-Information.html.
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and after flybys of Earth, Venus, and Mercury will start a yearlong study of its target planet in March 2011. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
One Month Ago . . . - February 14, 2008
One month ago, on January 14, 2008, MESSENGER became the first spacecraft in over three decades to visit Mercury, snapping images of a large portion of the planet's surface previously unseen by spacecraft. As the spacecraft continues on its journey, the science team continues to study the 1,213 images returned from the mission's historic first flyby. The probe's trajectory will bring it to a second Mercury flyby on October 6, 2008.
MESSENGER's Narrow Angle Camera (NAC) of the Mercury Dual Imaging System (MDIS) captured this image during the flyby one month ago. The Sun is illuminating this region at a low angle, accentuating the modest ridges and other low topography on these nearly flat plains. Low ridges trend from the top-center of the image to the left edge (white arrows). The ghostly remains of craters are visible, filled to their rims by what may have been volcanic lavas (red arrows).
The faint remnant of an inner ring within the large crater in the bottom half of this picture can be seen (blue arrow); the area interior to this ring was also flooded, possibly by lava, nearly to the point of disappearance. Clusters of secondary craters on the floor of the large crater and elsewhere (yellow arrows) formed when clumps of material were ejected from large impacts beyond the view of this image, which is about 350 kilometers (220 miles) across.
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and after flybys of Earth, Venus, and Mercury will start a yearlong study of its target planet in March 2011. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
MESSENGER Team Begins Planning for Second Mercury Encounter - February 6, 2008
Little more than three weeks after MESSENGER's first historic flyby of Mercury, the team this week began mapping out its trajectory and observation plans for the probe's second pass of the planet this fall. On October 6, 2008, at 4:39 a.m. EST, the spacecraft will once again fly 200 kilometers (124 miles) above the surface of the planet.
This is the second of three scheduled passes of Mercury, each designed to provide a critical gravity assist needed to keep MESSENGER on track for its March 2011 orbit insertion around the planet. As with the first flyby on January 14, 2008, the spacecraft's full suite of instruments will be operating.
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and after flybys of Earth, Venus, and Mercury will start a yearlong study of its target planet in March 2011. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.
Surprises Stream back from Mercury's MESSENGER - January 30, 2008
After a journey of more than 2.2 billion miles and three and a half years, NASA's MESSENGER spacecraft made its first flyby of Mercury just after 2 PM Eastern Standard Time on January 14, 2008. All seven scientific instruments worked flawlessly, producing a stream of surprises that is amazing and delighting the science team. The 1,213 images conclusively show that the planet is a lot less like the Moon than many previously thought, with features unique to this innermost world. The puzzling magnetosphere appears to be very different from what Mariner 10 discovered and first sampled almost 34 years ago.
"This flyby allowed us to see a part of the planet never before viewed by spacecraft, and our little craft has returned a gold mine of exciting data," stated Sean Solomon, Principal Investigator and the Director of the Department of Terrestrial Magnetism at the Carnegie Institution of Washington. "From the perspectives of spacecraft performance and maneuver accuracy, this encounter was near-perfect, and we are delighted that all of the science data are now on the ground. The science team appreciates that this mission required a complex flight trajectory and a spacecraft that can withstand the intense thermal environment near the Sun. Without the hundreds of engineers and technicians at the Applied Physics Laboratory (APL) and all of the partner organizations who designed, assembled, tested, and now operate the spacecraft, we would not have been able to make any of the scientific observations now in hand."
"MESSENGER has shown that Mercury is even more different from the Moon than we'd thought," said Science Team Co-Investigator James Head, professor at Brown University and chair of the mission's Geology Discipline Group. The tiny spacecraft discovered a unique feature that the scientists dubbed, "The Spider." This type of formation has never been seen on Mercury before, and nothing like it has been observed on the Moon. It is in the middle of the Caloris basin and consists of over a hundred narrow, flat-floored troughs (called graben) radiating from a complex central region. "The Spider" has a crater near its center, but whether that crater is related to the original formation or came later is not clear at this time.
Unlike the Moon, Mercury also has huge cliffs or scarps, structures snaking up to hundreds of miles across the planet's face, tracing patterns of fault activity from early in Mercury's—and the solar system's—history. The high density and small size of Mercury combine to provide a surface gravity about 38% that of Earth and almost exactly the same as that of Mars, which is some 40% larger than Mercury in diameter (2.7 times Mercury's volume). Because gravity is stronger on Mercury than on the Moon, impact craters appear very different from lunar craters; material ejected during impact on Mercury falls closer to the rim and many more secondary crater chains are present.
"We have seen new craters along the terminator on the side of the planet viewed by Mariner 10 where the illumination of the MESSENGER images revealed very subtle features. Technological advances that have been incorporated in MESSENGER are effectively revealing an entirely new planet from what we saw over 30 years ago," said Science Team Co-Investigator Robert Strom, professor emeritus at the University of Arizona and the only member of both the MESSENGER and Mariner 10 science teams.
Now that MESSENGER has shown scientists the full extent of the Caloris basin, its diameter has been revised upward from the Mariner 10 estimate of 800 miles to perhaps as large as 960 miles (about 1550 kilometers) from rim crest to rim crest. The plains inside the Caloris basin are distinctive and have a higher reflectance —-albedo—-than the exterior plains, the opposite characteristics from many lunar impact basins such as the Imbrium basin on the Moon, yet another new mystery for Mercury. This finding could be the result of several processes—-when the basin was formed by a large impact, deeper material may have been excavated that contributed to impact melt now preserved on the basin floor; alternatively, the basin interior may have been volcanically resurfaced by magma produced deep in Mercury's crust or mantle subsequent to the impact. The science team is eagerly exploring the possibilities.
"MESSENGER found that Mercury's intrinsic magnetic field is almost identical to what it was 30 years ago. After correcting for the contribution from the solar wind interaction, the mean dipole has the same intensity to within a few percent and has the same slight tilt. The search is now on for structure in the internal field to identify its source," said Brian Anderson, the Magnetometer (MAG) instrument scientist.
Magnetic fields like Earth's, and their resultant magnetospheres, are generated by electrical dynamos operating deep in the planet in a liquid metallic outer core. Of the four terrestrial planets, only Mercury and Earth—the smallest and largest—exhibit such a structure. The magnetic field stands off the solar wind from the Sun, in effect producing a protective bubble around Earth that, with the Earth's thick atmosphere, shields the surface of our planet from sporadic energetic particles from the Sun and the more constant and more energetic cosmic rays from farther out in the galaxy. Earth's magnetic field does not stay the same; it moves around and the poles periodically flip, over geologic ages, changing the exposure of the surface to these dangerous particles. Similar variations are expected for Mercury's field, but the nature of its field-producing dynamo and the times between the corresponding changes are unknown at this time.
The next two flybys and the yearlong orbital phase will shed more light on this surprise. Mercury's global magnetic field has been a particular puzzle to scientists. The planet's small size should have resulted in the cooling and solidification of a liquid core long ago, quenching any dynamo activity. How this small world continues to maintain a magnetic field has been a major conundrum to planetary scientists. Solving this puzzle will help understand the history of Earth's magnetic field and why there are no modern global magnetic fields at Venus and Mars.
Ultraviolet emissions detected by the Ultraviolet and Visible Spectrometer (UVVS) segment of the Mercury Atmospheric and Surface Composition Spectrometer (MASCS) clearly showed sodium, calcium, and hydrogen in Mercury's exosphere (an atmosphere that is so thin that atoms comprising it rarely, if ever, collide).There is an abundance of sodium in an exospheric "tail" extending in an approximately antisunward direction from the planet by over 25,000 miles (40,000 km). During the MESSENGER flyby, there was a strong north-south asymmetry in the density of both sodium and hydrogen in Mercury's tail, perhaps a signature of the dynamic state at the time of the interaction of the solar wind with Mercury's magnetosphere and surface.
The suite of instruments that measured, for the first time, the elemental and mineralogical composition of Mercury's surface include the X-Ray Spectrometer (XRS), the Gamma-Ray and Neutron Spectrometer (GRNS), and the Visible and Infrared Spectrograph VIRS) portion of MASCS. They all operated as planned. Despite the fast flyby, the GRNS acquired observations vital to the interpretation of measurements that will be made during the orbital phase. XRS relies on the Sun's X-ray output to produce fluorescence in Mercury's surface elements, so the increase in solar activity when MESSENGER nears and enters the orbital phase of the mission will improve the resolution of the XRS for elemental remote sensing. Detailed analysis of spectra from VIRS, along with the color images, has just begun to provide insight into the mineralogical makeup of surface materials along the spacecraft's ground track.
The Mercury Laser Altimeter also worked flawlessly, providing a topographic profile of craters and other geological features along the spacecraft's flight path at all altitudes less than about 930 miles (1500 km) on the night side of the planet. Precise tracking and signal acquisition following the occultation of the spacecraft by the planet, in the minutes just prior to closest approach, enabled the acquisition of new information on the long-wavelength variations in the planet's gravitational field. In turn, these results will shed light on the size of Mercury's dense metallic core.
"But," says Project Scientist Ralph McNutt of APL, "we should keep this treasure trove of data in perspective. With two flybys yet to come and an intensive orbital mission to follow, 'You ain't seen nothing yet.'"
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and after flybys of Earth, Venus, and Mercury will start a yearlong study of its target planet in March 2011. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery -class mission for NASA.
MESSENGER's Departing Shots - January 29, 2008
After MESSENGER completed its successful flyby of Mercury, the Narrow Angle Camera (NAC), part of the Mercury Dual Imaging System (MDIS), took images of the receding planet. Beginning on January 14, 2008, about 100 minutes after MESSENGER's closest pass by the surface of Mercury, until January 15, 2008, about 19 hours later, the NAC acquired one image every four minutes. In all, 288 images were snapped during this sequence; shown here are just 12 of those departing shots.
The top left image was taken when MESSENGER was about 34,000 kilometers (21,000 miles) from Mercury, and the bottom right image was snapped from a distance of about 400,000 kilometers (250,000 miles).
This large set of departing NAC images has been assembled into a movie, which will be shown tomorrow during a NASA press conference at 1 p.m. EST. The briefing will take place in the NASA Headquarters' James E. Webb Auditorium, 300 E Street, S.W., Washington, and will be carried live on NASA Television.
On hand to talk about major findings from MESSENGER's historic flyby will be:
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and after flybys of Earth, Venus, and Mercury will start a yearlong study of its target planet in March 2011. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery -class mission for NASA.
A Closer Look at the Previously Unseen Side of Mercury - January 28, 2008
Two weeks ago, on January 14, 2008, MESSENGER became the first spacecraft to see the side of Mercury shown in this image. The first image transmitted back to Earth following the flyby of Mercury, and then released to the web within hours, shows the historic first look at the previously unseen side. This image, taken by the Wide Angle Camera (WAC) of the Mercury Dual Imaging System (MDIS), shows a closer view of much of that territory.
Just above and to the left of center of this image is a small crater with a pronounced set of bright rays extending across Mercury's surface away from the crater. Bright rays are commonly made in a crater-forming explosion when an asteroid strikes the surface of an airless body like the Moon or Mercury. But rays fade with time as tiny meteoroids and particles from the solar wind strike the surface and darken the rays. The prominence of these rays implies that the small crater at the center of the ray pattern formed comparatively recently.
This image is one in a planned set of 99. Nine different views of Mercury were snapped in this set to create a mosaic pattern with images in three rows and three columns. The WAC is equipped with 11 narrow-band color filters, and each of the nine different views was acquired through all 11 filters. This image was taken in filter 7, which is sensitive to light near the red end of the visible spectrum (750 nm), and shows features as small as about 6 kilometers (4 miles) in size. The MESSENGER team is studying this previously unseen side of Mercury in detail to map and identify new geologic features and to construct the planet's geological history.
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and after flybys of Earth, Venus, and Mercury will start a yearlong study of its target planet in March 2011. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery -class mission for NASA.
Mercury's Long Cliffs - January 27, 2008
As the MESSENGER team continues to study the high-resolution images taken during the Mercury flyby encounter on January 14, 2008, scarps (cliffs) that extend for long distances are discovered. This frame, taken by the Narrow Angle Camera (NAC) of the Mercury Dual Imaging System (MDIS), shows a region of Mercury's surface previously unseen by spacecraft and a large scarp crossing vertically through the scene, on the far right of the image. This scarp is the northern continuation of the one seen in the NAC image released on January 16. The width of this image is about 200 kilometers (about 125 miles), showing that these scarps can be hundreds of kilometers long on Mercury.
The presence of many long and high scarps, as discovered from pictures from the Mariner 10 mission in 1974 and 1975, suggests a history for Mercury that is unlike that of any of the other planets in the solar system. These giant scarps are believed to have formed when Mercury's interior cooled and the entire planet shrank slightly as a result. However, Mariner 10 was able to view less than half the planet, so the global extent of these scarps has been unknown. MESSENGER images, like this one, are providing the first high-resolution looks at many areas on Mercury's surface, and science team members are busy mapping these newly discovered scarps to see whether they are common everywhere on the planet.
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and after flybys of Earth, Venus, and Mercury will start a yearlong study of its target planet in March 2011. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery -class mission for NASA.
MESSENGER Looks to the North - January 26, 2008
As MESSENGER sped by Mercury on January 14, 2008, the Narrow Angle Camera (NAC) of the Mercury Dual Imaging System (MDIS) captured this shot looking toward Mercury's north pole. The surface shown in this image is from the side of Mercury not previously seen by spacecraft. The top right of this image shows the limb of the planet, which transitions into the terminator (the line between the sunlit, day side and the dark, night side) on the top left of the image. Near the terminator, the Sun illuminates surface features at a low angle, casting long shadows and causing height differences of the surface to appear more prominent in this region.
It is interesting to compare MESSENGER's view to the north with the image looking toward the south pole, released on January 21. Comparing these two images, it can be seen that the terrain near the south pole is more heavily cratered while some of the region near the north pole shows less cratered, smooth plains material, consistent with the general observations of the poles made by Mariner 10. MESSENGER acquired over 1200 images of Mercury's surface during its flyby, and the MESSENGER team is busy examining all of those images in detail, to understand the geologic history of the planet as a whole, from pole to pole.
This image was acquired about 94 minutes after MESSENGER's closest approach to Mercury, when the spacecraft was at a distance of about 32,000 kilometers (20,000 miles).
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and after flybys of Earth, Venus, and Mercury will start a yearlong study of its target planet in March 2011. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery -class mission for NASA.
MESSENGER's Different Views - January 25, 2008
During MESSENGER's flyby of Mercury on January 14, 2008, part of the planned sequence of observations included taking images of the same portion of Mercury's surface from five different viewing angles. The first view from this sequence was taken just after MESSENGER made its closest approach to Mercury, from a low viewing angle; an image of the first view was released on January 19. The image released here, acquired with the Wide Angle Camera (WAC) on the Mercury Dual Imaging System (MDIS), was snapped 13 minutes after MESSENGER's closest approach with Mercury. The lower two-thirds of this image shows much of the same terrain seen in the first view, but from a much higher viewing angle, as the spacecraft began to pass nearly overhead. At the time of this image, MESSENGER was at a distance of about 3000 kilometers (about 2000 miles) from Mercury.
A comparison of the images taken at different viewing angles provides important information about the properties of the materials that make up Mercury's surface. In addition, each view was taken through all 11 of the WAC's narrow-band color filters. The image shown here is from filter 7, which is sensitive to light near the red end of the visible spectrum (750 nm). The MESSENGER team is working to compare these images taken from different perspectives and in different colors to understand surface properties on Mercury. In addition, knowledge of the variation of image properties with viewing angle in this region will permit a more confident comparison of images of other portions of the surface taken at different illumination and viewing angles.
This image is about 1,000 kilometers (about 600 miles) across.
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and after flybys of Earth, Venus, and Mercury will start a yearlong study of its target planet in March 2011. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery -class mission for NASA.
Counting Mercury's Craters - January 24, 2008
On January 14, 2008, MESSENGER flew by Mercury and snapped images of a large portion of the surface that had not been previously seen by spacecraft. Ever since the first images were received back on Earth one day later, January 15, MESSENGER team members have been closely examining and studying this "new" terrain with great interest and excitement.
One of many investigations underway includes identifying and measuring the impact craters on these previously unseen regions. The density of craters on the surface of a planet can be used to indicate the relative age of different places on the surface; the more craters the surface has accumulated, the older the surface. By counting craters on different areas of Mercury's surface, a relative geologic history of the planet can be constructed, indicating which surfaces formed first and which formed later.
However, this process is also time consuming; Mercury has a lot of craters! This image shows just a portion (276 kilometers, or 172 miles, wide) of one frame taken with the Narrow Angle Camera (NAC) of the Mercury Dual Imaging System (MDIS). In this image alone, 763 craters have been identified and measured (shown in green) along with 189 hills (shown in yellow). Altogether, 491 frames were taken by the NAC to create high-resolution mosaics of Mercury's surface.
Of course, simply counting the craters is not enough. Each crater has to be measured and classified to fully interpret the differences in crater density. Many small craters form as "secondaries," as clumps of material ejected from a "primary" crater re-impact the surface in the regions surrounding the primary. In order to learn about the history of asteroid and comet impacts on Mercury, scientists have to distinguish between the primary and secondary craters. Once many more craters are measured, MESSENGER researchers will have new insights into the geological history of Mercury.
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and after flybys of Earth, Venus, and Mercury will start a yearlong study of its target planet in March 2011. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery -class mission for NASA.
MESSENGER Dances by Matisse - January 23, 2008
As MESSENGER approached Mercury on January 14, 2008, the Narrow Angle Camera (NAC) of the Mercury Dual Imaging System (MDIS) snapped this image of the crater Matisse. Named for the French artist Henri Matisse, the Matisse crater was imaged during the Mariner 10 mission and is about 210 kilometers (130 miles) in diameter. Matisse crater is in the southern hemisphere and can be seen near the terminator of the planet (the line between the sunlit, day side and the dark, night side) in both the color and single-filter, black-and-white images released previously that show an overview of the entire incoming side of Mercury.
On Mercury, craters are named for people, now deceased, who have made contributions to the humanities, such as artists, musicians, painters, and authors. The International Astronomical Union (IAU) oversees the official process of naming new craters and other new features discovered on bodies throughout the solar system. Scientists studying and mapping unnamed features can suggest names for consideration by the IAU. The 1,213 images taken by MESSENGER during its first flyby encounter with Mercury cover a large region of Mercury's surface previously unseen by spacecraft, revealing many new craters and other features that will need to be named.
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and after flybys of Earth, Venus, and Mercury will start a yearlong study of its target planet in March 2011. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery -class mission for NASA.
Mercury in Color! - January 22, 2008
One week ago, the MESSENGER spacecraft transmitted to Earth the first high-resolution image of Mercury by a spacecraft in over 30 years since the three Mercury flybys of Mariner 10 in 1974 and 1975. MESSENGER's Wide Angle Camera (WAC), part of the Mercury Dual Imaging System (MDIS), is equipped with 11 narrow-band color filters, in contrast to the two visible-light filters and one ultraviolet filter that were on Mariner 10's vidicon camera. By combining images taken through different filters in the visible and infrared, the MESSENGER data allow Mercury to be seen in a variety of high-resolution color views not previously possible. MESSENGER's eyes can see far beyond the color range of the human eye, and the colors seen in the accompanying image are somewhat different from what a human would see.
This color image was generated by combining three separate images taken through WAC filters sensitive to light in different wavelengths; filters that transmit light with wavelengths of 1000, 700, and 430 nanometers (infrared, far red, and violet, respectively) were placed in the red, green, and blue channels, respectively, to create this image. The human eye is sensitive across only the wavelength range 400 to 700 nanometers. Creating a false-color image in this way accentuates color differences on Mercury's surface that cannot be seen in the single-filter, black-and-white images released last week.
This visible-infrared image shows an incoming view of Mercury, about 80 minutes before MESSENGER's closest pass of the planet on January 14, 2008, from a distance of about 27,000 kilometers (17,000 miles).
Image sequences acquired through the 11 different MDIS filters are being used to distinguish subtle color variations indicative of different rock types. By analyzing color differences across all 11 filters, the MESSENGER team is investigating the variety of mineral and rock types present on Mercury's surface. Such information will be key to addressing fundamental questions about how Mercury formed and evolved.
Mercury has a diameter of about 4,880 kilometers (3,030 miles), and the smallest feature visible in this color image is about 10 kilometers (6 miles) in size.
First MESSENGER Spectrum of Mercury
During its flyby of Mercury, the MESSENGER spacecraft acquired the first high-resolution spectra of the planet's surface in ultraviolet, visible, and near-infrared light. The image on the left shows a portion of the ground-track along which the Mercury Atmospheric and Surface Composition Spectrometer (MASCS) instrument accumulated over 650 observations of the surface. The depicted area is about 300 kilometers (190 miles) across. The white track covers about 60 of the MASCS "footprints" or spectral snapshots. The red area highlights about 20 footprints averaged to make the example spectrum on the right, showing the relative amount of sunlight reflected from the surface at wavelengths from the ultraviolet to the visible (rainbow) to the infrared. The observations were taken on January 14, 2008, beginning as the spectrometer's field of view crossed into the day-lit side of the planet at a distance of about 1,900 kilometers (about 1,200 miles), and continuing until the field of view left the planet at a distance of about 8,500 kilometers (about 5,300 miles) from Mercury. Mercury is about 4880 kilometers (about 3030 miles) in diameter, and the footprints shown here are about 1 by 5 kilometers (0.6 by 3.4 miles).
The Mercury spectrum shows the degree to which different wavelengths of sunlight are absorbed or reflected by its surface materials. Dips in the spectrum indicate where sunlight shining on the surface is partially absorbed. The absorption bands' sizes and colors are diagnostic of the minerals in surface rocks. While Mercury has been observed telescopically from Earth for centuries, and Mariner 10 took images in one ultraviolet and two color filters when it flew by in 1974 and 1975, MESSENGER is the first mission to observe the surface with enough spatial and spectral resolution to determine Mercury's surface composition.
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and after flybys of Earth, Venus, and Mercury will start a yearlong study of its target planet in March 2011. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery -class mission for NASA.
Looking Toward the South Pole of Mercury - January 21, 2008
One week ago, on January 14, 2008, MESSENGER passed 200 kilometers (124 miles) above the surface of Mercury and snapped the first pictures of a side of Mercury not previously seen by a spacecraft. This image shows that previously unseen side, with a view looking toward Mercury's south pole. The southern limb of the planet can be seen in the bottom right of the image. The bottom left of the image shows the transition from the sunlit, day side of Mercury to the dark, night side of the planet, a transition line known as the terminator. In the region near the terminator, the sun shines on the surface at a low angle, causing the rims of craters and other elevated surface features to cast long shadows, accentuating height differences in the image.
This image is just one in a planned sequence of 42 images acquired by the Narrow Angle Camera of the Mercury Dual Imaging System (MDIS). From these 42 images, the MESSENGER team is creating a high-resolution mosaic image of this previously unseen portion of Mercury. During the flyby, MDIS took more than 1,200 images, which are being combined to create multiple mosaics with different resolutions and of different portions of the planet. The creation of high-resolution mosaic images will enable a global view of Mercury's surface and will be used to understand the geologic processes that made Mercury the planet we see today.
This image was acquired about 98 minutes after MESSENGER's closest approach to Mercury, when the spacecraft was at a distance of about 33,000 kilometers (21,000 miles).
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and after flybys of Earth, Venus, and Mercury will start a yearlong study of its target planet in March 2011. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery -class mission for NASA.
Latest MESSENGER Images Show Fascinating Views of Mercury's Surface - January 20, 2008
MESSENGER Views an Intriguing Crater
MESSENGER's Narrow Angle Camera (NAC) on the Mercury Dual Imaging System (MDIS) acquired this view of Mercury's surface illuminated obliquely from the right by the Sun. The unnamed crater (52 kilometers, or 31 miles, in diameter) in the center of the image displays a telephone-shaped collapse feature on its floor. Such a collapse feature, not seen on the floors of other craters in this image, could reflect past volcanic activity at and just below the surface of this particular crater.
MESSENGER team members are examining closely the more than 1,200 images returned from this flyby for other surface features that can provide clues to the geological history of the innermost planet.
The crater is located in the southern hemisphere of Mercury, on the side that was not viewed by Mariner 10 during any of its three flybys in 1974 and 1975. This scene was imaged while MESSENGER was departing from Mercury from a distance of about 19,300 kilometers (12,000 miles), about one hour after the spacecraft's closest encounter with Mercury. The image is of a region approximately 236 kilometers (147 miles) across, and craters as small as 1.6 kilometers (1 mile) can be seen.
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and after flybys of Earth, Venus, and Mercury will start a yearlong study of its target planet in March 2011. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery -class mission for NASA.
New Images Reveal Views after Closest Approach, First Mercury Laser Altimeter Results - January 19, 2008
MESSENGER's First Image after Closest Approach
Just nine minutes after MESSENGER passed 200 kilometers (124 miles) above the surface of Mercury – its closest distance to the planet during the January 14, 2008, flyby – the probe's Wide Angle Camera (WAC) on the Mercury Dual Imaging System (MDIS) snapped this image. The WAC is equipped with 11 different narrow-band filters, and this image was taken in filter 7, which is sensitive to light near the red end of the visible spectrum (750 nm). This view, also imaged through the remaining 10 WAC filters, is from the first set of images taken following MESSENGER's closest approach with Mercury.
The image shows Mercury's surface as seen from a low viewing angle, looking over the surface and off the limb of the planet on the right side of the image. The cratered terrain in the image is on the side of Mercury unseen by spacecraft prior to this MESSENGER flyby. This scene was imaged at multiple viewing angles as MESSENGER sped away from Mercury, and these multiple views of the same surface features from different perspectives and in different colors will be used to help understand the properties of Mercury's surface.
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and after flybys of Earth, Venus, and Mercury will start a yearlong study of its target planet in March 2011. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery -class mission for NASA.
MESSENGER's Mercury Flyby Science Data Now Safely on Earth - January 18, 2008
A day after its successful flyby of Mercury, the MESSENGER spacecraft turned toward Earth on Tuesday and began downloading the 500 megabytes of data that had been stored on the solid-state recorder during the encounter. All of those data, including 1,213 images from the Mercury Dual Imaging System (MDIS) cameras, have now been received by the Science Operations Center at the Johns Hopkins University Applied Physics Laboratory in Laurel, Md. Preliminary analysis of these data by the MESSENGER Science Team has confirmed that all seven MESSENGER instruments are healthy and operated as planned during the flyby.
As MESSENGER flew by the planet, it missed its targeted aim point by only 8.25 kilometers (5.12 miles), affording the critical gravity assist needed to continue on a course to become – in 2011 – the first spacecraft ever to orbit Mercury. During this first encounter, the payload successfully conducted a carefully orchestrated sequence of observations designed to take full advantage of the geometry of the flyby trajectory and to optimize the science return from each instrument.
In addition to images of the previously unseen portion of the planet's surface, measurements were made that will contribute to the characterization of all aspects of Mercury and its environment, from its metallic core to the far reaches of its magnetosphere. "We have one excited Science Team," says MESSENGER Project Manager, Peter D. Bedini, of APL, "and their enthusiasm is contagious."
The analysis of these data is just beginning, but there are already indications that new discoveries are at hand.
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and after flybys of Earth, Venus, and Mercury will start a yearlong study of its target planet in March 2011. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery -class mission for NASA.
New Images Shed Light on Mercury's Geological History, Surface Textures - January 17, 2008
MESSENGER Reveals Mercury's Geological History
Shortly following MESSENGER's closest approach to Mercury on January 14, 2008, the spacecraft's Narrow Angle Camera (NAC) on the Mercury Dual Imaging System (MDIS) instrument acquired this image as part of a mosaic that covers much of the sunlit portion of the hemisphere not viewed by Mariner 10. Images such as this one can be read in terms of a sequence of geological events and provide insight into the relative timing of processes that have acted on Mercury's surface in the past.
The double-ringed crater pictured in the upper right of this image appears to be filled with smooth plains material, perhaps volcanic in nature. This crater was subsequently disrupted by the formation of a prominent scarp (cliff), the surface expression of a major crustal fault system, that runs alongside part of its southern rim and may have led to the uplift seen across a portion of the crater's floor. A smaller crater in the upper left of the image has also been cut by the scarp, showing that the fault beneath the scarp was active after both of these craters had formed.
The MESSENGER team is working to combine inferences about the timing of events gained from this image with similar information from the hundreds of other images acquired by MESSENGER to extend and refine the geological history of Mercury previously defined on the basis only of Mariner 10 images.
This MESSENGER image was taken from a distance of about 18,000 kilometers (11,000 miles) from the surface of Mercury, at 20:03 UTC, about 58 minutes after the closest approach point of the flyby. The region shown is about 500 kilometers (300 miles) across, and craters as small as 1 kilometer (0.6 mile) can be seen in this image.
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and after flybys of Earth, Venus, and Mercury will start a yearlong study of its target planet in March 2011. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery -class mission for NASA.
Two New Images from MESSENGER's First Flyby of Mercury - January 16, 2008
Detailed Close-up of Mercury's Previously Unseen Surface
Just 21 minutes after MESSENGER's closest approach to Mercury on January 14, 2008, the Narrow Angle Camera (NAC) took this picture showing a variety of intriguing surface features, including craters as small as about 300 meters (about 300 yards) across.
This is one of a set of 68 NAC images showing landscapes near Mercury's equator on the side of the planet never before imaged by spacecraft. From such highly detailed close-ups, planetary geologists can study the processes that have shaped Mercury's surface over the past 4 billion years.
One of the highest and longest scarps (cliffs) yet seen on Mercury curves from the top center down across the right side of this image. (The Sun is shining low from the left, so the scarp casts a wide shadow.) Great forces in Mercury's crust have thrust the terrain occupying the left two-thirds of the picture up and over the terrain to the right. An impact crater has subsequently destroyed a small part of the scarp near the top of the image.
This image was taken from a distance of only 5,800 kilometers (3,600 miles) from surface of the planet and shows a region about 170 kilometers (about 100 miles) across.
Mercury's Cratered Surface
During its flyby of Mercury, the MESSENGER spacecraft acquired high-resolution images of the planet's surface. This image, taken by the Narrow Angle Camera (NAC) on the Mercury Dual Imaging System (MDIS), was obtained on January 14, 2008, about 37 minutes after MESSENGER's closest approach to the planet. The image reveals the surface of Mercury at a resolution of about 360 meters/pixel (about 1,180 feet/pixel), and the width of the image is about 370 kilometers (about 230 miles).
This image is the 98th in a set of 99 images that were taken in a pattern of 9 rows and 11 columns to enable the creation of a large, high-resolution mosaic of the northeast quarter of the region not seen by Mariner 10. During the encounter with Mercury, the MDIS acquired image sets for seven large mosaics with the NAC.
This image shows a previously unseen crater with distinctive bright rays of ejected material extending radially outward from the crater's center. A chain of craters nearby is also visible. Studying impact craters provides insight into the history and composition of Mercury as well as dynamical processes that occurred throughout our Solar System. The MESSENGER Science Team has begun analyzing these high-resolution images to unravel these fundamental questions.
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and after flybys of Earth, Venus, and Mercury will start a yearlong study of its target planet in March 2011. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery -class mission for NASA.
MESSENGER Reveals Mercury in New Detail - January 16, 2008
As MESSENGER approached Mercury on January 14, 2008, the spacecraft's Narrow-Angle Camera on the Mercury Dual Imaging System (MDIS) instrument captured this view of the planet's rugged, cratered landscape illuminated obliquely by the Sun. The large, shadow-filled, double ringed crater to the upper right was glimpsed by Mariner 10 more than three decades ago and named Vivaldi, after the Italian composer. Its outer ring has a diameter of about 200 kilometers (about 125 miles). MESSENGER's modern camera has revealed detail that was not well seen by Mariner 10, including the broad ancient depression overlapped by the lower-left part of the Vivaldi crater.
The MESSENGER science team is in the process of evaluating later images snapped from even closer range showing features on the side of Mercury never seen by Mariner 10. It is already clear that MESSENGER's superior camera will tell us much that could not be resolved even on the side of Mercury viewed by Mariner's vidicon camera in the mid-1970s.
This MESSENGER image was taken from a distance of about18,000 kilometers (11,000 miles), about 56 minutes before the spacecraft's closest encounter with Mercury. It shows a region roughly 500 kilometers (300 miles) across, and craters as small as 1 kilometer (0.6 mile) can be seen in this image.
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and after flybys of Earth, Venus, and Mercury will start a yearlong study of its target planet in March 2011. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery -class mission for NASA.
MESSENGER's First Look at Mercury's Previously Unseen Side - January 15, 2008
When Mariner 10 flew past Mercury three times in 1974 and 1975, the same hemisphere was in sunlight during each encounter. As a consequence, Mariner 10 was able to image less than half the planet. Planetary scientists have wondered for more than 30 years about what spacecraft images might reveal about the hemisphere of Mercury that Mariner 10 never viewed.
On January 14, 2008, the MESSENGER spacecraft observed about half of the hemisphere missed by Mariner 10. This image was snapped by the Wide Angle Camera, part of the Mercury Dual Imaging System (MDIS) instrument, about 80 minutes after MESSENGER's closest approach to Mercury (2:04 p.m. EST), when the spacecraft was at a distance of about 27,000 kilometers (about 17,000 miles). The image shows features as small as 10 kilometers (6 miles) in size. This image was taken through a filter sensitive to light near the red end of the visible spectrum (750 nm), one of a sequence of images taken through each of MDIS's 11 filters.
Like the previously mapped portion of Mercury, this hemisphere appears heavily cratered. It also reveals some unique and distinctive features. On the upper right is the giant Caloris basin, including its western portions never before seen by spacecraft. Formed by the impact of a large asteroid or comet, Caloris is one of the largest, and perhaps one of the youngest, basins in the Solar System. The new image shows the complete basin interior and reveals that it is brighter than the surrounding regions and may therefore have a different composition. Darker smooth plains completely surround Caloris, and many unusual dark-rimmed craters are observed inside the basin. Several other multi-ringed basins are seen in this image for the first time. Prominent fault scarps (large ridges) lace the newly viewed region.
Other images obtained during the flyby will reveal surface features in color and in much more detail. Collectively, these images and measurements made by other MESSENGER instruments will soon provide a detailed global view of the surface of Mercury, yielding key information for understanding the formation and geologic history of the innermost planet.
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and after flybys of Earth, Venus, and Mercury will start a yearlong study of its target planet in March 2011. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery -class mission for NASA.
Mercury Flyby Observations Are on the Way! - January 15, 2008
At 16:30 UTC (11:30 a.m. EST) today, MESSENGER flight controllers at the Johns Hopkins University Applied Physics Laboratory in Laurel, Md., received the first telemetry from the spacecraft following the probe's closest approach to Mercury yesterday. All spacecraft subsystems and instruments are operating normally, and telemetry data indicate that the command sequence during the flyby executed as expected.
The data from the probe - which include 1,213 images - are scheduled to start coming down to the Deep Space Network in Canberra, Australia in a few hours. As soon as the downlink transmission is complete, the MESSENGER Science Team will complete the processing of the first images.
"We are delighted with the successful outcome of the flyby," said MESSENGER Principal Investigator Sean Solomon of the Carnegie Institution of Washington. "The MESSENGER team is now eagerly awaiting the return of all of the scientific observations made over the past two days. We hope to share, within the next 24 hours, a first look at the side of Mercury never before seen at close range."
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and after flybys of Earth, Venus, and Mercury will start a yearlong study of its target planet in March 2011. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery -class mission for NASA.
MESSENGER Flyby of Mercury - January 14, 2008
At 2:04 p.m. EST MESSENGER skimmed 200 kilometers (124 miles) above the surface of Mercury in the first of three flybys of the planet. Initial indications from the radio signals indicate the spacecraft is still operating nominally. The first science data return from the flyby was received today, just minutes before the closest approach point with the planet, as planned.
"The engineers and operators at the Deep Space Network (DSN) in Goldstone, Calif., in conjunction with engineers at the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Md., pulled off a tremendous feat, acquiring and locking onto the downlink signal from the spacecraft within seconds, providing the necessary Doppler measurements for the Radio Science team" said MESSENGER Mission Systems Engineer Eric Finnegan, of APL." The spacecraft is continuing to collect imagery and other scientific measurements from the planet as we now depart Mercury from the illuminated side, documenting for the first time the previously unseen surface of the planet."
Tomorrow at noon EST, the spacecraft will turn back towards the Earth to start down-linking the on-board stored data. Measurements of this Doppler signal from the spacecraft will allow improve knowledge of Mercury's gravity field.
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and after flybys of Earth, Venus, and Mercury will start a yearlong study of its target planet in March 2011. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery -class mission for NASA.
Today MESSENGER Flies by Mercury! - January 14, 2008
Today, at 19:04:39 UTC (2:04:39 pm EST), MESSENGER will fly 200 kilometers (124 miles) above Mercury's surface. As the spacecraft continues to speed toward the planet, the Narrow Angle Camera, part of the Mercury Dual Imaging System (MDIS) instrument, acquired this crescent view of Mercury. The image was taken on January 13, when the spacecraft was about 760,000 kilometers (470,000 miles) from Mercury. Mercury is about 4,880 kilometers (about 3,030 miles) in diameter, and the smallest feature visible in this image is about 20 kilometers (12 miles) across.
During the historic encounter today, extensive scientific data will be gathered. The MDIS cameras will acquire more than 1,200 images of Mercury, including images of portions of the surface never before viewed by a spacecraft. The Mercury Atmospheric and Surface Composition Spectrometer will observe Mercury's surface as well as its tenuous atmosphere. The Magnetometer will accurately measure Mercury's magnetic field, and the Energetic Particle and Plasma Spectrometer will characterize Mercury's space environment and interactions with the solar wind. The Mercury Laser Altimeter will sense surface topography along a narrow profile. The Gamma-Ray and Neutron Spectrometer and X-Ray Spectrometer will make the first measurements of Mercury's surface elemental composition.
MESSENGER will begin to transmit the new data to Earth once all of the scientific measurements are completed, about 22 hours after the spacecraft's closest approach to Mercury. These flyby data will shed light on fundamental scientific questions related to the formation and evolution of the planet Mercury. As scientists analyze the data, the MESSENGER spacecraft will continue on its planned journey, which includes two more encounters of Mercury in October 2008 and September 2009, before entering an orbit around Mercury in March 2011.
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and after flybys of Earth, Venus, and Mercury will start a yearlong study of its target planet in March 2011. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery -class mission for NASA.
MESSENGER Instruments Take Aim - January 13, 2008
MESSENGER's engineering and operations teams convened at the Johns Hopkins University Applied Physics Laboratory in Laurel, Md., early this morning to confirm the health and readiness of the spacecraft.
At 7:56 a.m. EST the last bits of data from the spacecraft were received as it transitioned from high-gain downlink to beacon-only operations, turning the Mercury Dual Imaging System (MDIS) instrument toward the planet to start the approach color movie sequence. For the next 24 hours or so, the spacecraft will take three color frames of the planet every 20 minutes. When MESSENGER approaches within 39,000 kilometers (24,233.5 miles) of Mercury, the Mercury Atmospheric and Surface Composition Spectrometer instrument will start interleaving sweeps of the planet's anti-sunward tail at ultraviolet and visible wavelengths.
"The spacecraft is now on autopilot, executing the more than 5,000-line on-board command sequence and dutifully capturing the data from this historic flyby," said APL's Eric Finnegan, the MESSENGER Systems Engineer. "The operations team and the radio science team are now preparing for the post-occultation period, where operators at the Deep Space Network in Goldstone, Calif., will test their skill at capturing the spacecraft's radio signal, just minutes before closet approach with the planet, providing critical measurements for determining the mass distribution within Mercury."
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and after flybys of Earth, Venus, and Mercury will start a yearlong study of its target planet in March 2011. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery -class mission for NASA.
The Calm before Close Approach - January 12, 2008
MESSENGER's mission design and navigation teams at the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Md., met yesterday to discuss the spacecraft's current trajectory to determine if a last-minute trajectory-correction maneuver would be needed.
The accumulated radiometric tracking data gathered since the last maneuver indicated that MESSENGER's current position is within 13 kilometers of the target aim point for the Mercury flyby, and direct optical measurements of the planet over the last four days are confirming this result. "The consistency of the radiometric and optical measurements of the trajectory ensure that the spacecraft is on target for the encounter," explained MESSENGER Mission Systems Engineer Eric Finnegan of APL. The bottom line? Trajectory-correction maneuver (TCM) 21, scheduled for execution on January 13, is not needed.
"Using these current predictions," Finnegan said, "the spacecraft will fly by the planet within 4 kilometers (2.5 miles) of the target altitude - Bull's Eye!" With just two days to the flyby, MESSENGER is on target to encounter Mercury at an altitude of 203 kilometers (126 miles) at approximately 19:04:39 UTC (2:04 p.m. EST).
"Operations has confirmed that the core Mercury command load sequence was on-board the spacecraft Thursday night, and all subsystems and instruments are operating nominally," Finnegan said. "On Friday night, the Gamma-Ray Spectrometer turned on its cooler in preparation for the flyby, and the Mercury Laser Altimeter was powered up this morning. The spacecraft is now fully configured for the encounter. All systems are 'GO' for flyby!"
The MESSENGER team will assemble in the operations center early Sunday morning to take one last look at the spacecraft before it starts to execute the core command sequence and turn its instrumentation toward Mercury for the first time in the mission. On to history …
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and after flybys of Earth, Venus, and Mercury will start a yearlong study of its target planet in March 2011. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery -class mission for NASA.
Three Days to Mercury! - January 11, 2008
The countdown to the first flyby of Mercury by the MESSENGER spacecraft has begun. Sunday morning, MESSENGER will start recording the evidence of this historic event. At 8 a.m. EST on January 13 – 30 hours before the closest approach to Mercury – the spacecraft will turn its main antennas away from Earth and automatically begin executing the 5,000 on-board stored commands.
"The entire instrumentation suite will be operating during this flyby, taking more than 1,200 images and gathering other scientific observations, filling the on-board data recorder with more than 700 megabytes of history-making measurements, within a period of 55 hours," said MESSENGER Systems Engineer Eric Finnegan of the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Md. "Fifty minutes prior to closet approach, signals from the spacecraft will go quiet as MESSENGER passes behind Mercury, out of Earth's view. Forty-eight minutes later, engineers and scientists on the ground will attempt to witness the gravitational pull of the planet first-hand by re-acquiring the transmitted signal from the spacecraft within minutes of the closet approach point."
On Tuesday, January 15, at noon EST, 22 hours after the flyby, MESSENGER will take one last look at Mercury before turning back to Earth to start returning the treasures stored on-board. "Complicating this sequence of events is the demanding requirement to conduct all observations by the spacecraft behind the safety of MESSENGER's sunshade," Finnegan said. "Conducting this encounter at 30 million miles from the Sun, almost two-thirds closer than the Earth, would have been impossible in the era of Mariner 10. But thanks to advances in material sciences, MESSENGER's electronics and sensitive instruments can run at room temperature behind the sunshade, while the front surface temperature rises to more than 600° F."
Notwithstanding the operational and scientific importance of this flyby, MESSENGER is only slightly more than halfway along its six-and-one-half year, 4.9 billion-mile journey between its launch in August 2004 and orbit insertion around Mercury in March 2011. "Over the next 12-month period, the MESSENGER team will engage in the most grueling year of operations since launch, executing two planetary encounters, two deep space maneuvers, and possibly six additional maneuvers – using the smaller thrusters of the on-board propulsion system – to keep the spacecraft on course," added Finnegan.
The primary goal of this flyby is to obtain a gravity assist from the planet, which will reduce the arrival velocity of the spacecraft for orbit insertion in March 2011. "Slowing the spacecraft by 5,000 miles per hour, MESSENGER's orbital period around the Sun will be decreased by 11 days, thus setting up a planetary car race with Mercury," Finnegan said. "Using its internal engine and future gravity assists, the spacecraft, after being lapped by Mercury many times in this race around the Sun, will ultimately match the 88-day orbital period of the innermost planet."
To facilitate this change in velocity, the spacecraft will speed over the uncharted surface of Mercury at a relative velocity of more than 16,000 miles per hour and pass within 124 miles of the surface, the closest any man-made object has been to this planet. During this close approach, the spacecraft will experience a period of 14 minutes without solar power, where operations will rely only on the spacecraft's internal batteries.
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and after flybys of Earth, Venus, and Mercury will start a yearlong study of its target planet in March 2011. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery -class mission for NASA.
MESSENGER Set for Historic Mercury Flyby - January 10, 2008
NASA will return to Mercury for the first time in almost 33 years on January 14, 2008, when the MESSENGER spacecraft makes its first flyby of the Sun's closest neighbor, capturing images of large portions of the planet never before seen. The probe will make its closest approach to Mercury at 2:04 p.m. EST that day, skimming 200 kilometers (124 miles) above its surface. This encounter will provide a critical gravity assist needed to keep the spacecraft on track for its 2011 orbit insertion around Mercury.
"The MESSENGER Science Team is extremely excited about this flyby," says Dr. Sean C. Solomon, MESSENGER principal investigator, from the Carnegie Institution of Washington. " We are about to enjoy our first close-up view of Mercury in more than three decades, and a successful gravity assist will ensure that MESSENGER remains on the trajectory needed to place it into orbit around the innermost planet for the first time."
During the flyby, the probe's instruments will make the first up-close measurements of the planet since Mariner 10's third and final flyby of Mercury on March 16, 1975, and will gather data essential to planning the MESSENGER mission's orbital phase. MESSENGER's seven scientific instruments will begin to address the mission goals of:
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and after flybys of Earth, Venus, and Mercury will start a yearlong study of its target planet in March 2011. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery -class mission for NASA.
MESSENGER Team Receives First Optical Navigation Images - January 9, 2008
MESSENGER mission operators at the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Md., have received the first eight optical navigation images from the spacecraft. "We're going to be taking these images every day, up until just before the flyby, to make sure that we are on target for our aim point above the surface of Mercury," said Louise Prockter of APL, the instrument scientist for the Mercury Dual Imaging System (MDIS).
Optical navigation is commonly used to tie the position of a spacecraft to the position of a target body to ensure a safe and well-positioned flyby. Because MESSENGER will fly very close to the surface of Mercury during the January 14 flyby, optical navigation is used to provide an independent method for finding and correcting subtle errors in the trajectory. "This information will enable the navigation team to verify that the spacecraft is in the correct position for the flyby, or whether a last-minute maneuver will be needed to avoid either coming too close to the planet or missing it by so much that a large amount of fuel would be needed to return the probe to its optimum trajectory," Prockter noted.
To determine the position of the spacecraft, it is necessary to see the target body – in this case, Mercury – in the same field of view as the background star field, using MDIS. "The stars are far away, so their positions may be assumed to be fixed in space," Prockter said. "The position of Mercury along its orbit is also well known from hundreds of years of ground-based telescopic observations. Thus, by comparing where Mercury is in the field of view to the stars visible behind it, and by controlling where the camera is pointing, we can estimate the position of the spacecraft."
The MDIS instrument consists of two imagers, a Wide Angle Camera (WAC) with a 10.5º field of view, and a Narrow Angle Camera (NAC), with a 1.5º field of view. These imagers are always pointed at the same place, and the NAC footprint falls in the center of the WAC footprint. The WAC has a filter specially designed for imaging stars, most of which are so faint that long (up to 10-second) exposures are required.
"Unfortunately, such long exposures tend to saturate bright objects, such as Mercury, making it difficult to image both the planet and the stars in the same WAC image," Prockter said. "The NAC is not sensitive enough to see stars, but it has a resolution ~7 times better than the WAC and is excellent for imaging the planet limb."
To carry out optical navigation with MESSENGER, the team uses a combination of the two imagers, taking a star image with the WAC, then quickly switching to the NAC and taking an image of the planet limb. Because the images are taken within seconds of each other, they can be used to see where the planet is compared with the star field.
"The navigation team has obtained practice optical navigation images on previous flybys of Earth and Venus, but the Mercury encounter is the first time we have used this method 'for real' to determine the position of the MESSENGER spacecraft," Prockter said.
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and after flybys of Earth, Venus, and Mercury will start a yearlong study of its target planet in March 2011. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery -class mission for NASA.
Six Days from Mercury and Counting! - January 8, 2008
The MESSENGER spacecraft continues to approach Mercury and will be less than 3 million kilometers (1.9 million miles) away from the planet at the end of today. In just six days – on January 14, 2008, at 2:04 p.m. EST – the probe will pass a mere 200 kilometers (124 miles) above Mercury's surface. Extensive scientific observations are planned during this historic flyby, the first spacecraft flyby of Mercury in more than 30 years.
Mission operators at the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Md., recently sent MESSENGER a series of commands to acquire nine sets of optical navigation images at the planet Mercury. "This technique was tested and validated after MESSENGER's second flyby of Venus in June 2007," explained MESSENGER Mission Operations Manager Andy Calloway. "The Mercury Dual Imaging System camera will be used to further refine knowledge of the spacecraft trajectory by taking a sequence of Mercury limb images that include known bright stars in the camera's field of view as the spacecraft approaches Mercury."
MESSENGER Principal Investigator Sean Solomon of the Carnegie Institution of Washington discussed the importance of the historic flyby during a Planetary Radio show aired on January 7. "I was a very junior assistant professor at MIT back when Mariner 10 flew by Mercury three times in 1974 and 1975," Dr. Solomon told host Mat Kaplan. "It made some important discoveries that raised some questions that have been with us for three decades. So to be returning to Mercury – initially with this flyby but ultimately to go into orbit – with a modern suite of instruments to answer those three-decade-old questions has all of us at the edge of our seats." The entire interview is available online at http://www.planetary.org/radio/show/00000270/.
To celebrate MESSENGER's first flyby of the planet Mercury, APL and the Planetary Society will host a public reception on the evening of the encounter. The event will be held in APL's Parsons Auditorium from 7:00 to 8:00 p.m. The featured speaker is Robert G. Strom, a professor emeritus of lunar and planetary studies at The University of Arizona. Strom was involved in the Mariner 10 mission, the first and only previous mission to Mercury, and he is now a member of the MESSENGER Science Team. He'll share his unique perspective on the significance of the MESSENGER mission. Find out more about Professor Strom through this previously featured story: here..
Anyone near a computer during MESSENGER's flyby encounter can watch the planned observations unfold with simulated views of Mercury as seen via MESSENGER's two cameras by accessing the Mercury Flyby Visualization Tool, available at Flyby-Information/encounters/.
As the flyby continues to approach, additional information and features will be available online at Flyby-Information.html. Following the flyby, be sure to check back frequently to see the latest released images and science results!
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and after flybys of Earth, Venus, and Mercury will start a yearlong study of its target planet in March 2011. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery -class mission for NASA.
MESSENGER Only One Week from Mercury - January 7, 2008
MESSENGER's mid-December trajectory correction maneuver (TCM-19) went so well that the mission's design and navigation teams have decided that a TCM scheduled for January 10 will not be needed.
"Cancellation of this maneuver is a demonstration of the near-perfect execution of TCM-19 just prior to the start of the holiday season," says Mission Systems Engineer Eric Finnegan of the Johns Hopkins University Applied Physics Laboratory in Laurel, Md.
On January 9, MESSENGER's Mercury Dual Imaging System cameras will begin gathering pictures of Mercury as the probe zeros in on the planet. "With just one week to go before the flyby, the spacecraft is on target to encounter the planet at an altitude of 202 kilometers," Finnegan says. "All subsystems and instruments are operating nominally and configured for the start of the flyby sequence, except for the Mercury Laser Altimeter and part of the Gamma-Ray Spectrometer, which we'll turn on just before the flyby."
Over the next week, the team will make final flyby preparations and upload the final command sequences for the encounter.
"We are about to visit Mercury for the first time in more than 30 years, and we can't wait," says MESSENGER Principal Investigator Sean Solomon of the Carnegie Institution of Washington. "In addition to providing the critical gravity assist that will move MESSENGER along its path toward Mercury orbit insertion in March 2011, this flyby will let us see parts of Mercury never before viewed by spacecraft. We'll be making close-in observations of the composition of Mercury's surface and atmosphere, and we'll be probing deeper into the planet's magnetosphere than we've ever been. We expect many surprises."
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and after flybys of Earth, Venus, and Mercury will start a yearlong study of its target planet in March 2011. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery -class mission for NASA.
MESSENGER ZEROS IN ON MERCURY (December 19, 2007)
MESSENGER Completes Fifty Percent of Cruise Phase (November 19, 2007)
NASA Selects 23 Participating Scientists for MESSENGER Mission to Mercury (November 16, 2007)
Sun Cuts into MESSENGER's Dance around the Solar System (October 30, 2007)
Critical Deep-Space Maneuver Targets MESSENGER for Its First Mercury Encounter (October 17, 2007)
MESSENGER Team Wraps Up Radio Science Test (September 27, 2007)
MESSENGER Approaches Two Billion Miles! (September 12, 2007)
MESSENGER TO FEEL THE HEAT DURING FIRST "HOT" PERIAPSIS (August 31, 2007)
Happy Anniversary, MESSENGER! (August 3, 2007)
SEE MESSENGER's "FAREWELL TO VENUS" VIDEO (July 23, 2007)
CATCH MERCURY BEFORE DAWN ON JULY 20 (July 18, 2007)
MESSENGER Team Releases First Images From Venus 2 Flyby (June 14, 2007)
MESSENGER Makes Its Debut in the Smithsonian Museum (June 7, 2007)
MESSENGER Completes Second Flyby of Venus, Makes Its Way toward First Flyby of Mercury in 33 Years (June 5, 2007)
Watch Venus And Mercury This Week (And Imagine Messenger Flying By Venus) (June 1, 2007)
NASA TO PREVIEW MERCURY MISSION'S FLIGHT PAST VENUS (May 30, 2007)
MESSENGER ZEROS IN ON VENUS (May 25, 2007)
MESSENGER PI DISCUSSES SIGNIFICANCE OF NEWS THAT MERCURY HAS MOLTEN CORE (May 2, 2007)
MESSENGER LINES UP FOR SECOND PASS AT VENUS (May 2, 2007)
MESSENGER COMPLETES FORTY PERCENT OF CRUISE PHASE (April 2, 2007)
MESSENGER GEARING UP TO UNDERSTAND MERCURY'S MAGNETOSPHERE (March 19, 2007)
PRIMING INSTRUMENTS TO MAP MERCURY'S CRUST (February 20, 2007)
MESSENGER LINES UP FOR ITS SECOND VENUS FLYBY (December 2, 2006)
A MESSENGER SCIENCE TEAM MEMBER GETS A PREVIEW OF DISCOVERIES TO COME (November 10, 2006)
Upcoming Mercury/Sun Transit Whets the Appetite for MESSENGER Discoveries (November 6, 2006)
MESSENGER Completes Venus Flyby (October 24, 2006)
MESSENGER Tweaks Its Route to Mercury (September 15, 2006)
Happy Anniversary, MESSENGER! (August 3, 2006)
MESSENGER Flips Sunshade Toward the Sun (June 21, 2006)
MESSENGER Passes the Billion-Mile Mark! (March 24, 2006)
MESSENGER Lines Up for Venus Flyby (February 22, 2006)
MESSENGER Engine Burn Puts Spacecraft on Track for Venus (December 12, 2005)
MESSENGER Team Prepares for December Maneuver (November
11, 2005)
Movie Headlines MESSENGER Earth Flyby Gallery (August
26, 2005)
MESSENGER Completes Successful Earth Swingby (August 2, 2005)
MESSENGER Lines Up for Earth Swingby (July
21, 2005)
MESSENGER Executes Successful Flyby Test (July 5, 2005)
MESSENGER Sets Course for Earth Flyby (June 23, 2005)
MESSENGER Peeks at Earth (May 31, 2005)
MESSENGER Antenna Gains from Teamwork (April 27, 2005)
An Energetic Checkout (April 18, 2005)
MESSENGER Deploys Magnetometer, Flips Sunshade Toward Sun (March
8, 2005)
Planning for the Flip (March 1, 2005)
Staring at a Supernova (February
14, 2005)
Heading Back (February
7, 2005)
Planning Ahead (January 31, 2005)
Looking Ahead (January 10, 2005)
Power Play (December 20, 2004)
Three
for Three (November
18, 2004)
Maneuver
Keeps MESSENGER on Track (September
24, 2004)
Blazing
Thrusters (August
24, 2004)
Checkout
Time (August
10, 2004)
We
Have Liftoff! (August
3, 2004)
Launch
Reset for August 3 (August
2, 2004)
Going,
Going, Gone! (July 27, 2004)
MESSENGER
on the Launch Pad (July 21, 2004)
Next
Stop: The Launch Pad (July 19, 2004)
NASA
Sending a MESSENGER to Mercury (July 15, 2004)
Fill ‘er
Up! (July 9, 2004)
Upon
Reflection... (July 2, 2004)
MESSENGER
Launch Set for August 2 (June 29, 2004)
Vaughn
Named Engineer of Year (June 29, 2004)
Closing
Out (June 22, 2004)
On
Again (June 11, 2004)
Awaiting
the Big Push (June 3, 2004)
Taking
Commands (May 21, 2004)
Monthly
Cleaning (May 7, 2004)
MESSENGER
Team Member Wins Presidential Award (May
5, 2004)
Clear
Connection (April
29, 2004)
Undercover
Operations (April 23, 2004)
Communications
from the Cape (April 15, 2004)
The
Layered Look (April 9, 2004)
On
and Off (April 2, 2004)
MESSENGER
Launch Rescheduled (March 24, 2004)
MESSENGER's
Lifeline (March 18, 2004)
Another
Big Move! (March 12, 2004)
MESSENGER
Arrives (March 10, 2004)
MESSENGER
Ships to the Cape (March 9, 2004)
Out
of the Oven (March 5, 2004)
Home
Stretch (February 23, 2004)
The
Camera Takes Aim (February 11, 2004)
MESSENGER's
Heartbeat (February 6, 2004)
MESSENGER
Roast (January 30, 2004)
MESSENGER
Uncovered (January 22, 2004)
Spin
Cycle (January 15, 2004)
MESSENGER
Gets an Earful (January 7, 2004)
Keeping
MESSENGER Cool (December 30, 2003)
MESSENGER
Prepped for Prelaunch Tests (December 19, 2003)
MESSENGER
on the Move! (December 19, 2003)
Meeting
a Powerful Challenge (December 12, 2003)
In
the Swing (December 5, 2003)
Taking
Charge (November 26, 2003)
Test
Fire (November 19, 2003)
Up
or Down? (November 13, 2003)
Cosmic
Collisions (November 6, 2003)
Square
and Plumb (October 31, 2003)
Simulating
Space (October 24, 2003)
Status
Report: MESSENGER Aims for May Launch Date (October
21, 2003)
MESSENGER
Phones Home (October 16, 2003)
An
Instrumental Milestone (October 7,
2003)
Portable
Sun (October 3, 2003)
A
High-Tech Rain Coat (September 24,
2003)
Scanning
the Stars (September 17, 2003)
MESSENGER
Weighs In (September 4, 2003)
MESSENGER's
Eyes (August 28, 2003)
A
Clean Purge (August 19, 2003)
Spacecraft
in a Suitcase (August 14, 2003)
A Powerful
Move Forward (August 11, 2003)
Eyeing the
Field (August 1, 2003)
Schedule
Drivers (July 25, 2003)
MESSENGER's
Laser in Line for Installation (July 18, 2003)
A Powerful
Drive (July 10, 2003)
Heating Up (June
27, 2003)
MESSENGER Puts
on a MASCS (June 5, 2003)
Keeping Clean
in the Cleanroom (May 28, 2003)
Testing Time (May
20, 2003)
The 2003 Mercury
Transit (May 7, 2003)
MESSENGER Assembly
Under Way (March 12, 2003)
MESSENGER's
Propulsion System Is a Go (January 31, 2003)
MESSENGER Cleared
to Build Spacecraft (March 29, 2002)
NASA Gives
Official Nod to First Mercury Orbiter (June 7, 2001)
NASA SELECTS MESSENGER (July 1999)