MESSENGER Mission News
September 15, 2006
MESSENGER Tweaks Its Route to Mercury
The MESSENGER trajectory correction maneuver 11 (TCM 11) on September 12 lasted just under four minutes and adjusted the spacecraft's velocity by about 1.68 meters per second (5.5 feet per second). The short-duration maneuver kept MESSENGER on track for next month's Venus flyby.
Tuesday's maneuver started at 7 p.m. EDT; mission controllers at The Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Md., verified the start of the maneuver about 12 minutes later, when the first signals indicating thruster activity reached NASA's Deep Space Network tracking station outside Canberra, Australia.
While MESSENGER has used all 17 of its thrusters in completing several successful maneuvers, TCM 11 was the first course correction to require two sets of primary thrusters. Part A of the maneuver began at 7 p.m. EDT and lasted 23 seconds; Part B began at 7:10 p.m. and lasted 202 seconds.
Operators moved MESSENGER in two perpendicular movements during the maneuver - instead of on a straight path - to protect the spacecraft's heat-sensitive electronics from direct sunlight. The movements kept the sunshade in position to block the blinding sunlight, which warms the spacecraft nearly three times faster now than if MESSENGER were orbiting Earth.
The next TCM - the last chance for mission controllers to tweak the spacecraft's route prior to the Venus flyby - will take place no later than October 12. For graphics of MESSENGER's orientation during the maneuver, visit the "Trajectory Correction Maneuvers" section of the mission Web site.
MESSENGER Team to Share Notes with Venus Express
The primary goal of MESSENGER's October flyby of Venus is to receive a gravity assist that will put it on course to its final destination: Mercury. None of its instruments will be powered on near the time of closest approach, because Venus will be on the opposite site of the Sun from the Earth and the spacecraft will be out of direct communication for approximately three weeks.
MESSENGER will fly by Venus a second time, on June 6, 2007, and during that event all payload instruments will be trained on the planet before, during, and after closest approach. The MESSENGER team is working closely with the team operating Europe's Venus Express mission to take advantage of the fact that two spacecraft will be in the vicinity of Venus at the same time.
The European Space Agency (ESA) launched the Venus Express mission in November 2005; the spacecraft entered Venus orbit in April and in June began its primary science mission to unveil the source of the planet's dense, turbulent and toxic atmosphere. Venus Express carries seven primary instruments, many of which were spares left over from previous ESA missions, such as the agency's Mars Express and comet-bound Rosetta programs.
For the October flyby, MESSENGER mission managers will exchange trajectory information with the Venus Express team. For the second flyby in June 2007, a range of coordinated observations of Venus is now being planned.
"As it is with any mission to the other planets in the solar system, when you have the opportunity to make multiple observations from different spacecraft at the same time you are giving yourself the opportunity to learn more than you would learn from either one operation on its own," says Ralph McNutt, MESSENGER's project scientist, from the Applied Physics Laboratory.
For information about Venus Express, go online to http://sci.esa.int/science-e/www/area/index.cfm?fareaid=64.
MESSENGER Added to Solar System Simulator Web Site
This summer the MESSENGER spacecraft was added to NASA Jet Propulsion Laboratory's (JPL) Solar System Simulator Web site. This highly capable, award-winning site features numerous options for viewing the planets, 24 selected planetary satellites, and the solar system using a variety of fields of view. The orbits of eleven interplanetary spacecraft are also featured.
JPL uses the Solar System Simulator as the sole tool for its "Where is Cassini?" feature (see http://saturn.jpl.nasa.gov/operations/present-position.cfm). The Solar System Simulator features the full-mission reference trajectory (reconstructed orbit as well as predicted orbit through the nominal end of mission) for the MESSENGER spacecraft.
The see the MESSENGER feature, go online to http://space.jpl.nasa.gov, and highlight "MESSENGER spacecraft," within the "Show me" prompt.
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 Aug. 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 the Discovery-class mission for NASA.