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MESSENGER Mission News
March 19, 2012

MESSENGER Completes Primary Mission at Mercury, Settles in for Another Year
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."

Updated: MESSENGER Mercury Orbit Insertion Animation

With more than 99% of Mercury's surface imaged under similar illumination and viewing conditions, and with final spacecraft performance and final spacecraft orbit data available, MESSENGER's mission design team has updated the animation of MESSENGER's Mercury orbit insertion (MOI) maneuver. The largest and most important propulsive maneuver of the mission, MOI used more than 31% of the total propellant to transition the spacecraft's orbit center from the Sun to Mercury. About 2.5 weeks after MOI, after sufficient opportunity to monitor spacecraft health, temperature, and functionality, the primary science phase of the mission began.

This updated animation includes Mercury surface images from MESSENGER and a few extremely small areas with images from Mariner 10 flybys of Mercury in 1974 and 1975. "This animation features the best reconstructed orientation of the spacecraft, renderings of thruster flames as they occurred each second of MOI, as well as other details about the progress and orbit location relative to Mercury," says MESSENGER Mission Design Lead Engineer Jim McAdams.

The new MOI animation and a counterpart from March 2011 may be viewed near the end of the animations listed on http://messenger.jhuapl.edu/the_mission/ani.html, and also by clicking "animation" on http://messenger.jhuapl.edu/the_mission/gallery.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 entered orbit about Mercury on March 17, 2011 (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.

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