[meteorite-list] MESSENGER Completes Primary Mission at Mercury, Settles in for Another Year

[Ron Baalke]

http://messenger.jhuapl.edu/news_room/details.php?id=197

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  <http://www.sciencemag.org/content/early/recent> 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."

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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.
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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.