[meteorite-list] MESSENGER Gets Closer to Mercury than Ever Before

[Ron Baalke]

http://messenger.jhuapl.edu/news_room/details.php?id=259

MESSENGER Mission News
July 28, 2014

MESSENGER Gets Closer to Mercury than Ever Before

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."

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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
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.