[meteorite-list] MESSENGER Primed for Mercury Orbit

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Tue, 15 Mar 2011 13:01:32 -0700 (PDT)
Message-ID: <201103152001.p2FK1WlC013331_at_zagami.jpl.nasa.gov>

The Johns Hopkins University Applied Physics Laboratory
Office of Communications and Public Affairs
Laurel, Maryland
Media Contact: Paulette W. Campbell
(240) 228-6792
Paulette.campbell at jhuapl.edu

March 15, 2011

FOR IMMEDIATE RELEASE

MESSENGER PRIMED FOR MERCURY ORBIT

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 on at around 9 p.m. EDT on Thursday, March 17.

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."

###

The Applied Physics Laboratory, a not-for-profit division of The
Johns Hopkins University, meets critical national challenges through
the innovative application of science and technology. For more
information, visit http://www.jhuapl.edu.
Received on Tue 15 Mar 2011 04:01:32 PM PDT