MESSENGER Update - March 24, 2006

http://messenger.jhuapl.edu/news_roo..._03_24_06.html

Status Report: MESSENGER Passes the Billion-Mile Mark!
March 24, 2006

On March 23 MESSENGER reached the one-billion mile mark, placing the
spacecraft about one-fifth of the way toward its destination to orbit
Mercury. On that same day, in the early morning hours (UTC), the
spacecraft's distance from the Sun was about the same as the Earth's
distance to the Sun. "One billion miles and the team and spacecraft are
doing well," says Mission Operations Manager Mark Holdridge of the
Johns
Hopkins Applied Physics Laboratory (APL), where the spacecraft is
operated and where it was designed and built.

For a complete look at MESSENGER's journey through the inner solar
system, visit the Mission Design section of the Web site at
http://messenger.jhuapl.edu/the_miss...on_design.html. To see
where MESSENGER is now, visit
http://messenger.jhuapl.edu/whereis/index.php.

Flop Positions Spacecraft toward the Sun

The MESSENGER spacecraft performed its final "flop" maneuver for the
mission on March 8, pointing the back side of the spacecraft to the Sun
until June 2006. This rotation about the X-axis is performed whenever
the solar distance increases beyond approximately 0.95 astronomical
units (AU), nearly the distance between the Earth and the Sun. At this
distance, the solar arrays do not generate enough power to operate all
spacecraft components simultaneously, including instruments and
heaters.
The "flop" is performed to heat the back side of the spacecraft with
the
Sun. A "flip" maneuver reverses the effect of the "flop" maneuver by
pointing the sunshade toward the Sun. This solar heating reduces the
need for multiple onboard heaters, providing the necessary power until
the spacecraft is closer to the Sun again. Previous flip, flop, and
flip
maneuvers were performed on March 8, 2005, June 14, 2005, and September
7, 2005. The spacecraft is scheduled to flip back toward the Sun on
June 21.

MESSENGER's Science Team Web Site Is Up!

Even though the MESSENGER spacecraft is years away from entering its
final destination of orbiting Mercury, the mission Science Team is
already very busy collecting scientific data and sharing it with the
larger scientific community. Those plans and results are now available
on the team's new Web site; http://messenger.jhuapl.edu/soc/index.html.
Check it out now to view images and data returned by the MESSENGER
instruments from the successful Earth flyby on August 2, 2005, the
first
of six planetary flybys in the mission plan; see a bibliography of
publications by project team members about the MESSENGER mission and
related Mercury science, dating back to when NASA first selected the
MESSENGER mission in 1999; and access a list of recent presentations
about MESSENGER and related science issues made by Science Team
members.

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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 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.