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After launch on a Delta 7925
(a Delta II Lite launch vehicle with nine strap-on solid-rocket
boosters) and a 10 month cruise phase, the Mars Global Surveyor
was inserted into an elliptical capture orbit at 01:17 UT
12 September 1997.
The Mars Global Surveyor mission
was designed to use the technique of "aerobraking" for the
first time as a mission-critical step. Aerobraking had been
successfully demonstrated in the final days of the 1988 Magellan
mission to Venus. MGS would begin in a highly-elliptical orbit
and use its solar panels to resist against the Martian atmosphere
as it dipped into it during the low point of its orbit. Panels
were installed at the ends of the solar panels to increase
drag on the spacecraft during aerobraking.
However, a problem arose when
the latch on one of the solar panels appeared to crack, and
the panel hinged itself past its designed position. Mission
operators had to design an aerobraking procedure that was
less stressful on the cracked solar panel. As a result, aerobraking
took much longer than anticipated. Originally, the mapping
phase was to begin in the spring of 1998, but because of the
delay did not begin until over a year later on April 4th,
1999. Due to the longer aerobraking phase, the mission was
able to return some science results and images of Mars during
a few brief hiatuses from aerobraking.
The craft has made discoveries
about volcanism on Mars, and has taken the best pictures yet
of Martian features like volcano Olympus Mons. Mapping of
the Martian surface will take one Martian year, or 687 days.
Once complete, scientists and mission planners will have a
first-class resource -- a complete high-resolution surface
map of Mars with topographical details -- for scientific exploration
and future missions.
The Mars Global Surveyor mission
cost about $154 million to develop and build and $65 million
to launch.
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