PART 1: Happy Holidays
PART 2: There's still time to participate in the Scavenger Hunt!
PART 3: Mars Global Surveyor flight status report
PART 4: Subscribing & Unsubscribing: How to do it!

HAPPY HOLIDAYS!

A special thank you to everyone who has participated in Live From Mars
this year! Your involvement in Web chats, student activities and in
sending in email questions is what has made this project work!

This will be the last weekly updates until after winter break. Web chats
will also resume after the holidays. The LFM team looks forward to working
with you again in January!

May the lights of this holiday season light up your life!

THERE'S STILL TIME TO PARTICIPATE IN THE SCAVENGER HUNT

To participate in the Weather Worlds Scavenger Hunt answer the 25
questions at: http://passporttoknowledge.com/lfm/events/wwhuntqs.html

The class that answers the most questions correctly in each level
(elementary, middle and high school) will be the winner. A random drawing
will be held in case of a tie at any or all levels. All answers must be
sent by 12 a.m., PST, Tuesday, December 23, 1997.

MARS GLOBAL SURVEYOR FLIGHT STATUS REPORT

Friday, December 12, 1997

A dust storm raging across the southern hemisphere of Mars has slowed the
progress of Mars Global Surveyor's aerobraking over the last two weeks.
Although the altitude of the spacecraft's atmospheric passes lies well
above the height of any potential encounter with dust, the storm traps
heat and causes a tremendous increase in air pressure at all altitudes.

The possible occurrence of these storms was expected because Mars is
approaching summer in the southern hemisphere, and this time of year marks
the start of the traditional dust storm season. As a consequence of these
historical trends and data returned from Surveyor's scientific
instruments, the flight team's atmospheric advisory group issued a
forecast in late November of a possible onset of dust storms.

Surveyor's first direct encounter with the effect of these storms occurred
early on the morning of November 28 when the spacecraft
encountered a 120% increase in atmospheric density during an aerobraking
pass on orbit #51. Shortly afterward, Flight Operations Manager Joe Beerer
gave the order for the spacecraft to perform a short firing of its
thruster rockets to raise the altitude of the orbit's low point. Later
that morning, Project Manager Glenn Cunningham ordered a second maneuver
as a precautionary measure after receiving a storm warning from the
atmospheric advisory group.

In total, the two post-Thanksgiving maneuvers raised the altitude of the
orbit's low point by 4.35 miles (7 km). This increase was designed to
lower the air pressure experienced by the spacecraft by a factor of 2.7 on
subsequent passes through the atmosphere. Since then, Surveyor has been
aerobraking at altitudes up to 6.2 miles (10 km) higher than the baseline
plan. The higher aerobraking altitudes resulted in a lower air pressure
and guarded against further atmospheric blooming due to dust storm
activity.

According to Dr. Richard Zurek of the atmospheric advisory group, the dust
storm once covered an area equal to the southern Atlantic Ocean, but now
appears to be fading in intensity. The flight team is continuing to
monitor conditions in the Martian atmosphere and has begun to return the
spacecraft to its normal pace of aerobraking. However, despite the slower
than normal progress over the last two weeks, aerobraking operations
during this time has trimmed nearly 1240 miles (2000 km) from the orbit's
high point, and decreased the period of revolution around Mars by 1.9
hours.

After a mission-elapsed time of 400 days from launch, Surveyor is 192.72
million miles (310.15 million kilometers) from the Earth and in an orbit
around Mars with a high point of 24,468 miles (39,378 km), a low point of
79.0 miles (127.1 km), and a period of 29.6 hours. The spacecraft is
currently executing the P63 command sequence, and all systems continue to
perform as expected. The next status report will be released on Wednesday,
December 24.

SUBSCRIBING & UNSUBSCRIBING: HOW TO DO IT!

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