QUESTION:
I've read that Mars Global Surveyor will fire its rockets for approximatetly
12 minutes and go into orbit around Mars. It will then dip into the upper
Martian atmosphere and round out its orbit.

How do you know what part of the spacecraft to dip into the atmosphere? How
will it be configured as it skims the atmosphere? What happens if the
atmosphere is more dense than you calculate because of unplanned things like
sunspots or some other astrological event?

ANSWER from Charles Whetsel on September 15, 1997:
The Mars Global Surveyor spacecraft will be placed on a trajectory which
places the entire spacecraft just slightly below the top of the planet's
atmosphere on every orbit (for about 400 orbits) between September 1997 and
January 1998.  The solar arrays are configured in a "swept-back"
configuration (like a shuttle-cock).  Throughout aerobraking, the MGS
instrument suite, along with the support of earth-based observatories, will
be monitoring the Martian atmosphere to detect any changes in the
atmosphere.