MEDIA RELATIONS OFFICE
JET PROPULSION LABORATORY
CALIFORNIA INSTITUTE OF TECHNOLOGY
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
PASADENA, CALIF. 91109. TELEPHONE (818) 354-5011
http://www.jpl.nasa.gov

       An error in the software commands sent to Mars Global Surveyor to turn its solar arrays to the proper Sun angle for the start of aerobraking caused significant discharge of the spacecraft's batteries and, subsequently, sent it into a "contingency" mode. In this mode, all non-essential onboard spacecraft operations are temporarily suspended as the spacecraft awaits new commands from the ground.

       Fault protection software detected the low battery charge and aborted the sequence before Global Surveyor began its maneuver at 3:30 a.m. Pacific Daylight Time. This stopped initiation of the aerobraking maneuver.

       "We will be able to recharge the battery later today and resume aerobraking probably on Wednesday," said Glenn E. Cunningham, manager of the Mars Multimission Operations team and Mars Global Surveyor project manager.

       The spacecraft remains stable, with communications being performed using Surveyor's low-gain antennas. The flight team at Lockheed Martin Astronautics, Denver, will spend the next several days evaluating onboard hardware changes that may have occurred as a result of the low battery charge and subsequent contingency mode.

       A new schedule for returning Global Surveyor to its proper aerobraking configuration will be announced as soon as possible, but will not impact the aerobraking phase or the start of the science mapping mission in April 1999.