Two weeks after recovery from safe mode and the restoration of standard operations, the Mars Global Surveyor spacecraft continues to perform excellently as it cruises toward an encounter with the red planet later this summer. Currently, Surveyor is operating in a quiet state with no major activity sequences programmed in the onboard computer. The flight team will transmit the next major sequence load toward the end of the month.
On Tuesday of this week, the flight team sent a few commands to Surveyor that activated gyroscope #2 for a period of one hour. Several weeks ago, this gyro was automatically powered down when its usage of electrical current exceeded a preset limit. Although gyros help the spacecraft keep track of its pointing orientation in space, there was no loss of control because Surveyor's #1 and #3 gyros seamlessly assumed the function of the powered down unit.
During the one hour of operation, the amount of electrical current used by gyro #2 was well below the level that would have resulted in an automatic power down. Although the gyro is functional, the project management has decided to leave it powered off. Flight software code is being developed that will autonomously activate gyro #2 in the unlikely event that an anomalous condition precludes the usage of either the #1 or #3 gyro. This new software will be transmitted to Surveyor in a few weeks.
The only other notable activity this week occurred late Thursday. That evening, the flight team transmitted a short series of commands to Surveyor that modified the onboard software. These minor changes will ensure that the infinite-loop condition that resulted in safe mode entry will never happen again.
After a mission elapsed time of 211 days from launch, Surveyor is 137.88 million kilometers from the Earth, 24.04 million kilometers from Mars, and is moving in an orbit around the Sun with a velocity of 22.57 kilometers per second. This orbit will intercept Mars 97 days from now, slightly after 6:00 p.m. PDT on September 11th (01:00 UTC, September 12th). All systems continue to be in excellent condition.
Status report prepared by:
Office of the Flight Operations Manager
Mars Surveyor Operations Project
NASA Jet Propulsion Laboratory
California Institute of Technology
Pasadena, CA 91109