Mars Global Surveyor Status Report 24 May 2000
Wednesday, May 24, 2000 (DOY 131/19:00:00 to DOY 145/19:00:00 UTC)
Launch / Days since Launch = Nov 7, 1996 / 1295 days
Start of Mapping / Days since Start of Mapping = April 1, 1999 / 419 days
Total Mapping Orbits = 5418
Total Orbits = 7021
Recent Events:
Background Sequences — The spacecraft continues to operate nominally in performing the beta-supplement daily recording and transmission of science data.
The following background sequences executed successfully: mm038 from 00-132 (5/11/00) through 00-135 (5/14/00); mm039 from 00-136 (5/15/00)
through 00-138 (5/17/00); mm040 from 00-139 (5/18/00) through 00-142 (5/21/00); and mm041 from 00-143 (5/22/00) through 00-145 (5/24/00). The
mm042 sequence was successfully uplinked on 00-144 (5/23/00) and will begin executing on 00-146 (5/25/00).
Science Experiments – Three science experiment campaigns took place during the past two weeks. They were Bistatic Radar, MOLA Off-NADIR Polar Scans,
and Radio Science Occultation Egress Scans. Commands for the Bistatic Radar experiment were included in the mm038 sequence as part of DOY 135
activities. Commands for the MOLA Off-NADIR Polar Scans composed the mz051 mini-sequence. They executed over 11 consecutive orbits on DOY 138
and DOY 139. Finally, MGS performed Radio Science Occultation Egress Scans on DOY 141,142, and 143 according to the mz052 mini-sequence. Overall,
spacecraft performance during all experiments was nominal. The following paragraphs provide additional information regarding AACS performance.
In the MOLA experiment, we used the same CSA offset quaternions as the previous two polar opportunities. The SARBES (Starex reset) command was
eliminated from this sequence and replaced with a general memory load of high rate gyro bias estimates and a separate software command to load the high rate
steady state gyro biases. We also retained the divided North and South Pole slews implemented with the last MOLA polar opportunity. We are happy to report
that the Starex problems observed in previous MOLA polar experiments have disappeared. Starex performance was completely, totally, and utterly nominal.
Slew performance was superb, as it was for the previous polar experiments.
For the first time during a Radio Science Occultation Egress experiment, we used an Off-NADIR pointing scheme. AACS performance proved nominal,
comparing well with predicts. Again, Starex performed superbly, converging in 10 stars. We successfully used the same method of gyro bias loading in the
Radio Science experiment that we used in the MOLA Polar Scan experiment. Preliminary results indicate that the science teams received useful data during
these experiments. Therefore, we plan to use the same spacecraft pointing and sequence development techniques for future MOLA and Radio Science
experiments.
Spacecraft Health:
All subsystems report nominal health.
Uplinks:
There have been 28 uplinks to the spacecraft during the last two weeks, including new star catalogs and ephemeris files, instrument command loads, and the
background sequences cited above. Total command files radiated to the spacecraft since launch is 4666.
Upcoming Events:
Normal beta-supplement sequences are planned between now and Solar Conjunction. We are in the final stages of Solar Conjunction planning. The mm050
sequence will cover the Solar Conjunction period between 6/21/00 and 7/12/00.
