Mars Global Surveyor Status Report 31 July 2002
(DOY 205/19:00:00 to DOY 212/19:00:00 UTC)
Launch / Days since Launch = Nov. 7, 1996 / 2093 days
Start of Mapping / Days since Start of Mapping = April 1, 1999 / 1218 days
Total Mapping Orbits = 15,179
Total Orbits = 16,862
Recent Events:
Background Sequences – The spacecraft is operating nominally in performing the beta-supplement daily recording and transmission of science data. The mm198 sequence executed successfully from 02-206 (7/25/02) through 02-208 (7/27/02). The mm199 sequence has performed well since it started on 02-209 (7/28/02). It terminates on 02-213 (8/01/02). The mm200 sequence, successfully uplinked on 02-212
(7/31/02), begins executing near the end of day on 02-213(8/01/02).
Other – Three Roll Only Targeted Observations (ROTOs) were performed successfully by the mz192 mini-sequence. MGS has completed 285 ROTOs to date.
The MOC instrument was turned off on 02-212 (7/31/02) in preparation for solar conjunction. Its replacement heaters will keep it thermally safe until it is turned back on following conjunction.
Spacecraft Health:
Spacecraft subsystems report good health and status. The signatures of the Payload Data Subsystem (PDS) software resets from several weeks ago are similar to two PDS software resets that occurred in 1999. PDS software developer’s assessed the root cause for the 1999 resets to be the reprogramming of science data bandwidth. Bandwidth originally designed for the Mars Orbiter GRS and PMIRR instruments was reallocated to increase MGS MOC and TES bandwidth since GRS and PMIRR were not being flown on MGS. This reprogramming altered the PDS’ finely tuned timing and marginal dynamic memory reserve such that (occasional) process memory starvation became possible. PDS’ inability to complete a process due to insufficient memory is one of several triggers for a software reset.
Uplinks:
There have been 10 uplinks to the spacecraft during the past week, including instrument command loads, the mz192 ROTO mini-sequence, and the mm199 andmm200 background sequences. 6,908 command files have been radiated to the spacecraft since launch.
Upcoming Events:
MM201, the second of two solar conjunction background sequences will be uplinked on 02-214 (8/02/02). It covers the later part of solar conjuction through 02-231 (8/19/02). Downlink during solar conjunction shall be real time, low rate data only with no playbacks. Recording will be done throughout the sequences on SSR 2A only, should a playback of recent data be necessary. The Command Loss Timer (CLT) will be set to 18 days. There will be no ranging during these sequences. The telecom subsystem will be configured back to normal Beta Supplement operations at the end of sequence mm201.
Another Flex Modes Test of the solar arrays and HGA gimbal will be performed because of data losses during the playback. We are looking at opportunities during the transition between the end of solar conjunction and the start of nominal beta-supplement sequences.
ROTOs are suspended until after solar conjunction.
