Mars Global Surveyor Status Report 6 June 2001
Wednesday, June 6, 2001 (DOY 150/19:00:00 to DOY 157/19:00:00 UTC)
Launch / Days since Launch = Nov. 7, 1996 / 1673 days
Start of Mapping / Days since Start of Mapping = April 1, 1999 / 797 days
Total Mapping Orbits = 10,043
Total Orbits = 11,726
Recent Events:
Background Sequences – The spacecraft is operating nominally in performing
the beta-supplement daily recording and transmission of science data. The
mm144 sequence executed successfully from 01-151 (5/31/01) through 01-153
(6/02/01). The mm145 sequence has performed well since it started on 01-154
(6/03/01). It terminates on 01-157 (6/06/01). The mm146 sequence,
successfully uplinked on 01-156 (6/05/01), begins executing on 01-158
(6/07/01).
Other – Ten more Roll Only Targeted Observations (ROTOs) were performed
since the last report. MGS has completed a total of 117 ROTOs to date.
Spacecraft Health:
All subsystems report good health and status.
The Sun Monitor Ephemeris fault protection is disabled to prevent another
C-Mode entry due to sun-sensor shadowing by the HGA. Sun-sensor shadowing is
the most likely cause of the 5/2/01 entry into C-Mode. The shadowing was
caused by a combination of planetary geometry and beta-supplement HGA
positioning. The 35 degree Solar Panel offpoint caused the SAM sun-sensor
instead of the SAP sun-sensor to be selected for sensing sun position.
Flight software could not accurately compute sun position when the SAM
sun-sensor became shadowed by the HGA. Other fault protection routines
continue to protect MGS from losing its attitude knowledge.
Uplinks:
There have been 13 uplinks to the spacecraft during the past week, including
instrument command loads, the background sequences cited above, and ROTO
mini-sequences mz104, mz105, & mz106. There have been 5,419 command files
radiated to the spacecraft since launch.
Upcoming Events:
DOY 01-172 (6/21/01) marks the end of the beta-supplement phase and the
beginning of the nominal mapping phase of the mission. Planetary and orbital
geometry will allow the HGA to auto-track the Earth without impacting the
HGA boom. Nominal mapping sequences will not be as command intensive as the
beta-supplement sequences. Therefore, 28-day background sequences will be
the norm instead of the 3 and 4 day beta-supplement sequences.
Another MGS Mars Relay On-orbit UHF Test will be conducted with Stanford
University between 01-177 (6/26/01) and 01-179 (6/28/01). MOLA Polar Scans
are scheduled for 01-193 (7/12/01) and 01-194 (7/13/01).
