Mars Global Surveyor Status Report 28 June 2000
(DOY 173/19:00:00 to DOY 180/19:00:00 UTC)
Launch / Days since Launch = Nov 7, 1996 / 1330 days
Start of Mapping / Days since Start of Mapping = April 1, 1999 / 454 days Total Mapping Orbits = 5846
Total Orbits = 7449
Recent Events:
Background Sequences — The mm050 and mm051 Solar Conjunction sequences were uplinked successfully and the MOC was turned off by commands in the mm049 sequence. The mm050 sequence became active on 00-175 (6/23/00). We are now in the Solar Conjuction phase of the mission.
Spacecraft Health:
All subsystems report nominal health. We are seeing more noise in the downlink signal as the Sun-Earth-Mars angle decreases. This is expected. The Sun-Earth-Mars angle will reach a minimum of 0.87 degrees on 00-183 (7/1/00). The downlink signal will gradually improve with time beyond that date.
Uplinks:
Only one file was uplinked to the spacecraft during the last week. It was the mm051 sequence. Total command files radiated to the spacecraft since launch is 4717.
Upcoming Events:
We expect to return to normal spacecraft configuration and beta-supplement command sequences starting with the mm052 sequence on 00-195 (7/13/00). Until then, we will monitor spacecraft health and the actual vs. predicted timing of orbital events. The spacecraft attempts to contact Earth during three of the twelve orbits each day during the Solar Conjunction period. When the downlink signal is good, we receive engineering telemetry and the actual Mars equator crossing time for that orbit. We compare the actual equator crossing time with the predicted equator crossing time to determine the accuracy with which we placed spacecraft maneuvers. We expect the accuracy of our orbital timing to degrade with time. Tracking the rate at which the timing degrades will help us ensure the spacecraft health during the next few weeks. We are prepared to cancel or rebuild stored sequences if timing degradation reaches unacceptable levels. Presently our predictions deviate from actual orbit timing by less than six seconds. This is well within the established parameters (Gee, I sound like Data). Once the spacecraft emerges from Solar Conjunction and we are able to obtain two-way Doppler tracking data, our orbital timing estimates will return to normal.