From: Jet Propulsion Laboratory
Posted: Wednesday, June 6, 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
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.
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.
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.
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).
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