Summary:
The performance of the Mars Global Surveyor spacecraft continues as
expected after two weeks of low activity and reduced monitoring. Other
than the planned MOLA (Mars Orbiter Laser Altimeter) Earth scans from the
Cruise 3 activities, the S/C (spacecraft) has remained in Array Normal Spin
for this period. Thermal, Power and Telecommunications performance remains
well within expectations. The Cruise 3 sequence executed on the S/C as
expected however, the MOLA Earth scan was not successful due primarily to
cloudy weather at Goddard Space Flight Center. Station or data transmission
problems resulted in a loss of about 20 minutes of playback data. These data
will be recovered via a playback scheduled for later in the week. Following
the MOLA scans, the S/C quietly provided Magnetometer data for the remainder
of the holiday period.
Y Solar Array Deployment:
There were no efforts toward S/C solar array trouble shooting during this
period. The last set of "wiggle" tests provided a good baseline and
validated the dynamics model that is being used to design further attempts
to latch the panel.
Attitude Control:
Performance of the AACS (Attitude & Articulation Control System) subsystem
has been excellent. Star processing performance has been nominal with stable
gyro bias estimates.
Following the MOLA Earth scan the S/C return to ANS converged well. The
control errors were small but the knowledge errors were large enough to
miss the Earth according to MOC (Mars Orbiter Camera) instrument personel.
Attitude knowledge inaccuracies are still being investigated.
Thermal:
The S/C thermal state continues to be within expected limitations.
Telecom:
The telecommunications subsystem performance continues to be excellent..
All uplinks were accomplished without incident and as expected.
Preparations were finalized for the KaBLE HGA (High Gain Antenna) check-out.
This test will provide valuable Ka-Band performance data and contribute information
regarding HGA pointing accuracy for X and Ka Bands. The average uplink AGC
was -119 dBm and the downlink AGC was -145 over the LGA (Low Gain Antenna)
for the period.
Power:
Excellent power subsystem performance continues. Still no evidence of
solar array degradation.
Propulsion:
The propulsion subsystem performance continues excellent performance.
Analysis and trending shows tanks pressures as expected.
Command & Data Handling, Payload Distribution & Flight Software:
Excellent C&DH (Command & Data Handling) subsystem performance continues.
Two more single event upsets occurred over the holiday period. An apparent
flight software error
was observed during the past two weeks. The STAREX word switched from a
F000 state (which is nominal) to a F010 state. The additional bit shows
"SIS interrupted". However, other telemetry proves that SIS is not
interrupted. Apparently a momentum unload caused the "SIS interrupted" bit
to get set and a FSW bug prevented it from being reset. A 1 Hz process and
2 Hz process appear to be out of sync. FSW experts believe there is no
impact, and SIS continues to operate nominally.
Sequence and Command Activities:
The nominal Cruise 3 (C3) sequence was uplinked and executed. All sequence
activity occurred as expected. An aerobraking re-plan kickoff meeting was
held to examine the issues related to performing aerobraking using the -Y
solar array in its present un-latched condition. The C4 product
development is nearly complete for pass 2. Other than the uplink of the C3
sequence and the KaBLE mini-sequence, the only commands radiated over the
holiday period were the usual NO-OP commands to reset command loss fault
protection and update of the star catalogs and ephemeris files.
The System Test Lab (STL) suffered a failure and made it impossible to test
the KaBLE mini-sequence. The lab apparently failed a power supply in one
of the interface unit's VME chassis. This problem will be repaired later
this week.
No additional ISAs were identified this week.
Ground Data Systems:
No problems have been noted this week with ground systems.