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UARS WEEKLY STATUS REPORT - 4 June 2004
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SOLSTICE
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SOLSTICE continues to perform nominally, taking solar data on all
available orbital tracking periods. This week we received about 57% of
each day's data amounting to nearly 527 minutes of solar observing time
per day.
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SUSIM
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SUSIM successfully gathered its daily mid (1.1 nm) resolution, MgII,
occultation, solar pointing offset, and continuous monitoring scans
for periods of UARS real-time telemetry or onboard tape recording.
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PEM
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Nothing received.
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HALOE
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Nothing received.
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MLS
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Nothing received.
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HRDI
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Nothing received.
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MPG
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The MPG continues to serve as the point-of-contact for UARS
instrument operations in support of the Science Traceability
Mission of UARS.
Daily processing of instrument Daily Activity Plans continues
with no problems.
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CDHF
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Nothing received.
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FOT
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REPORTING PERIOD
This report covers 22 May 2004 (Orbit 69465, GMT Day 143) through
28 May 2004 (Orbit 69570, GMT Day 149).
SPACECRAFT OPERATION
The observatory is now in Reverse Flight (Northern Hemisphere viewing)
and is performing nominally under two-battery operations. The
instrument operational changes were:
INSTRUMENT OPERATIONAL CHANGES
Instrument Time Orbit Comment
HRDI 145/1250 69503 POWER ON F/T
The beta angle ranged between the angles of 30.1 degrees to 36.3
degrees for this report period. The beta angle is now decreasing
towards a minimum angle of 0 degrees on 06 June 2004 (DOY 158).
Spacecraft battery 1, 2, and 3 performance monitoring continues.
Battery 1 remains OFF the charge relay. Battery 2 and Battery 3 are
currently maintaining greater than 23.6 V end-of-night (EON) load bus
voltage. Battery temperatures are stable with a temperature delta
between Battery 2 and Battery 3 of 0.96 to 1.29 degrees C. Additional
battery performance data for each battery on 21 May and 28 May 2004
are provided in Appendix D.
The clock error ranged from -01.5 to -11.8 msec during this report
period. Clock rate adjustments are listed in Appendix C.
All instrument and subsystem engineers were advised on the initial
excursion of ALERTS or Out-Of-Limits conditions detected by the FOT
for this report. A summary is listed below and the details of ALERT
and Out-Of-Limits occurrences are listed in Appendix B.
OUT-OF-LIMITS = 00
ALERTS = 00
The following real-time command sheets were executed for the listed
operational element(s) during this report period (see Appendix A).
FOT = 04
HRDI = 01
UARS Anomaly Reports initiated during this report period are listed in
Appendix E and summarized below.
FOT = 05
Three (3) Anomaly Reports remained OPEN at the end of this report
period (see Appendix E).
GROUND SYSTEM OPERATION
Five (5) operational support problems occurred this period. Anomaly
Reports are included in Appendix E.
The data loss calculations are no longer being supplied by Data
Capture Facility (DCF).
OTHER SIGNIFICANT EVENTS
UARS SATELLITE OPERATIONS
This week UARS experienced an anomaly in the yaw reaction wheel. At
147/1651 Z a red alarm tripped indicating a FSW flag for a failed
reaction wheel had been set. Spacecraft telemetry showed that it was
the yaw wheel and that the spacecraft was now in three-wheel control.
The flight software calculates the estimated momentum loss on the
wheel and compares it to the measured loss. If they don't agree for
three samples in a row then the FSW automatically removes the suspect
wheel, commands three-wheel control and sets the flag to indicate a
problem with the wheel. This is exactly what happened during this
anomaly and the spacecraft maintained attitude throughout this
transition.
Analysis of the data showed that the yaw wheel had spun down in a
controlled manner, which indicated that the yaw wheel was healthy and
the problem was in the wheel momentum sensor or tachometer. It was
determined that this was a momentary glitch in the tachometer reading
and that four-wheel control should be reactivated. The recovery
procedure was tested and the yaw wheel was put back in the loop at
149/2336 Z. The FOT will continue to monitor this closely and will
attempt to recreate the momentary glitch on the simulator next week.
This test would normally have been done before the reactivation of the
wheel, but it was critical to get the wheel back into the loop, so
another occurrence would not cause the loss of the spacecraft.
On Monday, May 17 2004 VT-6 was commanded to return the differential
voltage to nominal levels. Within two orbits this change did exactly
that, and the differential voltage was back to between 30 and 60 mV.
The VT-6 level was maintained until Tuesday, May 25 2004 at which time
the nominal VT-5 mode was commanded. No sign of the high differential
voltage was seen after the change back to VT-5. This was the first
time VT-6 had to be commanded outside the yaw time frame so the FOT
will continue to monitor this closely.
MEETINGS
-The FOT attended a meeting with the HRDI team on 26 May 2004 to
discuss the analysis done on pointing issue. No conclusions have been
drawn as of yet, but more data is being collected and analyzed.
-The FOT held an anomaly review meeting on 27 May 2004 to discuss the
status of the yaw wheel anomaly and determine the next course of
action.
FUTURE SIGNIFICANT EVENTS
The next UARS Yaw slew is scheduled for 06 June 2004 (DOY 158). This
maneuver will be a Reverse to Forward Flight maneuver (Southern
Hemisphere viewing).
Attachments: Appendix A, Real-time Command Sheets
Appendix B, Out-Of-Limits & ALERT Occurrences
Appendix C, Clock & Solar Array Rate Corrections
Appendix D, UARS Battery Performance Data
Appendix E, UARS Anomaly Reports
APPENDIX A
REAL-TIME COMMAND SHEETS
Week ending 28 May 2004
ORBIT AOS NO. SUBSYS REASON
----- --- --- ------ ------
69465 143/0024 04-148 OBC/CLK CLK ADJ FR 20.6 TO 0.0 MSEC/DAY
69503 145/1250 04-149 HRDI POWER ON F/T
69520 146/1510 04-150 MPS VT 6 TO VT 5
69564 149/1341 04-151 OBC MEM MONITOR (REACTION WHEELS)
69570 149/2323 04-152 MACS YAW WHEEL BACK ON
APPENDIX B
OUT-OF-LIMITS & ALERTS OCCURRENCES
Week ending 28 May 2004
The following Out-Of-Limits occurrences were detected:
MNEMONIC STATE DESCRIPTION ORBITS
-------- ----- ----------- ------
OBSRWFZ R-LO YAW REACTION WHEEL 69543
The following ALERT occurrences were detected:
MNEMONIC DESCRIPTION ORBITS
-------- ----------- ------
-None this report period.
APPENDIX C
CLOCK & SOLAR ARRAY RATE CORRECTIONS
Week ending 28 May 2004
CLOCK DRIFT RATE ADJUSTMENTS
ORBIT TIME CLOCK RATE CHANGE
----- ----- -----------------
69465 143/0024 CLK ADJ FR 20.6 TO 0.0 MSEC/DAY
APPENDIX D
UARS BATTERY PERFORMANCE DATA
Week ending 28 May 2004
21 May 2004 - GMT Day 142 Beta = 36.2 deg, SA Pos = 269 deg
DIFF V (mV) TEMP (C) CURR (amp) EON V AVE C/D AVE
BAT MAX/MIN MAX/MIN MAX/MIN MIN RATIO DOD(%)
--- ------- -------- ---------- ----- ------- ------
1 -700.0/-700.0 -2.42/-3.68 +00.0/+00.0 07.0 0.00 0.0
2 +11.2/-33.6 +6.11/+5.14 +26.4/-14.4 26.6 1.03 20.0
3 +33.6/-44.8 +5.14/+3.87 +25.6/-14.4 26.4 1.03 19.6
28 May 2004 - GMT Day 149 Beta = 30.1 deg, SA Pos = 269 deg
DIFF V (mV) TEMP (C) CURR (amp) EON V AVE C/D AVE
BAT MAX/MIN MAX/MIN MAX/MIN MIN RATIO DOD(%)
--- ------- -------- ---------- ----- ------- ------
1 -700.0/-700.0 -2.73/-3.99 +00.0/+00.0 07.0 0.00 0.0
2 +44.8/-16.8 +6.44/+5.15 +27.2/-13.6 23.8 1.03 20.6
3 +67.2/-22.4 +5.15/+4.19 +26.4/-13.6 23.7 1.02 20.3
V/T LEVEL CHANGES
ORB# AOS TIME LVL FR-TO
----- -------- ---------
69520 142/1510 LV6 -> LV5
APPENDIX E
UARS ANOMALY REPORTS
Week ending 28 May 2004
NEW ANOMALY REPORTS GENERATED
AR NO. SUBSYS ORBIT TIME CDS PROBLEM/DATA LOSS
------ ------ ----- ---- --- -----------------
04-024 FOT 69469 143/0604 30832 Generic Late Acquisition
04-024 FOT 69497 145/0633 30832 Generic Late Acquisition
04-028 FOT 69532 147/1030 35958 No TDRSS Uplink
04-029 FOT 69543 148/0405 N/A Yaw Wheel Failure
04-030 FOT 69549 148/1343 35971 Minor Frame Dropouts
ANOMALY CLOSURE INFORMATION RECEIVED
AR NO. SUBSYS ORBIT TIME CDS PROBLEM/DATA LOSS
------ ------ ----- ---- --- -----------------
04-028 FOT 69532 147/1030 35958 No TDRSS Uplink
04-029 FOT 69543 148/0405 N/A Yaw Wheel Failure
04-030 FOT 69549 148/1343 35971 Minor Frame Dropouts
ANOMALY INVESTIGATION REPORTS GENERATED
AIR NO. SUBSYS ORBIT TIME CDS PROBLEM/DATA LOSS
------ ------ ----- ---- --- -----------------
-None this report period.
OPEN ANOMALY REPORTS
AR NO. SUBSYS ORBIT TIME CDS PROBLEM/DATA LOSS
------ ------ ----- ---- --- -----------------
04-024 FOT See List May 04 30832 Generic Late Acquisition
04-028 FOT 69532 147/1030 35958 No TDRSS Uplink
04-030 FOT 69549 148/1343 35971 Minor Frame Dropouts