UARS Weekly Status Report

26 December 1997





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                UARS WEEKLY STATUS REPORT - 26 Dec 1997

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***********
SOLSTICE
***********

SOLSTICE continues to operate normally, collecting solar observations on every
orbit and stellar calibration observations when possible.

***********
SUSIM
***********

Nothing received.

***********
PEM
***********

     The PEM zenith spectrometers were active from December 4 through
December 7.  PEM produced energy deposition profiles from electron and 
proton precipitation from spectrometer data.

     PEM is awaiting evaluation by GSFC of its proposed activation procedure.
The minimal configuration for PEM AUX activation is the zenith VMAG, MEPS1, 
MEPS2, and HEPS1 units, only.  This configuration is driven by the capabilities 
of the spacecraft OBC and may increase if OBC program area increases.  PEM 
activation is proposed to be OBC driven when there exists plenty of power to 
operate PEM.  It is anticipated that the OBC will activate PEM on the daylight 
portions of every orbit.

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HALOE 
***********

Nothing received.

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MLS
***********

Nothing received.

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HRDI
***********

Nothing received.

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WINDII
***********

Nothing received.

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MPG
***********

Routine processing of instrument Daily Activity Plans continues
with no problems.  The MPG continues to assist the Project
Scientist with the scheduling of instrument operations.

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CDHF
***********

Nothing received.
                  
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FOT
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REPORTING PERIOD

This report covers 12 December 1997 (Orbit 34178, GMT Day 346) through 19 
December 1997 (Orbit 34282, GMT Day 353).


SPACECRAFT OPERATION

The observatory is now in Forward Flight (Southern Hemisphere viewing) and is 
performing nominally under two-battery operations.  The instrument operational 
changes were:

         INSTRUMENT OPERATIONAL CHANGES

  Instrument      Time      Orbit     Comment
     PEM       347/0058     34178     AXIS on
     HALOE     348/2326     34207       Off
     PEM       350/2340     34237       Off

The beta angle reached a minimum angle of 0.0 degrees on 17 December 1997 (DOY 
351).  The beta angle is now increasing toward a maximum angle of 34.0 degrees 
on 01 January 1998 (DOY 001).

A Reverse-to-Forward Yaw Around maneuver (number 64) was successfully executed 
in Orbit 34246 at 14:41:26 UTC on 17 December 1997.  The SSPP Instruments 
(ACRIM, SOLSTICE, and SUSIM) were enabled.  Due to the SA position at 269 
degrees, the effective night length of the spacecraft after the maneuver was 48 
minutes.  Post maneuver analysis of data indicate that during the Yaw Around, 
the end-of-night load bus voltage was 24.8 volts and the average depths of 
discharge (DODs) on Batteries 2 and 3 were approximately 23.0 and 22.0 percent 
respectively.

Two additional SSPP Solar Offset experiments were performed this week - UTC 
Days 348 and 349.  These experiments were identical to the normal solar offset
that is performed on a weekly basis.

On-Board Computer (OBC) system table definitions for tables 42 & 43 (star 
tracker alignment & update filter status flags) were modified on Monday, 15 
December 1997 (orbit 34220, 349/20:17:52 UTC).  These changes were required to 
allow clearing of update filter status telemetry flags which are sometimes set 
during the yaw maneuvers (this functionality was inadvertently eliminated from 
the update filter software included in flight software version 62).  No code 
changes were required, but due to updated system table definitions, the 
on-orbit flight software is now designated version 62, revision C (V62C).  An 
operational database change was also required to support this revision (see 
Ground System Operation).

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 25.1 V end-of-night (EON) load bus voltage.  Battery 
temperatures are stable with a temperature delta between Battery 2 and Battery 
3 of 1.3 degrees C.  Additional battery performance data for each battery on 
13 December 1997 and 19 December 1997 are provided in Appendix D.

The clock error ranged from -10.0 to +9.7 msec during this report period.  
Clock rate adjustments are listed in Appendix C.

On the 15 December 1997, a Rgyro glitchS occurred on the UARS spacecraft at 
approximately 349/00:18 UTC.  This resulted in an abrupt spacecraft pitch 
movement of about 200 arc seconds error which slowly recovered to normal by 
349/04:00 UTC.  It took approximately four hours of star tracker and fine sun 
sensor readings to bring the 200 arc second reference error back to normal and 
allow the OBC reported attitude errors to again give accurate spacecraft 
attitude telemetry.  The last reported gyro glitch took place on 23 January 
1996, and was discussed in UARS Anomaly Investigation Report AIR 96-010.  
Further investigation into this gyro glitch continues.

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.

%     ALERTS            =     00
%     OUT-OF-LIMITS     =     09

The following real-time command sheets were executed for the listed operational 
element(s) during this report period (see Appendix A). 

%     FOT     01
%     HALOE   01
%     HRDI    03
%     PEM     02
%     SUSIM   01
%     WINDII  01

UARS Anomaly Reports initiated during this report period are listed in Appendix 
E and summarized below.

%     FOT     01

TRANSPONDER FREQUENCIES:
     Transponder A:  97/343 - 2287.497007
     Transponder B:  97/344 - 2287.499121


GROUND SYSTEM OPERATION

One (1) operational support problem(s) occurred this period. Anomaly Reports
are included in Appendix E.

The data loss calculations supplied by Data Capture Facility (DCF) from mission 
start through UTC Day 97/352 show the observatory data loss to be 20 hours, 41 
minutes, 12.916 seconds (no change).  This is a 0.0378 percent data loss which 
equals a 99.9622 percent data capture for the mission.

The FOT is still working out the details of participating in the IP return-link 
telemetry test that the network is conducting.

Operational Database version 65 was released for use on Monday, 15 December 
1997 (orbit 34220, 349/20:09:00 UTC).  This release was scheduled to 
correspond with changes to on-orbit system table definitions for tables 42 & 
43 (star tracker alignment & update filter status flags) made during the same 
contact (see Spacecraft Operation).

Flight Dynamics Facility (FDF) delivered a new Star Catalog to the FOT on 18 
December.  The new catalog was required to fix the invalid precession rate for 
star 48000001.  After the FOT verifies the integrity of the new catalog, it 
will be configured for operational use on the Command Management System (CMS).

No testing of the new CMS software release (R7B1V2) occurred this week.

UARS Test and Training Simulator (UTTS) testing of Q-channel data flow was 
conducted on 17 and 18 December 1997.  Only a few OBC dumps were successfully 
collected.  On 17 December, the Q-channel driver did not indicate any data 
flow.  NASCOM and DOC saw clock data but no data across the Q-channel line.  
The driver was switched and the first OBC data dump was received.  However, 
following attempts to dump the OBC failed.  On 18 December, after 
reconfiguring the CDH module the first dump of the OBC was good.  However, 
subsequent dumps were very sporadic and with many errors in the dump 
comparisons.  ATSC has been informed of the problem.

Operational processing of level-0 telemetry analysis files on the UMPGAL 
computer (new MPG Alpha machine) was started on Monday, 15 December 1997.  SSAI 
corrected the problem with user account quotas on the UMPGAL computer, allowing 
the successful processing of level-0 files on this machine.  However, network 
problems continued with transfer of the level-0 files from CDHF to UMPGAL, 
preventing fully successful processing of these files.  On Thursday, 18 
December 1997, the FOT modified level-0 processing jobs on CDHF and UMPGAL to 
perform verification checks on file transfer completion, and to perform 
redundant transfers if necessary.  Since then the level-0 processing jobs have 
run successfully on UMPGAL in parallel with identical processing on CDHF.


OTHER SIGNIFICANT EVENTS

FOT Memo 97-051, RUARS Flight Software Version 62 Update Filter Changes,S was 
released in response to numerous requests for this information from Code 512.

Monitoring of the magnetic field model performance continues.

FOT continues to improve a Power Profile for UARS based on the current status 
of the Modular Power System.

FOT continues to support the new UARS ground system re-engineering effort.


MEETINGS

No UARS Battery telecon was held this week.  The next telecon has not been 
scheduled.


FUTURE SIGNIFICANT EVENTS

The next UARS Yaw Around Maneuver is currently scheduled for 16 January 1998 at 
016/13:25:14 UTC.

The UARS orbit altitude is dropping slowly and a drag makeup orbit adjust will 
probably be required in mid-1998.


FACILITIES

no change


PERSONNEL CHANGES

no change


Attachments:  Appendix A, Real-time Commands 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 19 December 1997

ORBIT       AOS          NO.     SUBSYS         REASON
-----       ---          ---     ------         -------  
34178     347/0058     97-622   PEM/AXIS   Power ON
34187     347/1524     97-623     HRDI     Heater delay to 150 amp. mins. 
34190     347/2001     97-624     HRDI     Heater delay to 50 amp. mins. 
34203     348/1706     97-625    SUSIM     Sec. Detector Off
34207     348/2326     97-626    HALOE     Power OFF
34215     349/1214     97-627     HRDI     Heater delay to 200 amp. mins. 
34220     349/2009     97-628     OBC      New system table 42 & 43 defs.
34235     350/2013     97-629    WINDII    Heater delay to 350 amp. mins. 
34237     350/2340     97-630     PEM      Power OFF


_______________________________________________________________

                               APPENDIX B
                   OUT-OF-LIMITS & ALERTS OCCURRENCES
                      Week ending 19 December 1997

MNEMONIC      STATE      DESCRIPTION                       ORBITS
---------     -----      ------------                      ------
HRIFESURVTMP  Y-HI     HRDI IFE SURVIVAL TEMP        34179,83-4,98-99,214
HRRADTEMP     Y-HI     HRDI RADIOMETER TEMP          34179
WIEUTEMP      Y-LO     WINDII ELECTRONICS UNIT TEMP  34183-34282
OBSSOC2       Y-LO     Battery 2 Current SOC         34185-219
OBSVLBEON     Y-LO     Load Bus Volts at EON         34189-206
OBSBATVEON3   Y-LO     Battery 3 voltage at EON      34188-206
OBSBATVEON2   Y-LO     Battery 2 voltage at EON      34190-206
QTSISAIF      Y-LO     SSPP Baseplate by SISA I/F    34192,258,61-65,73-82
SOSTMPRNTRN   Y-LO     Temperature Entrance          34273


The following ALERT occurrences were detected:

MNEMONIC                DESCRIPTION                        ORBITS
---------               ------------                       ------
 (none)



                                APPENDIX C
                 CLOCK & SOLAR ARRAY RATE CORRECTIONS
                       Week ending 19 December 1997

                      CLOCK DRIFT RATE ADJUSTMENTS

     ORBIT              TIME              CLOCK RATE CHANGE
     -----              ----              -----------------
   no changes                         remained at 00.0 msec/day


_______________________________________________________________

                              APPENDIX D
                    UARS BATTERY PERFORMANCE DATA
                       Week ending 19 December 1997

     13 Dec 1997 - GMT Day 347 Beta = 18.6 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  +728.0/+728.0  -3.05/-4.62  +0.0/ +0.0    18.7    0.000     0.0
2   +33.6/ -22.4  +6.44/+5.15 +32.4/-15.2    25.1    1.024    22.9
3  +112.0/  +0.0  +4.83/+3.87 +31.2/-15.6    25.1    1.022    22.2

     19 Dec 1997 - GMT Day 353 Beta =  4.8 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  +728.0/+728.0  -3.05/-4.62   +0.0/ +0.0   18.7    0.000     0.0
2   +44.8/ -22.4  +5.47/+4.51  +31.2/-13.6   25.1    1.023    21.8
3  +112.0/  +0.0  +4.51/+2.92  +29.6/-14.4   25.1    1.022    21.1


     V/T LEVEL CHANGES
ORB#     TIME      LVL FR-TO
-----  --------  ----------
      no changes     
               

_______________________________________________________________
                                   APPENDIX E
                              UARS ANOMALY REPORTS
                            Week ending 19 December 1997

  AR NO.   SUBSYS       ORBIT      TIME       TTR      PROBLEM/DATA LOSS
  ------   ------       -----      ----       ---      -----------------
  97-124    FOT         34210    349/0430    14170     Generic Late


            ANOMALY CLOSURE INFORMATION RECEIVED
  AR NO.   SUBSYS       ORBIT      TIME       TTR      PROBLEM/DATA LOSS
  ------   ------       -----      ----       ---      -----------------
      None this report period


          ANOMALY INVESTIGATION REPORTS GENERATED
  AIR NO.  SUBSYS       ORBIT      TIME       TTR      PROBLEM/DATA LOSS
  -------  ------       -----      ----       ---      -----------------
     None this report period



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