MSOP-MGS Status Reports for 2000

Launch / Days since Launch = Nov 7, 1996 / 1141 days
Start of Mapping / Days since Start of Mapping = April 1, 1999 / 265 days
Total Mapping Orbits = 3535
Total Orbits = 5217

Recent Events:

The mm010 sequence continues executing nominally the daily science record and playback events. The mm010 sequence runs through January 12.

The MPL landing site imaging campaign has begun. Currently 16 of 19 planned targeted scans across the predicted 1-sigma MPL landing ellipse have been executed. Unfortunately no obvious signs of the lander or its parachute have been found at this time. Note that the definition of the landing ellipse continues to change as additional atmospheric data from MGS is factored in. As a result the imaging mosaic currently begin generated may not reflect the latest landing site knowledge. The spacecraft has behaved almost flawlessly in performing the imaging scans. The only off-nominal performance of note was some difficulty in with star processing upon completion of one of the scans. A ground command was set to perform a bias reset, which was successful in getting the star processing software to converge properly, before any autonomous fault protection action was taken. The remaining three scans are currently on-board the spacecraft in the mz032 sequence and will have all finished executing by this Friday afternoon.

In addition to the MPL scans, an additional special targeted opportunity to image the Mars Pathfinder landing site will be performed Sunday December 26 at 09:18 UTC. The data from the MPF scan will be used as comparison for what to look for in the MPL landing site images, with regards to possibly seeing the parachute and backshell.

HGA Anomaly:

The HGA inner gimbal angle continues to decrease and is currently at 57.9 degrees. The inner gimbal angle will continue decreasing, reaching the location of the gimbal obstruction at 41.5 deg in early February. Work has begun again on the development and validation of the HGA beta supplement operations plan, which will be used to perform mapping operations for the rest of the nominal mapping mission. STL testing of the transition products and new mapping sequences will begin Thursday December 23.

Spacecraft Health:

All subsystems are reporting nominal health. Power reports that battery 2 switched from VT curve 2 to VT curve 1 as a result of performing the MPL scans. This was expected and is resulting in slightly higher battery 2 temperatures. Upon completion of the MPL and MPF scans, we may reset the VT curve back to VT2, although the nominal trend may soon have both batteries on VT1 anyhow.

Uplinks:

There have been 34 uplinks to the spacecraft during the last week, including new star catalogs and ephemeris files, the mz031 and mz032 MPL imaging mini-sequences. Total command files radiated to the spacecraft since launch is 4258.

Upcoming Events:

1) The mm011 sequence kickoff meeting is scheduled for January 4 2000.

Launch / Days since Launch = Nov 7, 1996 / 1134 days
Start of Mapping / Days since Start of Mapping = April 1, 1999 / 258 days
Total Mapping Orbits = 3449
Total Orbits = 5131

Recent Events:

The mm009 sequence continues executing nominally the daily science record and playback events. The mm009 sequence will run through Wednesday December 15, at which point the mm010 sequence will take over. Last week, a change request was approved for MGS to perform special targeted scans in order to obtain high-resolution MOC images of the MPL landing site. The mz030 mini-sequence will contain 10 imaging scans through December 19, with two to three imaging opportunities per day. The first of these imaging scans will be performed on Thursday December 16 at 13:38 UTC. Additional imaging will be performed next week through December 24. It is hoped that we will have successfully imaged most of the one-sigma landing ellipse by the end of this campaign. After the holidays, we will make a decision whether to continue these imaging scans in an attempt to fill in the entire three-sigma landing ellipse.

HGA Anomaly:

The HGA inner gimbal angle continues to decrease and is currently at 60.7 degrees. The inner gimbal angle will continue decreasing, reaching the location of the gimbal obstruction at 41.5 deg in early February. Over the last week, due to efforts to support imaging of theMPL landing site, work has been suspended on the new beta supplement mapping implementation. It is anticipated that this work will pick up again next week.

Spacecraft Health:

All subsystems are reporting nominal health.

Uplinks:

There have been 21 uplinks to the spacecraft during the last week, including new star catalogs and ephemeris files and the mm010 sequence. Total command files radiated to the spacecraft since launch is 4224.

Upcoming Events:

1) Final preparations of the mz030 mini-sequence to perform the MPL landing site imaging. Sequence is scheduled for uplink late Wednesday Dec 15, with the first image period on Dec 16 at 13:38:40 UTC.

Launch / Days since Launch = Nov 7, 1996 / 1127 days
Start of Mapping / Days since Start of Mapping = April 1, 1999 / 251 days
Total Mapping Orbits = 3363
Total Orbits = 5045

Recent Events:

Following the landing of the Mars Polar Lander (MPL) and the DS2 Mars Microprobes, MGS has been busy supporting the efforts to communicate with them via the Mars Relay UHF antenna. An on-board command sequence was loaded to MGS to manage the MR tones in support of attempted MPL UHF contacts. This sequence has been initiated several times by real-time command over the last few days and will probably be executed several more times as part of the contingency planning being done for MPL. The mz026, mz027 and mz028 sequences in support of the DS2 microprobes all executed normally but unfortunately nothing has been heard from them as well. Due to battery limitations on the probes, it is assumed that they have died and no further efforts will be taken to communicate with them.

It is anticipated that a request for MGS to image the landing site will be shortly forthcoming and will be a high priority item over the next week or two.

The mm009 sequence continues executing nominally the daily science record and playback events. The mm009 sequence will run through Wednesday December 15, at which point the mm010 sequence will take over.

HGA Anomaly:

The HGA inner gimbal angle continues to decrease and is currently at 62.8 degrees. The inner gimbal angle will continue decreasing, reaching the location of the gimbal obstruction at 41.5 deg in early February. Over the last week and a half, due to efforts to support MPL and DS2 both pre- and post- landing, work has been suspended on the new beta supplement mapping implementation. It is anticipated that this work will pick up again next week or the week after. Sufficient schedule margin exists to support current MPL contingency efforts.

Spacecraft Health:

A second PDS reset has recently occurred. The first occurred on November 26 and the second on December 5. We will look into this harder after contact with MPL is made or efforts to communicate with it have ceased. All other subsystems continue to report nominal status.

Uplinks:

There have been 47 uplinks to the spacecraft during the last week, including new star catalogs and ephemeris files, instrument command loads, and numerous MR mode commands in support of efforts to hear from MPL and the DS2 microprobes. Total command files radiated to the spacecraft since launch is 4203.

Upcoming Events:

1) Development of the next mapping sequence, mm010, begins December 2.

2) Targeted observations of the MPL landing site.

Launch / Days since Launch = Nov 7, 1996 / 1120 days
Start of Mapping / Days since Start of Mapping = April 1, 1999 / 244 days
Last Orbit Covered by this Report = 3277
Total Orbits = 4959
Total Mapping Orbits = 3277

Recent Events:

The mm009 sequence continues executing nominally the daily science record and playback events. The mm009 sequence will run through Wednesday December 15, at which point the mm010 sequence will take over.
The DS2 Mars Microprobes mini-sequences, used to sequence the Mars Relay (MR) commands for the over-flights of the two probes, were successfully uplinked Friday November 26. The mz026 mini-sequence is the nominal Mars sol 0 through 3 sequence. The mz027 and mz028 sequences are contingency sequences for probe 1 and 2 respectively, taking advantage of more frequent MGS over-flights than the mz026 nominal sequence. If successful contact is made with one or both probes the appropriate contingency sequence or sequences will be stopped by ground command. The MR was successfully powered on Monday November 29, completing the required uplinks necessary to support the DS2 mission.

HGA Anomaly:

The HGA inner gimbal angle continues to decrease and is currently at 65 degrees. The inner gimbal angle will continue decreasing, reaching the location of the gimbal obstruction at 41.5 deg in early February. Work continues on the implementation of the new mapping data collection and return plan that will maximize the science data return for the remainder of the nominal mapping mission. JPL has provided an engineering delivery of the update command blocks. Work is also proceeding well on the development of the automated mapping sequence generation tool. System level validation in the STL should begin in the next couple of weeks.

Spacecraft Health:

All other subsystems continue to report nominal status.

Uplinks: There have been 32 uplinks to the spacecraft during the last week, including new star catalogs and ephemeris files, instrument command loads, and the DS2 mini-sequences and MR turn on. Total command files radiated to the spacecraft since launch is 4156.

Upcoming Events:

1) Development of the next mapping sequence, mm010, begins December 2.

Launch / Days since Launch = Nov 7, 1996 / 1106 days
Start of Mapping / Days since Start of Mapping = April 1, 1999 / 230 days
Last Orbit Covered by this Report = 3105
Total Orbits = 4787
Total Mapping Orbits = 3105

Recent Events:

The mm008 sequence continues executing nominally and will continue execution through November 17. The mm009 sequence has been uplinked to the spacecraft and will begin execution Nov 18 at 00:00:00 UTC. Spacecraft Test Lab (STL) validation of the mini-sequences, which will command the Mars Relay (MR) in support of the DS2 microprobes mission on December 3, will begin Nov 18.

HGA Anomaly:

The HGA inner gimbal continues to decrease and is currently at 69.1 degrees. The inner gimbal angle will continue decreasing, reaching the location of the gimbal obstruction at 41.5 deg in early February. Work continues on the implementation of the new mapping data collection and return plan that will maximize the science data return for the remainder of the nominal mapping mission. The updated mapping command blocks have been released to JPL. Work is also proceeding well on the development of the automated mapping sequence generation tool. System level validation in the STL should begin in the next couple of weeks.

Spacecraft Health:

All other subsystems continue to report nominal status.

Uplinks:

There have been 15 uplinks to the spacecraft during the last week, including new star catalogs and ephemeris files, and instrument command loads. Total command files radiated to the spacecraft since launch is 4097.

Upcoming Events:

1) Power on of the MR is scheduled for November 29.

2) Validation of the DS2 MR mini-sequences, with uplink scheduled for early next week.

Launch / Days since Launch = Nov 7, 1996 / 1100 days
Start of Mapping / Days since Start of Mapping = April 1, 1999 / 224 days
Last Orbit Covered by this Report = 3032
Total Orbits = 4714
Total Mapping Orbits = 3032

Recent Events:

The mm008 sequence continues executing nominally and will continue execution through November 17. Development of the mm009 sequence has begun. Work has also begun on the development and validation of the mini-sequences required for MR commanding in support of the DS2 microprobes mission on December 3.
The change approved last week to update the sampling rate for critical spacecraft telemetry, that will allow us to more fully characterize and ascertain the cause of the HGA position error counts, has been uplinked to the spacecraft. At this time we have not had a repeat of the event with the new telemetry in place.

HGA Anomaly:

The HGA inner gimbal angle continues to decrease and is currently at 70.7degrees. The inner gimbal angle will continue decreasing, reaching the location of the gimbal obstruction at 41.5 deg in early February. Work continues on the design and implementation of a new mapping data collection and return plan that will maximize the science data return for the remainder of the nominal mapping mission. The updated mapping command blocks have been generated and will be released to JPL early next week so they can begin implementing them in the sequencing software. This will support the start of system level validation in the STL in the next few weeks.

Spacecraft Health:

All other subsystems continue to report nominal status.

Uplinks:

There have been 26 uplinks to the spacecraft during the last week, including new star catalogs and ephemeris files, and instrument command loads. Total command files radiated to the spacecraft since launch is 4082.

Upcoming Events:

1) Validation and uplink of the mm009 sequence November 15.

2) Validation and uplink of the DS2 MR mini-sequences.

Launch / Days since Launch = Nov 7, 1996 / 1093 days
Start of Mapping / Days since Start of Mapping = April 1, 1999 / 217 days
Last Orbit Covered by this Report = 2946
Total Orbits = 4628
Total Mapping Orbits = 2946

Recent Events:

The mm008 sequence continues executing nominally and will continue execution through November 17. Development of the mm009 sequence has begun. Work has also begun on the development and validation of the mini-sequences required for MR commanding in support of the DS2 microprobes mission on December 3.
It was reported last week that the HGA position error counts had stopped. Since then there have been several repeat occurrences of this event. A change has been approved to update the sampling rate for critical spacecraft telemetry that will allow us to more fully characterize and ascertain the cause of these counts.
A test to power on the Mars Relay and exercise several of the modes required for support of the DS2 microprobes and the Mars Polar Lander on December 3 and beyond was successfully executed over November 3rd and 4th . A team at Stanford supported the checkout by listening for the MR signal. As of now they are reporting that they were unsuccessful in their attempts to receive a signal. All indications from the MR housekeeping telemetry packets, transmitted in the MOC data, however, indicate that the MR performed as expected.

HGA Anomaly:

The HGA inner gimbal angle continues to decrease and is currently at 72.5 degrees. The inner gimbal angle will continue decreasing, reaching the location of the gimbal obstruction at 41.5 deg in early February. Work continues on the design and implementation of a new mapping data collection and return plan that will maximize the science data return for the remainder of the nominal mapping mission. STL (Spacecraft Test Laboratory) testing of a FSW patch to the HGA auto-track algorithm was successfully tested this week. The updated mapping command blocks have been generated and will be released to JPL early next week so they can begin implementing them in the sequencing software. This will support the start of system level validation in the STL in the next few weeks.

Spacecraft Health:

All other subsystems continue to report nominal status.

Uplinks:

There have been 26 uplinks to the spacecraft during the last week, including new star catalogs and ephemeris files, and instrument command loads. Total command files radiated to the spacecraft since launch is 4056.

Upcoming Events:

1) Validation and uplink of the mm009 sequence November 15.

2) Validation and uplink of the DS2 MR mini-sequences.

Launch / Days since Launch = Nov 7, 1996 / 1086 days
Start of Mapping / Days since Start of Mapping = April 1, 1999 / 210 days
Last Orbit Covered by this Report = 2860
Total Orbits = 4542
Total Mapping Orbits = 2860

Recent Events:

The mm008 sequence continues executing nominally and will continue execution through November 17. The HGA position error counts noted last week have not recurred since. At this time, no further action is being taken by the SCT to determine the cause of those events, due to priorities in preparing the MPL spacecraft for Mars landing on December 3. We will continue to watch for recurrence of these events and determine appropriate action at that time.

HGA Anomaly:

The HGA inner gimbal angle continues to decrease and is currently at 73.8 degrees. The inner gimbal angle will continue decreasing, reaching the location of the gimbal obstruction at 41.5 deg in early February. Work continues on the design and implementation of a new mapping data collection and return plan that will maximize the science data return for the remainder of the nominal mapping mission.

Spacecraft Health:

All other subsystems continue to report nominal status.

Uplinks:

There have been 32 uplinks to the spacecraft during the last week, including new star catalogs and ephemeris files, and instrument command loads. Total command files radiated to the spacecraft since launch is 4030.

Upcoming Events:

1) The mm009 sequence development kickoff meeting is scheduled for November 2, with uplink preliminary scheduled for November 15.

Launch / Days since Launch = Nov 7, 1996 / 1079 days
Start of Mapping / Days since Start of Mapping = April 1, 1999 / 203 days
Last Orbit Covered by this Report = 2774
Total Orbits = 4456
Total Mapping Orbits = 2774

Recent Events:

The mm008 sequence continues executing nominally and will continue execution through November 17. Over the last week there have been several HGA position error counts (35 counts on 10/14, 37 counts on 10/17, and 35 counts 10/21) associated with the start of the HGA rewinds that occur every orbit. We are currently analyzing the spacecraft telemetry to determine the cause of the "sticky" gimbals. In the meantime a change has been approved to increase the fault protection threshold to prevent the on-board redundancy management software from swapping to the B-side HGA gimbal drive electronics in response to this recent behavior.

HGA Anomaly:

The HGA inner gimbal angle continues to decrease and is currently at 74.9 degrees. The inner gimbal angle will continue decreasing, reaching the location of the gimbal obstruction at 41.5 deg in early February. Work continues on the design and implementation of a new mapping data collection and return plan that will maximize the science data return for the remainder of the nominal mapping mission.

Spacecraft Health:

All other subsystems continue to report nominal status.

Uplinks:

There have been 21 uplinks to the spacecraft during the last week, including new star catalogs and ephemeris files, and instrument command loads. Total command files radiated to the spacecraft since launch is 3998.

Upcoming Events:

1) The mm009 sequence development kickoff meeting is scheduled for November 2, with uplink preliminary scheduled for November 15.

Launch / Days since Launch = Nov 7, 1996 / 1072 days
Start of Mapping / Days since Start of Mapping = April 1, 1999 / 196 days
Last Orbit Covered by this Report = 2698
Total Orbits = 4371
Total Mapping Orbits = 2689

Recent Events:

The mm008 sequence continues executing nominally and will continue execution through November 17. Due to weather at the DSN stations and the increasing Earth to Mars range, there has been an increased number of lost data packets over the last week. The average data return during this period has been approximately 92.5 %. Previous averages have been in the upper 90% range. Due to the increasing Earth-Mars range, the baseline mission plan calls for decreasing the science playback and realtime rates from their high rates, 85333 and 80000 bps, respectively, to the middle rates, 42666 and 40000 bps, respectively, in the next sequence, mm009, scheduled to begin execution November 18.

HGA Anomaly:

The HGA inner gimbal continues to decrease and is currently at 75.9 degrees. The inner gimbal angle will continue decreasing, reaching the location of the gimbal obstruction at 41.5 deg in early February. Work continues on the design and implementation of a new mapping data collection and return plan that will maximize the science data return for the remainder of the nominal mapping mission.

Spacecraft Health:

All subsystems continue to report nominal status.

Uplinks:

There have been 22 uplinks to the spacecraft during the last week, including new star catalogs and ephemeris files, and instrument command loads. Total command files radiated to the spacecraft since launch is 3977.

Upcoming Events:

1) The mm009 sequence development kickoff meeting is scheduled for November 2, with uplink preliminary scheduled for November 15.

Launch / Days since Launch = Nov 7, 1996 / 1065 days
Start of Mapping / Days since Start of Mapping = April 1, 1999 / 189 days
Last Orbit Covered by this Report = 2603
Total Orbits = 4285
Total Mapping Orbits = 2603

Recent Events:

The mm007 sequence has completed execution. The mm008 sequence has been uplinked to the spacecraft and is now active as of Thursday October 7. The mm008 sequence is a six week long sequence and will continue to execute through November 17.

HGA Anomaly:

The HGA inner gimbal is currently at 76.19 degrees and is now coming back down. The maximum angle was 76.2 degrees, occurring late on DOY 279. The inner gimbal angle will continue decreasing, reaching the location of the gimbal obstruction at 41.5 deg in early February. Work is currently underway to implement a new mapping data collection and return plan to maximize our science data return for the remainder of the nominal mapping mission.

Spacecraft Health:

All subsystems continue to report nominal status.

Uplinks:

There have been 17 uplinks to the spacecraft during the last week, including the mm008 sequence, new star catalogs and ephemeris files, and instrument command loads. Total command files radiated to the spacecraft since launch is 3955.

Upcoming Events:

1) The mm009 sequence development kickoff meeting is scheduled for November 2, with uplink preliminary scheduled for November 15.

Launch / Days since Launch = Nov 7, 1996 / 1051 days
Start of Mapping / Days since Start of Mapping = April 1, 1999 / 175 days
Last Orbit Covered by this Report = 2432
Total Orbits = 4114
Total Mapping Orbits = 2432

Recent Events:

The mm007 sequence is executing nominally and will continue to control spacecraft mapping operations through October 6. Development of the mm008 sequence has begun and is scheduled to begin on 10/7.

HGA Anomaly:

The HGA inner gimbal is currently at 75.4 deg and will increase to a maximum of ~76 deg in early October, before coming back down to the location of the obstruction at 41.5 deg in early February. Work is currently underway to implement a new mapping data collection and return plan to maximize our science data return for the remainder of the nominal mapping mission.

Spacecraft Health:

All subsystems continue to report nominal status.

Uplinks: There have been 9 uplinks to the spacecraft during the last week, including new star catalogs and ephemeris files, and instrument command loads. Total command files radiated to the spacecraft since launch is 3923.

Upcoming Events:

1) Sequence mm008 development begins Tuesday Sept. 21 and goes active on 10/7/99.

Launch / Days since Launch = Nov 7, 1996 / 1044 days
Start of Mapping / Days since Start of Mapping = April 1, 1999 / 168 days
Last Orbit Covered by this Report = 2260
Total Orbits = 4028
Total Mapping Orbits = 2346

Recent Events:

The mm007 sequence is executing nominally and will continue to control spacecraft mapping operations through October 6.

HGA Anomaly:

The HGA gimbal is currently operational with full redundancy on side-A. The fault protection threshold for HGA stuck gimbal is at 25 seconds (50 counts).

Spacecraft Health:

All subsystems continue to report nominal status.

Uplinks: There have been 15 uplinks to the spacecraft during the last week, including new star catalogs and ephemeris files, and instrument command loads. Total command files radiated to the spacecraft since launch is 3914.

Upcoming Events:

1) Sequence mm008 development begins Tuesday Sept. 21 and goes active on 10/7/99.

Launch / Days since Launch = Nov 7, 1996 / 1037 days
Start of Mapping / Days since Start of Mapping = April 1, 1999 / 161 days
Last Orbit Covered by this Report = 2260
Total Orbits = 3942
Total Mapping Orbits = 2260

Recent Events:

The mm007 sequence is executing nominally and will continue to control spacecraft mapping operations through October 6.

HGA Anomaly: The HGA gimbal is currently operational with full redundancy on side-A. The fault protection threshold for HGA stuck gimbal is at 25 seconds (50 counts).

Spacecraft Health:

All subsystems continue to report nominal status.

Uplinks: There have been 10 uplinks to the spacecraft during the last week, including new star catalogs and ephemeris files, and instrument command loads. Total command files radiated to the spacecraft since launch is 3899.

Upcoming Events:

1) Sequence mm008 goes active on 10/8/99

Launch / Days since Launch = Nov 7, 1996 / 1030 days
Start of Mapping / Days since Start of Mapping = April 1, 1999 / 154 days
Last Orbit Covered by this Report = 2174
Total Orbits = 3856
Total Mapping Orbits = 2174

Recent Events:

The mm007 sequence has been controlling S/C activities since August 26. The new HGA gimbal operations utilized by this sequence has been successful in reducing the microphonics noise observed by the Thermal Emission Spectrometer (TES) instrument.

The first part of the 2-part Magnetometer calibration test was successfully completed on August 31. The S/C momentum wheels became saturated when counteracting the high rate motion of the panels which resulted in a temporary (~4°) S/C offpoint. Today's test (part 2) is underway and so far has shown no evidence of the momentum wheels saturation as seen before. This test is comprised of a series of solar array motions on the night side of the orbit that will be used to more fully characterize the magnetic signature of the spacecraft.
The Power subsystem noticed a drop in payload current loads this week, which was later attributed to a MOC subsystem reset which powered off the focus heaters. Commands were radiated to the S/C that restored the MOC configuration.

HGA Anomaly:

The HGA gimbal is currently operational with full redundancy on side-A. The fault protection threshold for HGA stuck gimbal is at 25 seconds (50 counts).

Spacecraft Health:

All subsystems continue to report nominal status.

Uplinks:

There have been 20 uplinks to the spacecraft during the last week, including the MAG calibration sequences, new star catalogs and ephemeris files, and instrument command loads. Total command files radiated to the spacecraft since launch is 3889.

Upcoming Events:

1) Sequence mm008 goes active on 10/8/99

Launch / Days since Launch = Nov 7, 1996 / 1023 days
Start of Mapping / Days since Start of Mapping = April 1, 1999 / 147 days
Last Orbit Covered by this Report = 2089
Total Orbits = 3771
Total Mapping Orbits = 2089

Recent Events:

The mm007 sequence has been controlling S/C activities since August 26. This sequence is the first stop the HGA auto-tracking during non-Earth communications periods to further reduce the microphonics noise observed by the Thermal Emission Spectrometer (TES) instrument. The three-stop solar array articulation scheme continues in this sequence and has provided an improvement in TES data quality.

Development of the special two-part Magnetometer (MAG) calibration sequence is complete and ready to be loaded for execution on the spacecraft August 31 and September 2. This test is comprised of a series of solar array motions on the night side of the orbit that will be used to more fully characterize the magnetic signature of the spacecraft.

HGA Anomaly: The HGA gimbal is currently operational with full redundancy on side-A. The fault protection threshold for HGA stuck gimbal is at 25 seconds (50 counts).

Spacecraft Health:

All subsystems continue to report nominal status.

Uplinks:

There have been 11 uplinks to the spacecraft during the last week, including the mm007 sequence, thruster accumulator reset, and instrument command loads. Total command files radiated to the spacecraft since launch is 3869.

Upcoming Events:

1) MAG calibration on Aug 30 and Sept 2.

Launch / Days since Launch = Nov 7, 1996 / 1016 days
Start of Mapping / Days since Start of Mapping = April 1, 1999 / 140 days
Last Orbit Covered by this Report = 2003
Total Orbits = 3685
Total Mapping Orbits = 2003

Recent Events:

The mm006 sequence is currently executing the daily science data collection and return and will continue execution through August 25. The mm007 sequence has been completed and will be uplinked Monday August 23. The mm007 sequence will initiate stoppage of the HGA auto-tracking during non-Earth communications periods as an additional change in nominal mapping operations to reduce microphonics noise in the Thermal Emission Spectrometer (TES) instrument.

Work continues on the development of a Magnetometer (MAG) calibration sequence to be executed on the spacecraft August 31. This test is comprised of a series of solar array motions on the night side of the orbit that will be used to more fully characterize the magnetic signature of the spacecraft.

HGA Anomaly:

The HGA gimbal is currently operational with full redundancy on side-A. The fault protection threshold for HGA stuck gimbal is at 25 seconds (50 counts).

Spacecraft Health:

All subsystems continue to report nominal status.

Uplinks:

There have been 13 uplinks to the spacecraft during the last week, including new star catalog and ephemeris files, and instrument command loads. Total command files radiated to the spacecraft since launch is 3858.

Upcoming Events:

1) MM007 sequence to be uplinked Monday Aug 23.

2) MAG calibration on Aug 31.

Launch / Days since Launch = Nov 7, 1996 / 1009 days
Start of Mapping / Days since Start of Mapping = April 1, 1999 / 133 days
Last Orbit Covered by this Report = 1918
Total Orbits = 3600
Total Mapping Orbits = 1918

Recent Events:

The mm006 sequence is currently executing the daily science data collection and return and will continue execution through August 25.

OTM-3 was successfully executed on Wed Aug 11 at 17:38:05 UTC. The OTM was designed to target a 50 km ground track repeat cycle. Preliminary Navigation team orbit determination analysis performed following the burn predicts a 50.4 km ground track repeat cycle. All spacecraft subsystems performed nominally during and after the burn.

On the orbit following the OTM, autonomous solar array tracking was terminated and the three part per orbit Solar Array motion command sequences were successfully initiated. Based on tests performed recently on the spacecraft, it is believed that this will significantly reduce the microphonics noise seen in the Thermal Emission Spectrometer (TES) instrument data.

Work continues on the development of a Magnetometer (MAG) calibration sequence to be executed on the spacecraft August 31. This test is comprised of a series of solar array motions on the night side of the orbit that will be used to more fully characterize the magnetic signature of the spacecraft.

The source of the "tiny gaps" that have regularly occurred in the high rate mapping telemetry appears to have been isolated. A series of operational changes were made with the DSN stations on Aug 10, 11, and 12 with regards to activation of the command and ranging channels, that have effectively eliminated the gaps in the telemetry.

HGA Anomaly:

The HGA gimbal is currently operational with full redundancy on side-A. The fault protection threshold for HGA stuck gimbal is at 25 seconds (50 counts).

Spacecraft Health:

All subsystems continue to report nominal status. Power reports that our excess energy has dropped from an average of 460 W-hrs per orbit to about 400 W-hrs with the initiation of the new solar array tracking scheme. The three move solar array tracking scheme will be used until August 2000, at which time autonomous tracking of the sun must resume in order to meet energy requirements as we approach aphelion.

Uplinks:

There have been 15 uplinks to the spacecraft during the last week, including new star catalog and ephemeris files, and instrument command loads. Total command files radiated to the spacecraft since launch is 3845.

Upcoming Events:

1) MM007 sequence development starts Friday Aug 13.

2) MAG calibration on Aug 31.

Last Orbit Covered by this Report = 1832
Total Orbits = 3514
Total Mapping Orbits = 1832

Recent Events:

The mm006 sequence is currently executing the daily science data collection and return sequence and will continue execution through August 25.

Preliminary status from the MOLA team is that the special off-nadir polar observation sequence executed last week was extremely successful. With half the data returned at the time of the preliminary assessment they had confirmed tracking the poles. Spacecraft health and performance during the observations were nominal.

Work has begun on the implementation and testing of the third OTM, scheduled for execution on August 11 at 17:42 UTC. The maneuver will target an approximate 49 km ground track repeat cycle, requiring about a .25 m/sec DV. Two orbits following the burn, we will implement the new TES solar array tracking scheme. With this scheme, the solar arrays are commanded to fixed positions at three different points in the orbit, thereby minimizing the amount of microphonic noise in the TES data induced by the autonomous tracking of the solar array.

Work has also begun on a MAG (Magnetometer) calibration sequence to be executed on the spacecraft August 31. This test would be composed of a series of solar array motions on the night side of the orbit and would be used to help characterize the magnetic signature of the spacecraft.

HGA Anomaly:

The HGA gimbal is currently operational with full redundancy on side-A. The fault protection threshold for HGA stuck gimbal is at 25 seconds (50 counts).

Spacecraft Health:

All subsystems continue to report nominal status.

Uplinks:

There have been 13 uplinks to the spacecraft during the last week, including new star catalog and ephemeris files, and instrument command loads. Total command files radiated to the spacecraft since launch is 3830.

Upcoming Events:

1) OTM-3 on August 11 at 17:42 UTC.

2) Implementation of new Solar Array tracking scheme two orbits after OTM-3.

3) MM007 sequence development kickoff meeting scheduled for Tue Aug 10. 4) MAG calibration on Aug 31.

Last Orbit Covered by this Report = 1746
Total Orbits = 3428
Total Mapping Orbits = 1746

Recent Events:

The mm005 sequence has finished execution and nominal mapping data collection is currently being performed by the mm006 sequence. The mm006 sequence will run through August 25.

The MOLA North/South Pole off-nadir observation sequence has finished execution as of Thursday July 29 15:00 UTC. The spacecraft is currently back in the nominal mapping configuration. A full assessment of the MOLA observations and spacecraft performance will not be available until playback of the recorded telemetry completes on Friday July 30 at 15:30 UTC.

Work is in progress on the implementation of the new TES solar array tracking scheme, where the solar arrays are commanded to fixed positions at three different points in the orbit. This change is scheduled for implementation on the spacecraft Tuesday August 10, but could be accelerated a week earlier if development and validation of the new on-board autonomously triggered command scripts continues ahead of schedule.

A formal change request has been approved by the project to perform a MAG (Magnetometer) calibration on the spacecraft. This test would be composed of a series of solar array motions on the night side of the orbit and would be used to help characterize the magnetic signature of the spacecraft. Planning for this event is now underway.

The third OTM will be performed on either August 11 or 12 (TBD). The ground track repeat cycle has drifted far enough from the desired 59.9-km walk to warrant another orbit correction maneuver. Execution of the OTM at this time will correct the walk in time for Science Campaign B, scheduled from August 20th to the 26th.

HGA Anomaly:

The HGA gimbal is currently operational with full redundancy on side-A. The fault protection threshold for HGA stuck gimbal is at 25 seconds (50 counts).

Spacecraft Health:

All subsystems continue to report nominal status.

Uplinks:

There have been 18 uplinks to the spacecraft during the last week, including new star catalog and ephemeris files, and instrument command loads. Total command files radiated to the spacecraft since launch is 3817.

Upcoming Events:

1) Implementation of new Solar Array tracking scheme on August 10.

2) OTM-3 on August 11 or 12.

Last Orbit Covered by this Report = 1661
Total Orbits = 3343
Total Mapping Orbits = 1661

Recent Events

The mm005 sequence continues execution in performing the mapping sequence data collection and return. Work has begun on the development of the next 28 -day mapping sequence, mm006, which will begin execution on July 29.

The MOLA North/South Pole off-nadir observation sequence has been successfully uplinked to the spacecraft and will begin execution July 28 at 12:23 UTC.

A formal change request has been approved by the project to stop SA auto-tracking and implement a solar tracking scheme, where the solar arrays are commanded to fixed positions at three different points in the orbit. A .24° SA rate would be utilized for the commanded "catch up" periods. This change is scheduled for implementation on the spacecraft August 10.

HGA Anomaly:

The HGA gimbal is currently operational with full redundancy on side-A. The fault protection threshold for HGA stuck gimbal is at 25 seconds (50 counts).

Spacecraft Health:

All subsystems continue to report nominal status.

Uplinks:

There have been 9 uplinks to the spacecraft during the last week, including new star catalog and ephemeris files, and instrument command loads. Total command files radiated to the spacecraft since launch is 3799.

Upcoming Events:

1) MOLA North and South Pole off-nadir observations on July 28 and 29.

2) Implementation of new Solar Array tracking scheme on August 10.

Last Orbit Covered by this Report = 1575
Total Orbits = 3257
Total Mapping Orbits = 1575

Recent Events:

The mm005 sequence continues execution in performing the mapping sequence data collection and return.

The mz0011 mini-sequence to perform the TES Solar Array tracking test successfully executed July 7. The TES team reported that the noise in their data decreased significantly when the SA stopped auto-tracking and decreased even further during the period of several minutes when the HGA was additionally commanded to stop auto-tracking. Based on the results from this test, the TES team is requesting that we stop SA auto-tracking and go to a full time implementation of the test sequence, where the solar arrays are commanded to fixed positions at three different points in the orbit. A 0.24°/sec SA rate would be utilized for the commanded "catch up" periods. The other instruments believe that they should be minimally impacted by the changes. This solar array motion strategy would work through July 2000, when power collection requirements would force us to return to SA auto-tracking. A formal change request will be submitted by the TES team Tuesday July 20.

The mz009 mini-sequence executed July 14 to perform an MR checkout in preparation for support of the DS2 microprobes in December. The MR powered on successfully, appeared to cycle through several relay modes before powering off on schedule two orbits later. A debrief is scheduled for 7/16 to verify the proper interface between the MR and MOC in transferring MR housekeeping packets. Additionally Stanford will report whether they were able to hear the UHF signal during the test.

Work continues on the MOLA North/South Pole off-nadir observation sequence scheduled to execute July 28 and 29.

HGA Anomaly:

The HGA gimbal is currently operational with full redundancy on side-A. The fault protection threshold for HGA stuck gimbal is at 25 seconds (50 counts).

Spacecraft Health:

All subsystems continue to report nominal status.

Uplinks:

There have been 9 uplinks to the spacecraft during the last week, including new star catalog and ephemeris files, and instrument command loads. Total command files radiated to the spacecraft since launch is 3790.

Upcoming Events:

1) MOLA North and South Pole off-nadir observations on July 28 and 29.

2) Kickoff meeting for mm006 sequence development on July 20. The mm005 sequence executes through July 28.

Last Orbit Covered by this Report = 1490
Total Orbits = 3172
Total Mapping Orbits = 1490

Recent Events:

The mm005 sequence continues execution in performing the mapping sequence data collection and return. The mz0011 mini-sequence to perform the TES Solar Array tracking test has been uplinked to the spacecraft and will begin execution 13:35 UTC on Friday morning. Work continues on the MOLA North/South Pole off-nadir observation sequence scheduled to execute July 28 and 29. The ranging signal was turned off on the spacecraft on July 8 for a one week period to help diagnose the cause of "tiny gaps" that have been observed in the telemetry on the ground.

HGA Anomaly:

The HGA gimbal is currently operational with full redundancy on side-A. The fault protection threshold for HGA stuck gimbal is at 25 seconds (50 counts).

Spacecraft Health:

All subsystems continue to report nominal status.

Uplinks:

There have been 16 uplinks to the spacecraft during the last week, including new star catalog and ephemeris files, and instrument command loads. Total command files radiated to the spacecraft since launch is 3781.

Upcoming Events:

1) Solar Array tracking test for TES on July 9.

2) MR checkout during week of July 12.

3) MOLA North and South Pole off-nadir observations on July 28 and 29.

Last Orbit Covered by this Report = 1318
Total Orbits = 3000
Total Mapping Orbits = 1318

Recent Events:

The mm004 sequence is still active and will control nominal mapping operations through June 30. The mm005 sequence is currently in development and will execute from July 1 through July 28.

The project approved a request by the MOLA team to perform off-nadir observations of the South Pole as the primary objective and the North Pole as a secondary objective, during the last week in July, in order to fill in coverage gaps. This was previously performed for the North Pole region during the period of Science Phasing Orbit observations during the aerobraking hiatus during the summer of 1998.

The project also approved a request to checkout the Mars Relay (MR) to verify functionality and return of MR house keeping telemetry via the MOC. The MR will be used to relay the data from the DS2 Mars microprobes. The checkout will occur the week of July 12.

HGA Anomaly:

The HGA gimbal is currently operational with full redundancy on side-A. The fault protection threshold for HGA stuck gimbal is at 25 seconds (50 counts).

Spacecraft Health:

All subsystems are reporting nominal status.

Uplinks:

There have been 12 uplinks to the spacecraft during the last week, including new star catalog and ephemeris files, and instrument command loads. Total command files radiated to the spacecraft since launch is 3749.

Upcoming Events:

1) MR checkout during week of July 12.

2) MOLA South Pole off-nadir observations during last week in July.

Last Orbit Covered by this Report = 1233
Total Orbits = 2915
Total Mapping Orbits = 1233

Recent Events:

The mm004 sequence is still active and will control nominal mapping operations through June 30.

The TES instrument has reviewed the data from the solar array autotracking pause test performed June 8 and determined that the source of the microphonic noise in their data appears to be due to the step motion of the solar arrays as they autonomously track the sun throughout the orbit. Unfortunately, after pausing auto tracking of the solar arrays for about 8 minutes, the catch-up period as the solar arrays were commanded to resume auto tracking introduced even worse noise in their data. The project will meet next week to discuss the results of the test and to determine further options to maximize the quality of the TES data.

The project disapproved a set of requested calibrations by the MAG and MOC instrument teams, due to the current demands on the flight operation teams in preparation for the critical MCO and MPL milestones this fall and winter. The instrument teams will be able to resubmit their requests upon completion of the MPL mission early next year.

HGA Anomaly:

The HGA gimbal is currently operational with full redundancy on side-A. The fault protection threshold for HGA stuck gimbal is at 25 seconds (50 counts).

Spacecraft Health:

All subsystems are reporting nominal status.

Uplinks:

There have been 14 uplinks to the spacecraft during the last week, including new star catalog and ephemeris files, and instrument command loads. Total command files radiated to the spacecraft since launch is 3737.

Upcoming Events:

1) The kickoff meeting for the development of the next mapping sequence (mm005) is Tuesday June 22.

Last Orbit Covered by this Report = 1147
Total Orbits = 2829
Total Mapping Orbits = 1147

Recent Events:

On Tuesday 6/8 starting at 13:45:00 UTC, the second test to temporarily interrupt the solar array autonomous tracking, first the -Y array and then both the -Y and +Y arrays, was successfully executed on the spacecraft in order to more fully identify the source of the microphonic noise that the TES instrument is seeing in their data. The TES team is still processing and evaluating their data and is expected to release the results on Friday 6/11.

The second orbit trim maneuver (OTM2) successfully executed on Thursday 6/10 at 11:49:39 UTC. The burn was intended to fix the ground track repeat cycle at approximately 59 km. This was unsuccessfully accomplished with OTM1 due to significant unaccounted for lateral force due to plume impingement off the HGA. The OTM2 burn attitude was biased appropriately for the expected lateral force and appears to have been successful. Pointing error was 10.5 mrad against a 25 mrad requirement. The NAV team has yet to report the actual ground track spacing achieved, but did provide a preliminary qualitative assessment that the burn was "very good".

Sequencing:

The mm004 sequence is still active and will control nominal mapping operations through June 30. The mz007 mini-sequence successfully completed execution on Tuesday in performing the SA auto-tracking pause test for TES diagnosis. The mz008 mini-sequence successfully completed execution on Thursday in performing OTM2.

HGA Anomaly:

The HGA gimbal is currently operational with full redundancy on side-A. The fault protection threshold for HGA stuck gimbal is at 25 seconds (50 counts).

Spacecraft Health:

All subsystems are reporting nominal status. No further change has been detected in the IMU gyro currents and all performance remains nominal. Power is reporting that they are now seeing HGA shadowing on the -Y Solar Array which is predicted by the thermal model. The Solar Arrays are providing significant excess power so this is not a problem. Additionally Power is reporting that the battery pressure has been trending down over the last few weeks. This is known as capacity fading and is expected and does not represent a degradation in capacity that would affect the performance of the mission.

Uplinks:

There have been 14 uplinks to the spacecraft during the last week, including the mz007 and mz008 mini-sequences, new star catalog and ephemeris files, and instrument command loads. Total command files radiated to the spacecraft since launch is 3723.

Upcoming Events:

1) The kickoff meeting for the development of the next mapping sequence is Tuesday June 22. This sequence will be interesting due to requests from the science teams to interrupt nominal mapping operations in order to perform special calibrations and possible targeted observations. Stay tuned.

Last Orbit Covered by this Report = 1062
Total Orbits = 2744
Total Mapping Orbits = 1062

Recent Events:

Sequencing:

The first science campaign has completed successfully. The mm004 sequence is now active and will control nominal mapping operations through June 30.

HGA Anomaly:

The HGA gimbal is currently operational with full redundancy on side-A. The fault protection threshold for HGA stuck gimbal is at 25 seconds (50 counts).

Spacecraft Events:

All subsystems are reporting nominal status. No further change has been detected in the IMU gyro currents and all performance remains nominal.

Uplinks:

There have been 14 uplinks to the spacecraft during the last week, including the mm004 sequence, new star catalog and ephemeris files, and instrument command loads. Total command files radiated to the spacecraft since launch is 3709.

Upcoming Events:

1) A second test to temporarily interrupt the solar array auto-tracking for TES troubleshooting will be executed on 6/8/99 at 13:45:00 UTC. 2) OTM-2 is scheduled for 6/10/99. The exact burn time will be determined early next week. The purpose of this OTM is to set the ground track spacing to the desired amount.

Last Orbit Covered by this Report = 976
Total Orbits = 2658
Total Mapping Orbits = 976

Recent Events:

Sequencing: The first science campaign is still on going under control of sequence mm003c. On 99-148 (5/28/99), the mm004 sequence will be uplinked. This new sequence will go active on 99-154 (6/3/99) when the on-board sequence expires.

HGA Anomaly:

The HGA gimbal is currently operational with full redundancy on side-A. The fault protection threshold for HGA stuck gimbal is at 25 seconds (50 counts).

Spacecraft Events:

On 99-141 (5/21/99), the currents for gyro-1 and gyro-3 suddenly dropped by approximately 20 mA. This lower, more efficient state of operation was known as "super-magnetized" on Mars Observer. The IMU PIE and Honeywell agree that no action should be taken. The performance is nominal, and the biases have not changed significantly since the current drop. IMU characteristics will be monitored closely over the next few weeks to ensure no changes in performance.

Uplinks:

There have been 15 uplinks to the spacecraft during the last week, including new star catalog and ephemeris files.

Upcoming Events:

1) OTM-2 is scheduled for 99-161 (6/10/99). The purpose of this OTM is to set the ground track spacing to the desired amount.

2) A second test to temporarily interrupt the solar array auto-tracking for TES troubleshooting will likely be executed during the first two weeks of June.

Last Orbit Covered by this Report = 902
Total Orbits = 2585
Total Mapping Orbits = 902

RECENT EVENTS:

MGS is successfully mapping midway through its four-week science campaign.

On 05/19/99, the HGA swapped to GDE side-B due to 12 consecutive position error counts. The GDE was swapped by the ground back to side-A to restore redundancy and is now operating nominally on side-A. The reason for the swap is still under investigation. The threshold was raised from 12 counts to 50 counts to decrease the likelihood additional spurious swaps. The azimuth gimbal is presently located at 51.5 degrees (approximately 10 degrees from the obstruction).

MGS has continuous station coverage through 06/03/99 and is returning science data at either 80 or 85.333 ksps during each Earth-view period.

The problems during OTM-1 are well characterized now and a plan is in place to improve the performance during OTM-2. The plan entails using integral initialization to reduce pointing errors, to bias the aimpoint to account for lateral forces due to plume impingement, and to pad the maximum timer by 20% to prevent early termination. The second orbital trim maneuver has been tentatively scheduled for 06/10/99.

The current on-board sequence is "mm003c.01" and expires on 06/03/99. The next sequence will be called "mm004" and development will begin on 05/25/99.

A new issue has cropped up that will begin to affect the stations in the near future. Earth occultation duration is now decreasing and will eventually vanish completely around 07/10/99. An HGA rewind during this time will cause an unexpected LOS at the station that would last approximately 12 minutes. This will first be evident when the Radio Science at ingress begins to be cut off early. A method to mitigate this will be discussed next week.

Last Orbit Covered by this Report = 805
Total Orbits = 2488
Total Mapping Orbits = 805

RECENT EVENTS:

Currently the spacecraft is operating from the MM002 sequence, executing the first continuous science campaign of the mapping mission. MM002 runs through Friday May 14, at which time the MM003 sequence will execute the rest of the science campaign through June 2. At this time all subsystems are executing nominally in support of the campaign. Specifically the resumption of autonomous HGA tracking continues without incident. The azimuth gimbal angle (Earth beta angle) is currently at 47°, moving further away every day from the obstruction at 41.5°.

The first orbit trim maneuver, OTM1, executed on time at 14:43:49 UTC on Friday May 7. Due to plume impingement from the HGA, OTM1 slightly underburned, achieving 3.53 m/s vs. the desired 3.6 m/s. More significantly, the plume impingement also applied a significant lateral force and torque to the spacecraft, resulting in a 4° pointing error. As a result, the burn was unsuccessful in achieving the desired 59 km ground track repeat spacing for the geodesy science campaign. AACS and the JPL Navigation team are currently analyzing the results of OTM1 in order to determine corrective actions for the next OTM. In order to allow time for the analysis, the program has decided to not attempt a second OTM to correct the orbit parameters until after the geodesy campaign has finished. OTM2 is now currently scheduled for June 10.

The Thermal Emission Spectrometer team (TES) has confirmed from the results of the SA Auto Track test performed last week, that autonomous SA tracking is introducing unacceptable noise in their data and have requested a change to remove this noise. The SCT is currently reviewing the change request and determining what possible options are available to accommodate the request.

UPCOMING EVENTS:

Geodesy Science Campaign continues through June 2.
OTM-2 June 10

SPACECRAFT COMMANDING:

There were 19 command files radiated to the S/C during this period. The total number of files radiated since launch is now 3673. These commands were sent in support of the following activities:

Star catalog and ephemeris file updates
Instrument non-interactive commands (NIPCs)
MM002B Sequence (Nominal mapping)

Last Orbit Covered by this Report = 718
Total Orbits = 2401
Total Mapping Orbits = 366

RECENT EVENTS:

On Thursday April 29, MGS resumed limited mapping of Mars, utilizing the fixed-HGA sequence strategy successfully executed for three weeks prior to the deployment of the HGA. In this mode of operations, the spacecraft points the instruments at Mars for ~18 hours a day, recording the science data on solid state recorders, then maneuvers to point the HGA boresight at the Earth for the remaining three orbits of the day, playing back the recorded science data. The MF004 sequence successfully executed for one week returning data in this manner. Except for DSN station problems the first day, 71% of the available recorded science data was transmitted to Earth during the week of fixed-HGA mapping operations.

On Tuesday May 4, a test was performed successfully on the spacecraft to pause autonomous tracking of the solar arrays for a ten-minute period, in order to determine if the solar array tracking is causing undesirable microphonic signatures in the TES data. Unfortunately, an error in the TES internal sequence prohibited the instrument from taking data. As a result, the test will have to be replanned for another opportunity.

Currently MGS has resumed nominal mapping operations with the uplink and activation of the MM002 sequence on May 6 00:00 GMT. The characterization of the gimbal obstruction after several azimuth gimbal motion tests was of a one-way obstruction, prohibiting azimuth gimbal motion for angles less than 41.5°. On DOY 126, the Earth-Mars Beta angle exceeded this limit, allowing for the resumption of autonomous gimbal tracking of the Earth. For the month of May MGS will have continuous DSN station coverage in support of the first science campaign (geodesy) of the mapping mission. During this time, high rate 80000 bps real-time MOC and TES data will be downlinked for 7 orbits a day and the previous day’s recorded 16000 bps telemetry played back over the remaining 5 orbits of the day.

The first orbit trim maneuver, OTM1, of the mapping phase is scheduled to be uplinked Thursday May 6 in the afternoon, with the burn execution at 14:43:49 UTC Friday May 7. This burn will optimize the ground track repeat spacing at 59 km and tighten up the frozen orbit, by making periapsis stationary at the South Pole.

At this time all subsystems are nominal after resumption of mapping.

UPCOMING EVENTS:
OTM-1 May 7
Geodesy Science Campaign begins May 7

SPACECRAFT COMMANDING:

There were 45 command files radiated to the S/C during this period. The total number of files radiated since launch is now 3654. These commands were sent in support of the following activities:

Instrument turn ons
PDS RAM Load
Battery VT Curve Update
Star catalog and ephemeris file updates
Instrument non-interactive commands (NIPCs)
MF004B Sequence (fixed-HGA)
MZ005A Mini-Sequence (TES SA Auto Track Pause Test)
MM002B Sequence (Nominal mapping)

HGA Anomaly Troubleshooting.
The HGA anomaly continues to be the top issue on MGS. The final two HGA gimbal troubleshooting tests were performed on the spacecraft this week. The results are summarized below.

Test 4 (4/23/99). This test commanded elevation from -90° to -153°, then to 153°, and finally back to -90° using GDE side-1. Results showed that full range of motion is still available on the HGA elevation gimbal.

Test 5 (4/24/99). This test applied powered hold to azimuth and elevation gimbals for 58 minutes on GDE side-1, and then removed powered hold from elevation. Powered hold was maintained on azimuth for 8 hours. Then, another azimuth test of ±2.5° motion was performed. The results showed that the temperatures on the azimuth gimbal were quite a bit lower than thermal predictions. Due to potential inaccuracies in the thermal modeling used for the predictions, the results do not conclusively point to an MLI blanket problem. However, the MLI blankets are certainly not exonerated. The results of the second half of the test show that azimuth was free to move in the positive direction to the desired position of 43.85°. When commanded back to 38.85°, the azimuth gimbal hit the obstruction at about 41.5° and stayed there for the remainder of the test with the expected jitter.

Conclusions From HGA Troubleshooting Tests.
1) The HGA elevation gimbal appears to be completely healthy.

2) Both GDEs and both encoders appear to be healthy.

3) The HGA azimuth gimbal appears to be free to move in the positive direction. Motion in the negative direction less than 41.5° appears to be unachievable.

4) The obstruction has moved slightly during the tests from about 41.03° to about 41.5°. However, this angle motion represents only several thousanths of an inch on the outer diameter. Thus, the obstruction is thought to be essentially stationary.

Failure Theories.
A new leading failure theory has emerged. A bolt in the gimbal assembly may have backed out by about one quarter of an inch to a height that is being struck by the rotating stop. This bolt is at an azimuth position of 41.57°. The mechanical group is still reviewing data and drawings associated with this new theory. There other two failure theories, MLI blanket interference and a cable management problem, are now thought to be less likely.

Successful Return To Fixed HGA Mapping.
On Wednesday afternoon (4/28/99), a 7-day fixed HGA mapping sequence (mf004b) was uploaded to the spacecraft which began nominal execution on Wednesday evening. The instrument turn-on began on Wednesday afternoon. When the command was uplinked to set the downlink to S&E-1, the PDS found to be in ROM EOM. The reason for this is still unknown, but an ISA has been opened. The PDS software was reloaded, and the subsequent command to S&E-1 downlink was successful. The MOC and MOLA instruments were then powered on late Wednesday afternoon.

On Thursday (4/29/99), during the Earth-pointed ISH, the fixed HGA mapping sequence was verified to be executing nominally. As part of the PDS cleanup commanding, the PDS telemetry patch was uplinked and verified. A full MRO of the PDS was performed and validated. The TES instrument was powered on, as well as the MAG/ER instrument.

Upcoming Events.
Next Tuesday (5/4/99), a mini-sequence will be uplinked to pause the solar array auto-tracking for a period of 10 minutes. The TES instrument team has observed a signature in their data which suggests the presence of undesirable microphonics. This mini-sequence should determine if the solar array tracking is the cause of the microphonics.

Next Thursday (5/6/99), the first standard mapping sequence since the HGA anomaly will go active. Standard mapping is possible at this time because the Earth beta angle is greater than 41.5°, which allows the HGA azimuth gimbal to operate in the usable region.

Next Friday (5/7/99), the first delta-v maneuver (OTM-4) since the HGA deployment will execute to set up the desired ground-track spacing for the science teams. It is expected to be between 80 and 100 seconds in duration.

Long-Term Planning.
If the conclusions from the HGA troubleshooting are correct, standard mapping will be possible until February of 2000. After that time, fixed HGA mapping at a minimum will be possible. Techniques to improve the data return after February of 2000, such as yawing the spacecraft during nadir-pointing or using the azimuth gimbal region near 180°, are still being analyzed to determine if they are feasible.

HGA Anomaly

On the night of Thursday 4/15/99 (99-109), the MGS spacecraft was found to be in contingency mode at with HGA positions of az=41.03°, el=-90.0°. The HGA c-mode targets are az=0.0°, el=-90.0°, indicating the presence of a stuck gimbal. REDMAN switch summary word showed that the HGA and Bus had both swapped to side-2. HGA was also marked as DEAD, meaning that REDMAN would take no actions in the event of further HGA faults. The audit queue was MRO’d and showed the following:

At 99-106/04:24:24, stuck HGA gimbal was detected
At 99-106/04:24:25, HGA swapped to side-2
At 99-106/04:24:37, bus swapped to side-2
At 99-106/04:24:43, HGA marked dead and contingency mode was entered
At 99-106/04:26:43, the IMU was swapped to high rate.

Other than the stuck HGA, the spacecraft is healthy and performing well.

Anomaly Recovery Commanding

In addition to dumping the audit queue, REDMAN total error counters were MRO’d. HGA position counts were incrementing as expected, and all other counts were stationary. The HGA position counts were because the c-mode azimuth target of 0° could not be achieved, creating a jittering motion on the spacecraft as the gimbal was commanding into the obstruction. The azimuth gimbal was commanded to new c-mode targets of 41.03°, but the jitter persisted. The spacecraft was commanded to sun’star’init to establish inertial reference. However, after 14 orbits Starex had still failed to converge. The team concluded that jitter was perturbing the spacecraft enough to preclude Starex convergence. A general memory load was issued to set hga’ok bit to not_okay which stopped the articulation software from executing. The jitter persisted because a GDE command was latched into the electronics. Finally, the HGA side-B was powered off via hardware command, which stopped the jitter and allowed Starex converge on first attempt. A 5-hour Earth-point ISH was commanded and SSR data was played back.

Sequencing

The first 16-hour ANS sequence was loaded Tuesday night (4/20) and went active Wednesday (4/21) morning. This sequence spends roughly 3 orbits in array normal spin with the stuck HGA boresight pointed at Earth, then spends about 1 orbit in sun'star'init with the +X axis pointing roughly at the sun, and then repeats the cycle. During ANS, the spacecraft is spinning but not processing stars, and is receiving 2K engineering data. During SSI, the spacecraft is spinning and processing stars during the eclipse, and receives no downlink data. Wednesday afternoon a new sequence was uplinked which extended this same sequencing for 10 days.

Gimbal Troubleshooting Tests

Several gimbal troubleshooting tests have been developed to gather data on the nature of the obstruction. A summary of the first five tests is shown below.

Test 1 (4/21/99). Using GDE side-2, the azimuth gimbal was commanded with rate mode to a position of 41.50°, then to 40.75°, then back to 41.03°, and then powered off. The initial power up showed that the azimuth gimbal was no longer at 41.03°, but rather at 41.30°. When the gimbal was commanded to 41.50°, there was a delay of about 3 seconds prior to motion start. The gimbal was able to achieve the 41.5° target (with a 2 encoder count overshoot). When the gimbal was commanded back to 40.75°, it moved to about 41.35° and then began jittering about that position, much like it had during the recent contingency mode entry. No further motion was observed, and the HGA was then powered off.

Test 2 (4/22/99). Using GDE side-2, the azimuth gimbal was commanded in rate mode to 42.35°, and then back to 40.35°, and then powered off. The results showed that azimuth came up at about 41.35°, moved successfully to 42.35°, and then moved back against the obstruction at about 41.40°. These results give optimism that azimuth is free to move in the positive direction.

Test 3 (4/22/99). Using GDE side-1, the elevation gimbal was commanded from -90° to -100°, then to -80°, and back to -90°. All elevation motion was nominal. However, the azimuth gimbal which had a residual command to 40.35° was able to move to 40.98°, and then when it was re-targeted as part of the elevation command, was able to achieve its target of 41.35°. These results seem to suggest that elevation gimbal looks normal, and that the obstruction is independent of GDE sides.

Test 4 (Expected 4/23/99). This test will command elevation from -90° to -153°, then to 153°, and finally back to -90° using GDE side-1. Results will show whether full range of motion is available on elevation gimbal.

Test 5 (Expected 4/24/99). This test will apply powered hold to azimuth and elevation gimbals for 58 minutes on GDE side-1, and then remove powered hold from elevation. Power hold will be maintained on azimuth for 8 hours. Then, another azimuth test of ±2.5° motion will be performed. The purpose of test 5 is to get a thermal estimate of the integrity of the MLI blanket near the azimuth gimbal, and to gather more data on azimuth gimbal motion.

Long Term Plan To Return To Mapping.

A preliminary long term plan was laid out which entailed the following milestones.
4/28 Power on the instruments
4/29 Begin execution of a fixed HGA mapping sequence for 8 days
5/6 Execute OTM-4 to set up the appropriate ground track repeat cycle
5/6 Begin execution of an articulating HGA mapping sequence

Thursday, April 8, 1999 (DOY 092/19:00:00 to DOY 098/00:00:00 UTC)

Last Orbit Covered by this Report = 366
Total Orbits = 2049
Total Mapping Orbits = 366

RECENT EVENTS:

MGS is currently running under the control of the MM001 sequence, the first deployed high gain antenna (HGA) mapping sequence. On Monday DOY 95 at 01:39 GMT, the HGA was scheduled in the sequence to "unpark" the HGA from its stowed configuration, where it is positioned when out of contact with the Earth, and to resume autonomous Earth tracking and downlink of science data. However, the DSN station was not able to lockup on the spacecraft signal. The SCT came in, and upon analysis of the situation, found an error in the on-board stored script which manages the parking and unparking of the HGA. A temporary patch was made to the on-board script to correct the problem for the short term. The root cause has subsequently been identified and the MGS ground sequence software is currently being updated.

All subsystems are currently in good health and performing nominally in the mapping configuration. AACS pointing appears to be good from the spacecraft perspective, although the instrument teams have not yet provided any feedback from their observational analyses with less than a week of mapping completed. Autonomous tracking of the solar arrays and HGA continue to work flawlessly. The AACS team is looking at options to reduce the pointing perturbations when the antenna is parked and unparked around DSN contact periods. Momentum buildup in the mapping configuration is matching well with the predicts, totaling about 3 or 4 desats per day.

Thermal reports that all temperatures are within limits. Power performance has been strong and continues to improve as the sun intensity increases. Currently the orbital energy balance with the transmitter on is 133 W-hrs. Battery eclipse depth of discharge is 32%, matching predictions for mapping.

Telecom also reports excellent performance. Currently the system is supporting the maximum science data return rates, 85 kbps for playback data and 80 kbps for real-time data. These rates are expected to be used through the end of October, when the Earth to Mars range will cause us to drop to the 42 kbps for playbacks and 40 kbps for real-time data. The uplink bit rate is currently at 125 bps, the nominal rate for mapping. C&DH performance continues to be exceptional with all components on their primary sides. All four Solid State Recorders are currently being used for recording, one pair each day, providing continuous science data collection. Each recorder pair is played back the next day over a ten hour DSN contact pass. Flight software is also reporting nominal operations in the mapping mode, with one exception. A floating point overflow condition was observed in telemetry late last week, with 4 counts over a couple of days. Since then there have been no additional counts. FSW is currently investigating the situation.

UPCOMING EVENTS:

Geodesy Science Campaign begins May 1.

SPACECRAFT COMMANDING:

There were 25 command files radiated to the S/C during this period. The total number of files radiated since launch is now 3511. These commands were sent in support of the following activities:

HGA unpark anomaly resolution
Star catalog and ephemeris file updates
Instrument non-interactive commands (NIPCs)

Last Orbit Covered by this Report = 303
Total Orbits = 1986
Total Mapping Orbits = 303

RECENT EVENTS:

MGS successfully deployed the HGA antenna Sunday night (March 29). Spacecraft performance was completely nominal throughout the entire event. A "coarse" HGA pointing calibration was executed three orbits after deployment of the boom and a "fine" calibration was performed Monday night. The HGA pointing biases were successfully updated following the calibrations.

On Wednesday morning the spacecraft was commanded to nadir pointing for a two orbit mapping checkout, which validated both HGA and Solar Array autonomous tracking modes. The Mars Horizon Sensor (MHSA) was on and operating during these orbits but was not controlling the spacecraft pointing.

On Thursday morning the spacecraft was again commanded back to nadir pointing for the last time (nominally) with the IMU commanded to its low rate (higher precision pointing mode). Finally the MHSA biases were updated and the spacecraft commanded to Search mode for the first time with the MHSA in closed loop control of the spacecraft.

Final preparations for the start of mapping were made on Friday morning with the instruments powered back on and the final sequence loads uplinked to the spacecraft. The first mapping sequence MM001 begins execution on DOY 093 at 00:00:00 GMT.

At this time all subsystems are reporting excellent health and the spacecraft and team are ready for the start of the primary mapping mission.

UPCOMING EVENTS:
Geodesy Science Campaign begins May 1.

SPACECRAFT COMMANDING:

There were 72 command files radiated to the S/C during this period. The total number of files radiated since launch is now 3486. These commands were sent in support of the following activities:

Instrument Turn offs
HGA Deployment and Mapping Transition Sequences (P1923, P1943, p1958)
HGA Deployment support sequences and real-time commands
Mapping Transition Real-time Commands
Star catalog and ephemeris file updates
Mission Phase bits set to Mapping
Instrument Turn ons
Instrument non-interactive commands (NIPCs)

Last Orbit Covered by this Report = 195
Total Orbits = 1878
Total Mapping Orbits = 195

Latest Orbital Elements from JPL Navigation team for orbit 158 (3/22/99):
Periapsis Altitude = 369.4 km
Orbit Period = 1 hr 57 mins 00 secs
Apoapsis Altitude = 436.8 km
Inclination = 92.9 deg
Arg of Periapsis = 263.2 deg
Local Mean Solar Time (LMST) at Descending Node = 2:03 AM

RECENT EVENTS:

MGS continues its excellent performance in the execution of the "fixed-HGA" sequences, returning approximately 18 hours of high rate 16 kbps science telemetry during a daily three orbit Earth pointed contact period. Currently the third and final fixed-HGA sequence, MF003 is controlling the spacecraft events. All subsystems continue to report excellent health and there are no current issues with respect to the current mode of operations.

The spacecraft team is currently focused on final preparations for the deployment of the HGA on March 29, consisting of sequence reviews and validation in the Spacecraft Test Laboratory (STL) and the finalization of contingency plans.

UPCOMING EVENTS:

Fixed HGA Mapping continues through March 28
HGA Deployment on March 29

SPACECRAFT COMMANDING:

There were 14 command files radiated to the S/C during this period. The total number of files radiated since launch is now 3414. These commands were sent in support of the following activities:

Fixed HGA Mapping Sequence 3 (MF003)
Nominal star catalog and ephemeris file updates
Instrument non-interactive commands (NIPCs)

Last Orbit Covered by this Report = 110
Total Orbits = 1793
Total Mapping Orbits = 110

Latest Orbital Elements from JPL Navigation team for orbit 85 (3/15/99):
Periapsis Altitude = 369.4 km
Orbit Period = 1 hr 57 mins 00 secs
Apoapsis Altitude = 436.8 km
Inclination = 92.9 deg
Arg of Periapsis = 263.2 deg
Local Mean Solar Time (LMST) at Descending Node = 2:03 AM

RECENT EVENTS:

MGS continues its excellent performance in the execution of the "fixed-HGA" sequences, returning approximately 18 hours of high rate 16 kbps science telemetry during a daily three orbit Earth pointed contact period. Currently the second fixed-HGA sequence, MF002 is controlling the spacecraft events. All subsystems continue to report excellent health and there are no current issues with respect to the current mode of operations.

The spacecraft team is currently focused on final preparations for the deployment of the HGA on March 29, consisting of sequence reviews and validation in the Spacecraft Test Laboratory (STL) and the finalization of contingency plans.

UPCOMING EVENTS:

Fixed HGA Mapping continues thru March 28
HGA Deployment on March 29

SPACECRAFT COMMANDING:

There were 12 command files radiated to the S/C during this period. The total number of files radiated since launch is now 3400. These commands were sent in support of the following activities:

Fixed HGA Mapping Sequence 2 (MF002)
Nominal star catalog and ephemeris file updates
Instrument non-interactive commands (NIPCs)

Last Orbit Covered by this Report = 1707
Total Orbits = 1707
Total Mapping Orbits = 24

Latest Orbital Elements from JPL Navigation team for orbit 1633 (3/4/99):
Periapsis Altitude = 369.4 km
Orbit Period = 1 hr 57 mins 00 secs
Apoapsis Altitude = 436.8 km
Inclination = 92.9 deg
Arg of Periapsis = 263.2 deg
Local Mean Solar Time (LMST) at Descending Node = 2:03 AM

RECENT EVENTS:

The Mars Orbiter Camera (MOC) calibration week has been successfully completed. The three week period of "fixed-HGA" mapping, before deployment of the HGA, officially began on 3/9. Currently the MF001 sequence is controlling the spacecraft activities for the first week of mapping. The past week was spent in generation of the next fixed-HGA sequence and the HGA deployment and calibration sequences.

All subsystems continue to report excellent health and performance. Attitude control during the MOC focus week and during the initial few days of fixed-HGA mapping has been excellent. The only issue of note from AACS was an update to increase the solar array rewind rate to ensure the array is fully rewound upon initiating auto tracking at solar eclipse egress. This was done to eliminate excessive attitude rates upon initiation of auto tracking as the panels tried to catch up to their expected initial positions. Since the update, performance has been nominal. The thermal subsystem remains nominal as all S/C temperatures continue within limitations. The power subsystem continues strong performance maintaining a current energy balance of 160 W-hrs, with all of the instruments powered on and solar array auto tracking enabled. Solar eclipse DoD is 32% after the 38 minute eclipse period of the orbit. The 2A solid state recorder, which had unexpectedly powered off several weeks earlier, has been working normally in supporting the science data return during the MOC focus checks and initial mapping sequences. Telecom performance has been superb, supporting our maximum downlink rate of 85 kbps for the science data playbacks.

All science playbacks during the fixed-HGA sequence have been initiated autonomously by the spacecraft using on-board sequences triggered by solar eclipse entry detection. The initial assessment after the first few days of mapping have shown Autonomous Eclipse Detection (AEM) has been working very well, with actual eclipse times within 10 seconds of the Navigation predicted times. The use of AEM will allow for longer duration sequences of significantly smaller uplink sizes during mapping, minimizing the amount of operations work required to support mapping sequence development.

UPCOMING EVENTS:

Fixed HGA Mapping continues thru March 28
HGA Deployment on March 29

SPACECRAFT COMMANDING:

There were 22 command files radiated to the S/C during this period. The total number of files radiated since launch is now 3388. These commands were sent in support of the following activities:

Fixed HGA Mapping Sequence 1 (MF001)
Command loss timer resets
Nominal star catalog and ephemeris file updates
Battery VT curves to VT4S
SA rewind rate update

Last Orbit Covered by this Report = 1594
Total Gravity Calibration orbits accomplished = 298

Latest Orbital Elements Orbit 1543 (2/25/99):
Periapsis Altitude = 368.8 km
Periapsis Latitude = 86.1 deg South
Orbit Period = 1 hr 57 mins 00 secs
Apoapsis Altitude = 438.3 km
Inclination = 92.89 deg
Arg of Periapsis = 267.4 deg
Local Mean Solar Time (LMST) at Descending Node = 2:03 AM

RECENT EVENTS:

The Gravity Calibration period has been successfully completed. The remaining instruments, MOC, TES and MOLA were successfully powered on Sunday in preparations for a week of mapping nadir operations for the MOC focus/calibration events scheduled for the week of 3/1. The MAG and ER instruments have been on since the start of gravity calibration operations. Currently, sequence P1582 is executing commands to support this one week MOC focus/calibration period. The past week was spent in generation and execution of a mapping nadir checkout sequence and the MOC calibration sequence, as well as planning and implementing the instrument turn ons.

On Wednesday Feb. 24, a planned nadir checkout sequence was executed on the spacecraft. For the first time, the spacecraft was commanded to nadir point with star processing enabled in the mapping attitude along with having the solar arrays autonomously track the sun. Since the HGA is still stowed, no real-time data was available during this period. All data during the two orbits of commanded nadir operations were recorded and subsequently played back over a single Earth pointed orbit. After playing back the nadir telemetry, it was noticed that the X and Z reaction wheels were being commanded at a greater frequency and drawing more current than expected. The activity was attributed to the .17 Hz frequency from the damaged -Y Solar Array coupling into the AACS control law. To prevent any possible damage to the wheels the nadir checkout sequence was canceled by real-time command and replaced with a nominal gravity calibration sequence. Subsequently, AACS implemented a 0.17 Hz notch filter to account for the solar array, which was validated with a second nadir checkout sequence on Friday. AACS performance during the second nadir checkout sequence was exceptional.

Upon return from the nadir checkout orbit after solar eclipse exit, however, the batteries continued to discharge instead of recharging as expected. Inspection of the sequence revealed that slower solar array rates used during normal gravity calibration operations were being implemented earlier than required and, coupled with a large slew from the nadir attitude to the earth pointed attitude, resulted in a longer sun outage than desired. The depth of discharge of the batteries upon entry into the next solar eclipse were 23.7% and 25.4%, respectively, instead of being fully charged as normal. Upon exiting solar eclipse, the batteries had further discharged down to 51.8% and 54.1% SOC, respectively. Contingency mode entry due to low state of charge occurs when the state of charge of both batteries is below 48%. Within three orbits of normal gravity cal operations, the batteries were back to full charge again.

Currently all subsystems report excellent health and performance. Attitude control has been outstanding, with flawless star processing performance during the last orbits of gravity cal. During the nadir checkout orbits, star processing in the mapping attitude also worked very well. Additionally solar array autonomous tracking worked as expected during the nadir checkout orbits. All changes made to the FSW to accommodate the 2AM (vs original 2PM) fixed local solar time orbit were implemented and worked as expected during the nadir checkout sequence. The S/C temperatures continue within limitations. The power subsystem continues strong performance maintaining a current energy balance of 140 W-hrs, with all of the instruments powered on and solar array auto tracking enabled. Solar eclipse DoD is 30% with the instruments on. The 2A solid state recorder underwent a full functional checkout on Monday Feb. 22 and Tuesday Feb. 23, after the power anomaly the previous week. SSR 2A was recorded on for almost 14 hours at the maximum 16 kbps record rate and all data was played back normally. Final resolution of the recorder anomaly is scheduled for Wed March 3. In preparation for the deployment of the HGA at the end of March, an in flight test was performed to validate the ability to switch to the backup LGA transmitter. This was performed successfully on Tuesday Feb. 23. At this time all S/C systems are ready for the upcoming MOC Calibration and Fixed HGA mapping periods.

UPCOMING EVENTS:

MOC Calibrations from March 1 to 8
Fixed HGA (Contingency Science) March 9 to March 28
HGA Deployment on March 29,1999

SPACECRAFT COMMANDING:

There were 48 command files radiated to the S/C during this period. The total files radiated since launch is now 3366. These commands were sent in support of the following activities:

Nadir Checkout sequence 1 (P1532)
Gravity Calibration sequence (P1540)
Nadir Checkout sequence 2 (P1554)
MOC Calibration sequence (P1582)
FSW Mapping 2AM Patch
SSR 2A anomaly commands
Battery VT curves to VT4S
Telecom RF Switch 2 Test for HGA deployment
Command loss timer resets
Nominal star catalog and ephemeris file updates
Unload Buffer MRO
Instrument Turn On and NIPCs

Last Orbit Covered by this Report = 1484
Total Gravity Calibration orbits accomplished = 200

Transfer to Mapping Orbit completed successfully on Orbit 1473 (2/19/99)
DV = 22.0 m/sec, Burn Duration = 26.0 sec

Pre-TMO Orbital Elements Orbit 1473 (2/19/99):
Periapsis Altitude = 414.0 km
Periapsis Latitude = 70.8 deg South
Orbit Period = 1 hr 58 mins 30 secs
Apoapsis Altitude = 419.5 km
Inclination = 92.948 km
Arg of Per = 214.9 deg
Local Mean Solar Time (LMST) at Descending Node = 2:03 AM

Post-Burn Orbital Elements Orbit 1474 (2/19/99):

Periapsis Altitude = 367.8 km
Periapsis Latitude = 86.8 deg South
Orbit Period = 1 hr 57 mins 00 secs
Apoapsis Altitude = 438.5 km
Inclination = 92.910 deg
Arg of Periapsis = 268.8 deg
Local Mean Solar Time (LMST) at Descending Node = 2:03 AM

RECENT EVENTS:

Sequence P1474 is currently controlling the gravity calibration activities. TMO executed perfectly on orbit 1473 to achieve the preliminary "lock" on the MGS "frozen" mapping orbit. The orbit is nearly sun-synchronous -- a slight drift in the Local Mean Solar Time (LMST) remains (~1 minute in 42 days). Additional orbit trim maneuvers (OTM's) will be performed as necessary to correct the small dispersions remaining in the achieved orbital elements. However, OTM-1 scheduled for 2/26 has been canceled due to the excellent accuracy of the TMO burn. Further use of the main engine in the mission is not anticipated. The MGS spacecraft has its fully budgeted monopropellant fuel allocations for its frozen orbit trim maneuver, mapping, planetary quarantine, and relay mission phases. In addition, the spacecraft has an unallocated monopropellant fuel reserve of nearly 46 m/s. Approximately 5 kg of oxidizer (NTO) will go unused.

All subsystems report excellent health and performance during gravity call operations. Attitude control has been outstanding, with perfect star processing performance. The S/C temperatures continue within limitations. The power subsystem continues strong performance maintaining a current energy balance of 80 W-hrs. This represents about 10% margin of the power subsystem capacity. Autonomous eclipse management (AEM) used to initiate the eclipse ingress and egress events has been working flawlessly. The timing difference between the Navigation predictions and the spacecraft day/night detections have been on the order of 10 seconds for ingress and 40 seconds for egress. The DSN stations have had no trouble locking telemetry with these timing errors. Further correlation is on-going. The telecommunications subsystem continues solid performance. After fixing the on-board eclipse egress script for an 85 kbps playback problem, all playbacks have been proceeding smoothly.

On Tuesday 2/16, telemetry unexpectedly showed Solid State Recorder (SSR) 2A powered on but drawing no current. As a point of note, SSR2A had been commanded along with SSRs 1B and 2B to low power mode for the final week of aerobraking, the first time in the mission this mode has been utilized. Commands were immediately prepared and uplinked to power cycle SSR2A, which resulted in a successful power up. Currently SSR2A appears to be functioning properly. SEAKR, the SSR manufacturer, has been notified of the situation and is looking into the matter. In the meantime, command products are in preparation to perform a functional checkout of the recorder.

UPCOMING EVENTS:

Nadir Pointing Checkout on February 24
Instrument Power On February 27
MOC Calibrations from March 1 to 8
Fixed HGA (Contingency Science) March 9 to March 28
HGA Deployment on March 29,1999

SPACECRAFT COMMANDING:

There were 50 command files radiated to the S/C during this period. The total files radiated since launch is now 3318. These commands were sent in support of the following activities:

Nominal Gravity Calibration sequences (P1370, P1455, P1474)
TMO Maneuver (A1473)
TMO AEM script fix for 85 k Playbacks
New Alternate Mission Mode EDF and SCP telemetry maps
Battery VT curves to VT3S
ABX Telemetry Playbacks
Full SCP MROs
Command loss timer resets
Nominal star catalog and ephemeris file updates
Unload Buffer MRO
SSR 2A anomaly commands

Last Orbit Covered by this Report = 1302

Total Phase I Aerobraking orbits accomplished = 180

Total Phase II Aerobraking orbits accomplished = 709

Total Science Phasing orbits accomplished = 290

Total Gravity Calibration orbits accomplished = 18

Apoapsis altitude = 451.1 km
Apoapsis altitude decrease since start of aerobraking = 53574.7 km

Periapsis altitude = 381.5 km

Current Orbit Period = 01:58:50
Orbit Period decrease since start of aerobraking = 43:00:43

Starting Phase II orbit period = 11:38:02

RECENT EVENTS:

The Mars Global Surveyor spacecraft has successfully completed the aerobraking mission. The 61.9 m/s main engine maneuver executed precisely as planned at 08:02 (01:02 MST) Thursday morning 2/4/99. The current orbit is nearly circular and has met the requirements for this phase of the mission. S/C activities have now transitioned to the Gravity Calibration phase. During this period the S/C will remain Earth-pointed continuously. The S/C radio signal will be monitored by ground experimenters and navigators to gather information on the Mars gravity field. Atmospheric radio science will also be obtained by monitoring the radio signal as the S/C travels behind Mars and again when it emerges back into Earth’s view.

On Tuesday at 18:20 MST a water main broke in the SSB building where the MSA is located. The resulting flood damaged communication hardware causing a catastrophic outage of voice, data and telephone service. During this critical latter part of aerobraking, without ground control the spacecraft had only 48 hours of remaining life. The P1271 sequence was radiated from the backup ACE station at JPL. Two team members were immediately transferred to JPL to help assure S/C control was maintained during the outage. Repair personnel were immediately brought on site. The capability to generate aerobraking sequences was demonstrated at JPL and would have been used if the voice and data capability had not been restored about 9 hours later. The P1278 sequence was built and radiated from the Denver MSA.

Prior to the final aerobraking maneuver, two Automated Eclipse Management (AEM) scripts were loaded into S/C memory. These scripts, when enabled, execute when the S/C enters solar eclipse (ingress) or exits solar eclipse (egress). Following the ABX maneuver, the first gravity calibration sequence was successfully loaded and executed. This action enabled the AEM scripts and the gravity calibration effort was underway. A new Contingency Mode script that matches the new environment was loaded as well as commands to power the MAG/ER instrument on.

Sequence P1287 is currently controlling the gravity calibration activities. A replacement sequence, P1311 has been prepared and loaded. It will take control on Saturday.

All subsystems report excellent health and performance. Attitude control maintained outstanding performance during the waning orbits of aerobraking, even though insufficient time was available to fully converge star processing during the short orbits. A bad attitude update occurred on orbit 1285 which caused loss of downlink until the latter part of orbit 1286 when STAREX recovered without aid. The power subsystem continues strong performance. The final orbits of aerobraking reduced the excess energy to a minimum of 45 W-hours per orbit. This represents about 5% margin of the power subsystem capacity. No additional contingency files were required to maintain the margin. The S/C temperatures continue within limitations. A fault protection threshold was modified slightly to prevent an inadvertent heater switch near a propulsion valve cluster. The telecommunications subsystem continues solid performance. Troubles locking on the 85 Kbps playback each orbit has been attributed to an incorrect command parameter in the egress sequence. A correction has been identified and prepared for loading later today. An ISA will be initiated to document the error.

The maneuver to place the panels directly on the Sun while warming the MOLA instrument is still required. When the S/C transitioned from this inertial hold state to ANS (array normal spin) the panel movement caused the S/C to drift off Earth-point momentarily. This occurred during aerobraking as well and forces loss of both uplink and downlink momentarily. A command to reduce the panel motion rate was approved and loaded that has prevented the loss of downlink. The maximum panel rate was reduced by about one sixth.

Current predictions put the first Transition to Mapping Orbit (TMO) burn on February 19. The final maneuver to the frozen mapping orbit will occur about 1 week later. Five days of MOC (Mars Orbiter Camera) calibration maneuvers will follow, then the fixed HGA (High Gain Antenna) mission will begin.

UPCOMING EVENTS:

MSOP Readiness Review February 16, 1999
First OTM to final orbit (TMO) ~ February 19, 1999
Final OTM to mapping orbit ~ March 1, 1999
HGA Deploy ~ March 30,1999

SPACECRAFT COMMANDING:

There were 25 command files radiated to the S/C during this period. The total files radiated since launch is now 3268. These commands were sent in support of the following activities:

Nominal drag pass sequences (P1258, P1265, P1271, P1278, P1281)

Nominal corridor control maneuver sequences (A1256, A1269, A1284-ABX)

Nominal Gravity Calibration sequences (P1287, P1311)

Command loss timer resets

Nominal star catalog and ephemeris file updates

Change to 250 bps D/L to aid in STAREX recovery

AEM ingress and egress scripts

Updated Contingency Mode script

MAG/ER instrument on

Modify solar array gimbal maximum rate = 1/6

Modify the RCS-1 DTC fault protection limit

Last Orbit Covered by this Report = 1252

Total Phase I Aerobraking orbits accomplished = 180

Total Phase II Aerobraking orbits accomplished = 677

Total Science Phasing orbits accomplished = 290

Apoapsis altitude = 599.2 km
Apoapsis altitude decrease since start of aerobraking = 53426.7 km

Periapsis altitude = 109.2 km

Current Orbit Period = 01:55:21
Orbit Period decrease since start of aerobraking = 43:04:12

Starting Phase II orbit period = 11:38:02

RECENT EVENTS:

The Mars Global Surveyor spacecraft maintains excellent health and performance during the final days of aerobraking. The aerobraking walk-out phase continues per plan. Peak dynamic pressures have been greatly reduced due to the periapsis raise maneuvers completed as part of the walkout. About 4.5 minutes were removed from the orbit period over the past 25 drag passes. The apoapsis altitude has been dropping at the rate of 7.6 km per drag pass which is about half the rate reported last period. The final main engine maneuver, ABX, is now planned for about orbit 1275 which will occur on Wednesday morning and will raise the S/C periapsis clear of the Martian atmosphere. Lower dynamic pressures and smaller apoapsis altitude reductions are expected as the walk-out continues. Periapsis raise maneuvers were ordered for orbit 1238 and 1256. The magnitude of these maneuvers has been tuned to provide the correct apoapsis altitude for the ABX on orbit 1275.

Currently, sequence P1252 is controlling S/C activities. It will be replaced by P1258 late this evening. P1258 will control activities starting with orbit 1258 through orbit 1264. No emergency sequences have been required due to periapsis timing errors. All sequences have contained 7 primary orbits and 6 backup orbits. Multiple uplink opportunities are still available to assure sequence loading.

Subsystems continue to report excellent S/C health and performance. The -Y solar array yoke has shown no change in structural performance. Attitude knowledge has been maintained throughout the period with excellent star processing. On the first orbit of a new sequence, the star processing routine is enabled later than usual and may not complete convergence prior to entering the next drag pass. Contingency commands have been prepared to react to possible star processing problems because of the shortened orbit period. The power subsystem reports strong performance with battery discharge depths gradually rising due to increasing eclipse period, now reaching 30.5% each drag pass. There are about 70 W-hours of excess energy generated each orbit. Several contingency files have been prepared to provide more energy by powering down components that are not needed for aerobraking, but still keeping the units healthy. Three unused Solid State Recorders (SSRs) were commanded to standby to conserve power. The S/C temperatures are being maintained above limitations despite heater management for power considerations and increasing eclipse periods. The current eclipse duration is 38.5 minutes, heading to a maximum of 40 minutes. The telecommunications subsystem continues solid performance.

The final ABX maneuver design was delivered to the S/C team last night. A final version of the sequence was built and is in review. The sequence will be tested in the STL this evening. The sequence product to be loaded for Wednesday’s main engine maneuver will be updated with the latest Navigation timing and reviewed prior to uplink. The first Transition to Mapping Orbit (TMO) sequence was tested again this period and the results are in review.

Once the ABX maneuver completes, the continuing drag sequence will assure the S/C is safe in case the maneuver is aborted. The TMO sequence will be loaded as soon as possible after the successful ABX can be verified. The TMO sequence will provide gravity calibration data with MAG/ER science as well. During this period, the S/C will remain Earth-pointed in either ANS (Array Normal Spin) mode or in an inertially fixed attitude, still Earth-pointed but with the panel positions optimized for maximum power generation.

UPCOMING EVENTS:

Periapsis for Orbit 1253 DOY032/20:22:55 Through
Periapsis for Orbit 1275 DOY034/14:10:23 UTC
The ABX maneuver to end Aerobraking - DOY034/15:06:14

(Note: MST = UTC-7 hours DOY032=2/1)

SPACECRAFT COMMANDING:

There were 9 command files radiated to the S/C during this period. The total files radiated since launch is now 3243. These commands were sent in support of the following activities:

Nominal drag pass sequences (P1234, P1240, P1246, P1252)

Nominal corridor control maneuver sequences (A1238)

Command loss timer resets

Command the SSRs to standby to conserve power

Last Orbit Covered by this Report = 1193

Total Phase I Aerobraking orbits accomplished = 180

Total Phase II Aerobraking orbits accomplished = 618

Total Science Phasing orbits accomplished = 290

Apoapsis altitude = 1237.2 km
Apoapsis altitude decrease since start of aerobraking = 52788.7 km

Periapsis altitude = 102.3 km

Current Orbit Period = 02:10:12
Orbit Period decrease since start of aerobraking = 42:49:21

Starting Phase II orbit period = 11:38:02

RECENT EVENTS:

The Mars Global Surveyor spacecraft continues excellent aerobraking performance. Nearly 8 minutes have been removed from the orbit period over the past 22 drag passes. The apoapsis altitude has been dropping at the rate of 14.75 km per drag pass which is near the new plan of 14.4. The dynamic pressure 10-orbit running mean is now 0.222 N/m2 but is no longer used to determine aerobraking progress or for maneuver decisions. No corridor control maneuvers have been required to maintain the apoapsis altitude decay rate. Projections now show orbit 1208 will mark the beginning of the walkout phase when a periapsis raise maneuver of about 1.0 m/s will be executed daily for five days. The final maneuver, ABX will be a main engine maneuver and will raise the S/C periapsis clear of the Martian atmosphere. Orbit 1208 is predicted to occur on January 28 at about 20:00 MST. The schedule shows ABX will occur on February 3.

The spacecraft team is now preparing 2 drag sequences daily from 2 daily navigation solutions. This was required to maintain periapsis timing margins for S/C safety. Currently, sequence P1194 is controlling the S/C activities. It will be replaced this evening with P1199 which will control activities starting with orbit 1199 through orbit 1206. No emergency sequences have been required due to periapsis timing errors. All sequences have contained 7 primary orbits and 5 backup orbits. Starting with sequence P1199, all sequences will contain 7 primary and 6 backups for extra margin against possible station outages.
Multiple uplink opportunities are still available to assure sequence loading. Also starting with P1199, no science playback will occur each orbit due to timing restrictions.

Subsystems continue to report excellent S/C health and performance. The -Y solar array yoke has shown no change in structural performance. Peak dynamic pressures have been maintained below 0.28 N/m2, well below the allowable 0.40 N/m2. Attitude knowledge has been maintained throughout the period with excellent star processing. The power subsystem reports strong performance with battery discharge depths now reaching 29.5% each drag pass. The total DoD has dropped slightly due to the decreased S/C load during the eclipse. The minimum MOLA laser temperature observed this period was 12.5°C using the 35 minute warming maneuver. A slight upward trend is still observed due to the decreasing orbit period. The telecommunications subsystem continues solid performance.

UPCOMING EVENTS:

Periapsis for Orbit 1194 DOY027/21:03:08 Through
Periapsis for Orbit 1215 DOY029/17:05:11 UTC

(Note: MST = UTC-7 hours DOY025=1/25)

SPACECRAFT COMMANDING:

There were 12 command files radiated to the S/C during this period. The total files radiated since launch is now 3206. These commands were sent in support of the following activities:

Nominal drag pass sequences (P1177, P1183, P1188, P1194)

Nominal corridor control maneuver sequences (None)

Command loss timer resets

Nominal star catalog and ephemeris file updates

Change the command loss timer to 18 hours

Last Orbit Covered by this Report = 1171

Total Phase I Aerobraking orbits accomplished = 180

Total Phase II Aerobraking orbits accomplished = 596

Total Science Phasing orbits accomplished = 290

Apoapsis altitude = 1561.7 km
Apoapsis altitude decrease since start of aerobraking = 52464.1 km

Periapsis altitude = 103.6 km

Current Orbit Period = 02:18:09
Orbit Period decrease since start of aerobraking = 42:41:24

Starting Phase II orbit period = 11:38:02

RECENT EVENTS:

The Mars Global Surveyor spacecraft continues excellent aerobraking performance. More than 10 minutes have been removed from the orbit period over the past 30 drag passes. The apoapsis altitude has been dropping at the rate of 13.6 km per drag pass which remains close to the plan of 13.1 km. The dynamic pressure 9-orbit running mean is now 0.192 N/m2 but is no longer used to determine aerobraking progress or for maneuver decisions. Only the peak dynamic pressure is monitored to assure S/C solar array panel health. No corridor control maneuvers have been required to maintain the apoapsis altitude decay rate. The latitude of periapsis is now about 82° South and will pass the South Pole within the next few days. Projections show orbit 1230 will mark the beginning of the walkout phase when a periapsis raise maneuver of about 1 m/s will be executed daily for four days. The final maneuver, ABX will be a main engine maneuver and will raise the S/C periapsis clear of the Martian atmosphere. Orbit 1230 is predicted to occur on January 30 at about 15:30 MST. The schedule shows ABX will occur on February 4.

The spacecraft team is now preparing 2 drag sequences daily from 2 daily navigation solutions. This was required to maintain periapsis timing margins for S/C safety. Currently, sequence P1172 is controlling the S/C activities. It will be replaced this evening with P1177 which will control activities starting with orbit 1177 through orbit 1182. Because of compounding periapsis timing errors, 2 emergency sequences were required this period. Emergency sequence P1152 was required due to diverging periapsis times for the last 3 orbits of the P1145 sequence. P1155 was built and loaded per schedule 3 orbits later. On Sunday, a similar situation required the emergency sequence P1162 to cover the last 3 orbits of P1155. Starting this morning (Monday) two sequences are being built daily to assure accumulated timing errors to not exceed the allowable margins. Starting today all sequences contain 7 primary orbits and 5 backup orbits. Only 5 or 6 of the primary orbits will be used to maintain near prime shift builds twice per day. Multiple uplink opportunities are still available to assure sequence loading. The uplink rate was doubled to 250 bps to maintain this uplink window margin.

Subsystems continue to report excellent S/C health and performance. The -Y solar array yoke has shown no change in structural performance. Peak dynamic pressures have been maintained below 0.25 N/m2, well below the allowable 0.40 N/m2. Attitude knowledge has been maintained throughout the period with excellent star processing. The power subsystem reports strong performance with battery discharge depths now reaching 29.5% each drag pass. The total DoD has dropped slightly due to the decreased S/C load during the eclipse. The minimum MOLA laser temperature observed this period was 12.5°C using the 35 minute warming maneuver. A slight upward trend is still observed due to the decreasing orbit period. The telecommunications subsystem continues solid performance. The increased uplink bit rate coupled with avoiding the power maneuver to ANS transition has resolved the uplink issues reported last period.

UPCOMING EVENTS:

Periapsis for Orbit 1172 DOY025/19:54:32 Through
Periapsis for Orbit 1193 DOY027/18:46:29 UTC

(Note: MST = UTC-7 hours DOY025=1/25)

SPACECRAFT COMMANDING:

There were 18 command files radiated to the S/C during this period. The total files radiated since launch is now 3206. These commands were sent in support of the following activities:

Nominal drag pass sequences (P1145, P1152, P1155, P1162, P1165, P1172)

Nominal corridor control maneuver sequences (None)

Command loss timer resets

Uplink rate to 250 bps test and transition

Contingency mode script for eclipse

Battery VT level set to 5

Last Orbit Covered by this Report = 1141

Total Phase I Aerobraking orbits accomplished = 180

Total Phase II Aerobraking orbits accomplished = 566

Total Science Phasing orbits accomplished = 290

Apoapsis altitude = 1969.3 km
Apoapsis altitude decrease since start of aerobraking = 52056.6 km

Periapsis altitude = 104.9 km

Current Orbit Period = 02:28:22
Orbit Period decrease since start of aerobraking = 42:31:11

Starting Phase II orbit period = 11:38:02

RECENT EVENTS:

The Mars Global Surveyor spacecraft continues excellent aerobraking performance. About 6.5 minutes have been removed from the orbit period in the past 19 drag passes. The apoapsis altitude has been dropping at the rate of 13.3 km per drag pass which is very close to the plan of 13.1 km. The dynamic pressure 9-orbit running mean is now 0.197 N/m2, slightly higher than the 0.136 N/m2 expected to maintain the apoapsis altitude reduction plan. No corridor control maneuvers have been required. As the location of periapsis continues southward, the density variability is expected be become less dynamic since the longitudinal dependency will be gone.

Currently, sequence P1136 is controlling the S/C activities. It will be replaced later this afternoon with P1145 which will control activities starting with orbit 1145 through orbit 1154. Two backup orbits were executed this period when an uplink error caused the sequence P1134 start to be rejected. Backup orbits were executed while the P1136 sequence was prepared and loaded. Another backup orbit will be intentionally used on the 1144 pass to provide more uplink margin. By incorporating this delay, all future sequences built this week will have multiple uplink opportunities. The P1145 sequence contains 10 primary and 5 backup orbits to maintain a prime shift build, once per day. All periapsis timing predictions have been very good therefore no special, non-scheduled sequences were required.

Change requests were reviewed today to improve margins related to aerobraking operations. CCR-269 was approved to increase the uplink bit rate to 250 bps. A test will be performed to verify successful 250 bps rate operations on the S/C before permanently changing to that rate. This will provide multiple opportunities to radiate vital aerobraking sequences. Another change, CCR-270, was approved as contingency to increase the Array Normal Spin (ANS) rate to help assure inertial reference can be maintained through the short periods for star processing that remain. The command loss timer threshold will be set to 18 hours next week when two sequence builds per day begin. This will help S/C recovery in case an unexpected H/W failure occurs in the S/C uplink path.

Subsystems continue to report excellent S/C health and performance. The -Y solar array yoke has shown no change in structural performance. Attitude knowledge has been maintained throughout the period with excellent star processing. The power subsystem reports strong performance with battery discharge depths now reaching 30% each drag pass. The total DoD has dropped slightly due to the decreased S/C load during the eclipse. The load has decreased because the S/C is not cooling as much thanks the shorter orbits. The minimum MOLA laser temperature observed this period was 11.3°C using the 35 minute warming maneuver. A slight upward trend is still observed due to the decreasing orbit period. The telecommunications subsystem continues solid performance. Uplink errors have been attributed to S/C motion off Earth-point during the long sequence uploads. Steps are being taken to avoid the motion event each orbit to increase uplink success.

UPCOMING EVENTS:

Periapsis for Orbit 1142 DOY022/20:21:00 Through
Periapsis for Orbit 1171 DOY025/17:08:40 UTC

(Note: MST = UTC-7 hours DOY022=1/22)

SPACECRAFT COMMANDING:

There were 8 command files radiated to the S/C during this period. The total files radiated since launch is now 3188. These commands were sent in support of the following activities:

Nominal drag pass sequences (P1124, P1136)

Nominal corridor control maneuver sequences (None)

Command loss timer resets

Contingency mode drag duration parameter = 900 seconds

Battery VT level set to 6 shifted

Last Orbit Covered by this Report = 1122

Total Phase I Aerobraking orbits accomplished = 180

Total Phase II Aerobraking orbits accomplished = 547

Total Science Phasing orbits accomplished = 290

Apoapsis altitude = 2222.2 km
Apoapsis altitude decrease since start of aerobraking = 51803.6 km

Periapsis altitude = 105.6 km

Current Orbit Period = 02:34:52
Orbit Period decrease since start of aerobraking = 42:24:41

Starting Phase II orbit period = 11:38:02

RECENT EVENTS:

The Mars Global Surveyor spacecraft continues excellent aerobraking performance. About 6.5 minutes have been removed from the orbit period in the past 18 drag passes. The apoapsis altitude has been dropping at the rate of 13.5 km per drag pass which is very close to the plan of 13.1 km. The dynamic pressure 9-orbit running mean is now 0.187 N/m2 and is predicted to go lower without the need for a periapsis raise maneuver. The desired average dynamic pressure for this week is 0.136 N/m2. No corridor control maneuvers have been required. Predictions show low dynamic pressures this week even though periapsis altitudes continue to cycle lower. Projections still show the walkout beginning on 1/30 - 1/31.

Currently, sequence P1117 is controlling the S/C activities. It will be replaced later this afternoon with P1124 which will control activities starting with orbit 1124 through orbit 1133. Two backup orbits were executed this period when sequence build errors for sequence P1115 forced execution of orbits 1115 and 1116 from the P1106 sequence. All sequences contained 9 primary and 4 backup orbits to maintain a prime shift built, once per day. Starting with sequence P1124, all sequences will contain 10 primary and 5 backup orbits. All periapsis timing predictions have been very good therefore no special, non-scheduled sequences were required.

New sequence parameters were presented today at the Reset 20 meeting. Several changes were required to accommodate the shrinking orbit period to prevent old sequence activities from colliding with new sequence commands. Among the changes was the removal of the second engineering playback, shortening the catbed heater warm-up time and shortening the power generation maneuver.

Subsystems continue to report excellent S/C health and performance. The -Y solar array yoke has shown no change in structural performance. Attitude knowledge has been maintained throughout the period with excellent star processing. The power subsystem reports strong performance with battery discharge depths still reaching 32% each drag pass with 31% being contributed due to the 37 minute eclipse. The minimum MOLA laser temperature observed this period was 11.5°C with a slight upward trend observed due to the decreasing orbit period. The telecommunications subsystem continues solid performance. One uplink file, P1117, was radiated twice due to ground transmitter problems.

UPCOMING EVENTS:

Periapsis for Orbit 1123 DOY020/20:22:02 Through
Periapsis for Orbit 1141 DOY022/17:48:44 UTC

(Note: MST = UTC-7 hours DOY020=1/20)

SPACECRAFT COMMANDING:

There were 8 command files radiated to the S/C during this period. The total files radiated since launch is now 3180. These commands were sent in support of the following activities:

Nominal drag pass sequences (P1106, P1117)

Nominal corridor control maneuver sequences (None)

Nominal star catalog and ephemeris file updates

Last Orbit Covered by this Report = 1104

Total Phase I Aerobraking orbits accomplished = 180

Total Phase II Aerobraking orbits accomplished = 529

Total Science Phasing orbits accomplished = 290

Apoapsis altitude = 2470.8 km
Apoapsis altitude decrease since start of aerobraking = 51555.1 km

Periapsis altitude = 106.5 km

Current Orbit Period = 02:41:21
Orbit Period decrease since start of aerobraking = 42:18:12

Starting Phase II orbit period = 11:38:02

RECENT EVENTS:

The Mars Global Surveyor spacecraft continues excellent aerobraking performance. Over 12.5 minutes have been removed from the orbit period in the past 35 drag passes. The Navigation Team has been tracking performance in terms of apoapsis altitude reduction rather than per orbit dynamic pressure or period reduction. The apoapsis altitude has been dropping at the rate of 13.5 km per drag pass compared to the desired decay rate for the reset 19 period 14.4 km per pass. The dynamic pressure 9-orbit running mean is now 0.188 N/m2 which is a little higher than the original baseline predicted, but is required to maintain the current desired trajectory. A periapsis lowering maneuver was ordered for the apoapsis portion of orbit 1104 but was removed from the uplink queue when later drag results showed more favorable apoapsis reduction. To maintain the desired apoapsis reduction, dynamic pressures of about 0.17 N/m2 must be averaged through this reset period. Predictions continue to show very slight increase in atmospheric density for the coming 2 weeks, even though the periapsis altitude continues to cycle lower

Currently, sequence P1097 is controlling the S/C activities. It will be replaced later this afternoon with P1106 which will control activities starting with orbit 1106 through orbit 1114. No backup orbits were executed this period. All sequences will contained 9 primary and 4 backup orbits to maintain a prime shift built, once per day. All periapsis timing predictions have been very good therefore no special, non-scheduled sequences were required.

Subsystems continue to report excellent S/C health and performance. The -Y solar array yoke has shown no change in structural performance. Attitude knowledge has been maintained throughout the period with excellent star processing. The power subsystem reports strong performance with battery discharge depths still reaching 32% each drag pass with 31% being contributed due to the 37 minute eclipse. The minimum MOLA laser temperature observed this period was 11.5°C with a slight upward trend observed due to the decreasing orbit period. The telecommunications subsystem continues solid performance although one file (P1071) radiated to the S/C this period required re-transmitting due to bit errors. There is no indication of any S/C or ground equipment problems and it is believed that the cause of the bit errors may be due to degrading station predicts as the orbit timing drifts coupled with shorter orbits.

UPCOMING EVENTS:

Periapsis for Orbit 1105 DOY018/20:58:23 Through
Periapsis for Orbit 1122 DOY020/17:46:44 UTC

(Note: MST = UTC-7 hours DOY018=1/18)

SPACECRAFT COMMANDING:

There were 9 command files radiated to the S/C during this period. The total files radiated since launch is now 3172. These commands were sent in support of the following activities:

Nominal drag pass sequences (P1071, P1080, P1088, P1097)

Nominal corridor control maneuver sequences (None)

Command loss timer resets

Last Orbit Covered by this Report = 1069

Total Phase I Aerobraking orbits accomplished = 180

Total Phase II Aerobraking orbits accomplished = 494

Total Science Phasing orbits accomplished = 290

Apoapsis altitude = 2944.8 km
Apoapsis altitude decrease since start of aerobraking = 51081.1 km

Periapsis altitude = 107.5 km

Current Orbit Period = 02:53:58
Orbit Period decrease since start of aerobraking = 42:05:35

Starting Phase II orbit period = 11:38:02

RECENT EVENTS:

The Mars Global Surveyor spacecraft continues excellent aerobraking performance. Over 10 minutes have been removed from the orbit period in the past 24 drag passes. Period reduction progress continues slightly ahead of plan. The dynamic pressure 9-orbit running mean is now 0.188 N/m2 which is a little higher than desired. A corridor control maneuver was ordered and successfully executed at the apoapsis portion of orbit 1069 which raises periapsis to reduce the average drag force. The project is attempting to maintain about 0.15 N/m2 average dynamic pressure through this week without watching corridor low and high limits. Predictions show very slight increase in atmospheric density for the coming 2 weeks, even though the periapsis altitude continues to cycle lower. The ‘flare’ maneuver discussed earlier was not needed. This maneuver was intended to slow aerobraking slightly, but now navigation analysis indicates that the aerobraking walk-out period can begin on about 1/31/99, 5 days earlier than the original baseline. The profile for the remainder of aerobraking shows a 3 - 5 day walk-out period with daily periapsis raise maneuvers until the Aerobraking Exit (ABX) maneuver execution on 2/4/99 - 2/5/99. The target orbit period for the ABX is 112 minutes with the Local Mean Solar Time (LMST) between 2:04 am and 2:02 am.

Currently, sequence P1063 is controlling the S/C activities. It will be replaced later this afternoon with P1071 which will control activities starting with orbit 1071 through orbit 1079. No backup orbits were executed this period. The P1047 and P1055 sequence builds contained 8 primary and 4 backup orbits. Starting with P1063, all sequences will contain 9 primary and 4 backup orbits to maintain a prime shift built, once per day. All periapsis timing predictions have been very good therefore no special, non-scheduled sequences were required. The Navigation team now predicts 12 orbits that meet periapsis timing limitations. The first 3 predicted orbits are not used due to the latency in Nav team and S/C team processing time.

Subsystems continue to report excellent S/C health and performance. The -Y solar array yoke has shown no change in structural performance. Attitude knowledge has been maintained throughout the period with excellent star processing. The power subsystem reports strong performance with battery discharge depths now about 32% each drag pass. Since Wednesday’s reset meeting, the exciter is being powered off during the Earth occultation period to preserve energy. The solar eclipse period continues to grow longer each orbit, now at 36 minutes. The minimum MOLA laser temperature observed this period was 10.9°C. The telecommunications subsystem continues solid performance.

UPCOMING EVENTS:

Periapsis for Orbit 1070 DOY014/19:15:09 Through
Periapsis for Orbit 1104 DOY018/17:48:29 UTC

(Note: MST = UTC-7 hours DOY014=1/14)

SPACECRAFT COMMANDING:

There were 9 command files radiated to the S/C during this period. The total files radiated since launch is now 3163. These commands were sent in support of the following activities:

Nominal drag pass sequences (P1047, P1055, P1063)

Nominal corridor control maneuver sequences (A1069)

Command loss timer resets

Star catalog and ephemeris use commands

Planned parameter change to increase the C’Mode Drag Duration

Last Orbit Covered by this Report = 1045

Total Phase I Aerobraking orbits accomplished = 180

Total Phase II Aerobraking orbits accomplished = 470

Total Science Phasing orbits accomplished = 290

Apoapsis altitude = 3323.0 km
Apoapsis altitude decrease since start of aerobraking = 50703 km

Periapsis altitude = 108.9 km

Current Orbit Period = 03:04:14
Orbit Period decrease since start of aerobraking = 41:55:19

Starting Phase II orbit period = 11:38:02

RECENT EVENTS:

The Mars Global Surveyor spacecraft continues excellent aerobraking performance. Eight and one half minutes have been removed from the orbit period in the past 21 drag passes. Period reduction progress continues as planned. The dynamic pressure 8-orbit running mean is now 0.168 N/m2 which is just inside the desired corridor, 0.11 N/m2 to 0.17 N/m2. There were no corridor control maneuvers ordered. Predictions show very slight increase in atmospheric density for the coming 2 weeks, even though the periapsis altitude continues to cycle lower. A ‘flare’ maneuver is being planned for execution that will accommodate the earlier arrival at the desired orbit period. This will be a corridor control maneuver with a custom delta V magnitude that is intended to accommodate the 2 am Local Solar Time (LST) simultaneous with the 112 minutes desired orbit period.

Currently, sequence P1039 is controlling the S/C activities. It will be replaced later this afternoon with P1047 which will control activities starting with orbit 1047 through orbit 1054. No backup orbits were executed this period. All sequences built this period had 8 primary orbits and 4 backups to maintain a primary shift build schedule. All periapsis timing predictions have been outstanding therefore no special, non-scheduled sequences were required.

Subsystems continue to report excellent S/C health and performance. The -Y solar array yoke has shown no change in structural performance. Because of the reduced drag force through this period of aerobraking concern has lessened over the overall panel structural health, however, there are still 280 orbits left and the team continues to monitor the panel strength closely. Attitude knowledge has been maintained throughout the period with excellent star processing. The power subsystem reports strong performance with battery discharge depths now about 31% each drag pass. The primary chargers at V/T level 7 are able to fully recharge the batteries with 10 minutes to spare. As the orbit period continues to shrink, the V/T level will be reduced to provide a faster charge. The solar eclipse period continues to grow longer each orbit, now at 34 minutes. The minimum MOLA laser temperature observed this period was 10.9°C, down slightly due to the increasing eclipse period. The minimum solar array temperatures are now reaching -134°C and the HGA gimbal is a warm 25° with it’s heater on full time. The telecommunications subsystem continues solid performance.

UPCOMING EVENTS:

Periapsis for Orbit 1046 DOY011/19:39:47 Through
Periapsis for Orbit 1061 DOY013/16:56:14 UTC

(Note: MST = UTC-7 hours DOY008=1/8)

SPACECRAFT COMMANDING:

There were 9 command files radiated to the S/C during this period. The total files radiated since launch is now 3154. These commands were sent in support of the following activities:

Nominal drag pass sequences (P1024, P1031, P1039)

Nominal corridor control maneuver sequences (none)

Command loss timer resets

Star catalog and ephemeris file loads

Last Orbit Covered by this Report = 1024

Total Phase I Aerobraking orbits accomplished = 180

Total Phase II Aerobraking orbits accomplished = 449

Total Science Phasing orbits accomplished = 290

Apoapsis altitude = 3629.0 km
Apoapsis altitude decrease since start of aerobraking = 50397 km

Periapsis altitude = 110.3 km

Current Orbit Period = 03:12:44
Orbit Period decrease since start of aerobraking = 41:46:49

Starting Phase II orbit period = 11:38:02

RECENT EVENTS:

The Mars Global Surveyor spacecraft continues excellent aerobraking performance. Just under 5 minutes have been removed from the orbit period in the past two days (14 orbits). As projected, about 20 seconds are removed each pass. The dynamic pressure 8-orbit running mean is now 0.123 N/m2 which is inside the desired corridor, 0.11 N/m2 to 0.17 N/m2. There were no corridor control maneuvers ordered. Predictions show very slight increase in atmospheric density for the coming 2 weeks, even though the periapsis altitude continues to cycle lower.

Currently, sequence P1016 is controlling the S/C activities. It will be replaced later this afternoon with P1024 which will control activities starting with orbit 1024 through orbit 1030. No backup orbits were executed this period. All sequences built this period had 8 primary orbits and 4 backups to maintain a primary shift build schedule. All periapsis timing predictions have been outstanding therefore no special, non-scheduled sequences were required.

Subsystems continue to report excellent S/C health and performance. The -Y solar array yoke has shown no change in structural performance. No panel deflection data is available due to the S/C attitude during the drag pass, but the structural frequency continues to show no degradation in strength. Attitude knowledge has been maintained throughout the period with excellent star processing. The power subsystem reports strong performance with battery discharge depths now about 30% each drag pass and increasing slower than last period. The power generation maneuver that holds the panels directly on the sun vector for 40 minutes each orbit, assures full battery recharge. The solar eclipse period continues to grow longer each orbit, now at 32 minutes. The minimum MOLA laser temperature observed this period was 11.5 °C down slightly due to the increasing eclipse period. Other S/C components are being subjected to colder temperatures due to the eclipse, but all are safe. The telecommunications subsystem continues solid performance.

UPCOMING EVENTS:

Periapsis for Orbit 1023 DOY008/19:21:24 UTC Through
Periapsis for Orbit 1045 DOY008/16:27:17 UTC

(Note: MST = UTC-7 hours DOY008=1/8)

SPACECRAFT COMMANDING:

There were 4 command files radiated to the S/C during this period. The total files radiated since launch is now 3145. These commands were sent in support of the following activities:

Nominal drag pass sequences (P1009, P1016)

Nominal corridor control maneuver sequences (none)

Command loss timer resets

Last Orbit Covered by this Report = 1008

Total Phase I Aerobraking orbits accomplished = 180

Total Phase II Aerobraking orbits accomplished = 435

Total Science Phasing orbits accomplished = 290

Apoapsis altitude = 3794 km
Apoapsis altitude decrease since start of aerobraking = 50232 km

Periapsis altitude = 112.1 km

Current Orbit Period = 03:17:25
Orbit Period decrease since start of aerobraking = 41:42:08

Starting Phase II orbit period = 11:38:02

RECENT EVENTS:

The Mars Global Surveyor spacecraft continues excellent aerobraking performance. Over the past 29 orbits 11 minutes, 50 seconds were removed from the orbit period. Each periapsis pass reduces the orbit period by about 25 seconds versus the planned 22 seconds. Current predictions presented in the reset 18 meeting today show the margin gained against the original aerobraking baseline to date will enable the walk out start to begin 2 days earlier, on February 2. The dynamic pressure 8-orbit running mean is now 0.113 N/m2 which is inside the desired corridor, 0.11 N/m2 to 0.17 N/m2. One periapsis raise maneuver was ordered this period for the apoapsis portion of orbit 1000 to steer the dynamic pressure back into the corridor.

Currently, sequence P1002 is controlling the S/C activities. It will be replaced later this afternoon with P1009 which will control activities starting with orbit 1009 through orbit 1015. No backup orbits were executed this period. All sequences built this period had 7 primary orbits and 4 backups to maintain a primary shift build schedule. Starting with P1009, all sequences will contain commands for 8 primary orbits and 4 backups. The Navigation team predicts 10 orbit periapsis times for sequence builds of which the first two are not used. Incorporation of a new wave model by the Navigation team has improved periapsis timing predictions allowing for no special sequence builds during this period.

The reset 18 meeting today approved new parameters to allow for a longer power generation maneuver, now up to 40 minutes. The science data playbacks are being executed during the apoapsis period and are lost when a corridor control maneuver is performed.

Subsystems continue to report excellent S/C health and performance. The -Y solar array yoke has shown no change in structural performance. No panel deflection data is available due to the S/C attitude during the drag pass, but the structural frequency still shows no degradation in strength. Attitude knowledge has been maintained throughout the period with excellent star processing. The power subsystem reports strong performance with battery discharge depths now about 27% each drag pass with the 40 minutes power generation maneuver easily making up the deficit. The solar eclipse period continues to grow longer each orbit, now at 30 minutes. Commands to switch the primary charger operation to V/T level 8 were uplinked this period to prevent any battery overcharge and overheating. The battery 2 charger operation is now normal since the eclipse occurs each orbit. The minimum MOLA laser temperature observed this period was 13.0 °C down slightly due to increasing eclipse period. The warming maneuver duration has been increased to 40 minutes per orbit to assure the instrument temperature does not fall too low. Solar array minimum temperatures are now reaching -120°C during the eclipse portion of the orbit. The telecommunications subsystem continues solid performance.

With the orbit period shrinking and the eclipse period increasing, energy balance becomes the largest concern as phase 2 aerobraking comes to an end. Predictions show just enough energy to maintain full battery charge each orbit at the end of aerobraking.

UPCOMING EVENTS:

Periapsis for Orbit 1009 DOY006/21:51:56 UTC Through
Periapsis for Orbit 1022 DOY008/16:07:32 UTC

(Note: MST = UTC-7 hours DOY006=1/6)

SPACECRAFT COMMANDING:

There were 15 command files radiated to the S/C during this period. The total files radiated since launch is now 3141. These commands were sent in support of the following activities:

Nominal drag pass sequences (P981, P988, P995, P1002)

Nominal corridor control maneuver sequences (A1000)

Command loss timer resets

Battery VT-Curve commands

Nominal star catalog and ephemeris file updates

Last Orbit Covered by this Report = 979

Total Phase I Aerobraking orbits accomplished = 180

Total Phase II Aerobraking orbits accomplished = 406

Total Science Phasing orbits accomplished = 290

Apoapsis altitude = 4216 km
Apoapsis altitude decrease since start of aerobraking = 49810 km

Periapsis altitude = 109.0 km

Current Orbit Period = 03:29:15
Orbit Period decrease since start of aerobraking = 41:30:18

Starting Phase II orbit period = 11:38:02

RECENT EVENTS:

The Mars Global Surveyor spacecraft continues excellent aerobraking performance. Each periapsis pass reduces the orbit period by about 29 seconds which is nearly consistent with the reset 17 trajectory. Currently, the period is about 5.6 minutes ahead of the baseline. The dynamic pressure 8-orbit running mean is now 0.183 N/m2 which is outside the desired corridor, 0.11 N/m2 to 0.17 N/m2. One periapsis raise maneuver was ordered this period for the apoapsis portion of orbit 979 to steer the dynamic pressure back into the corridor.

Currently, sequence P974 is controlling the S/C activities. It will be replaced later this afternoon with P981 which will control activities starting with orbit 981 through orbit 987. No backup orbits were executed this period. Except for sequences P955 and P961, all sequences built this period had 7 primary orbits and 4 backups to maintain a primary shift build schedule. The current sequence builds use 4 backup orbits to assure safe S/C operations in case of a station outage preventing uplink of a new sequence. A clear all scoreboards command was radiated prior to uplink of P955 to clean-up the flight software accounting of sequence messages due to the previously aborted uplink attempt of P953. Incorporation of a new wave model by the Navigation team has improved periapsis timing predictions allowing for no special sequence builds during this period.

The reset 17 meeting this week approved new parameters to support the onset of solar eclipse. A new contingency mode script was loaded that will enable use of an eclipse entry script to manage solar array pointing during non-drag periods to maintain energy balance. Because of the onset of eclipses, entry into Safe Mode has been disabled by fault responses other than simultaneous processor hardware failures.

The backup processor, SCP2, was recovered from contingency mode successfully, as planned. The higher rate accelerometer data and other -Y solar array panel data is once again available.

Having SCP2 operating the aerobraking sequence along with the control SCP provides redundancy in case a processor hardware failure occurs on SCP1 without invoking contingency mode. The capability for a seamless transition to the backup SCP is once again possible.

Subsystems continue to report excellent S/C health and performance. The -Y solar array yoke has shown no change in structural performance. The +Y solar array panel is now positioned with the cell side into the velocity vector just as is the -Y array with the gimbal powered hold commands in force. This was required to provide energy during the pass to maintain energy balance during the latter part of aerobraking.

Attitude knowledge has been maintained throughout the period with excellent star processing. The power subsystem reports strong performance with battery discharge depths now about 20% each drag pass with the 35 minutes power generation maneuver easily making up the deficit. The DoD is expected to increase as the eclipse duration increases, now about 20 minutes. Battery 2 charger operation has improved now that the eclipse season is upon us. CCR-231 approved V/T level commands to help control under/over charging of the batteries, particularly to prevent battery overheating caused by the V/T level set too low. The primary battery chargers are now connected at all times. Commands have been sent to manually set the V/T curve settings to level 6. The minimum MOLA laser temperature observed this period was 14.0 °C now being warmed by the Earth pointed power generation maneuver that’s being performed each orbit. As the eclipse period increases the minimum temperatures is expected to decrease further. Extending the warming period is an option if the trend shows the MOLA laser is getting too cold. The telecommunications subsystem continues solid performance.

UPCOMING EVENTS:

Periapsis for Orbit 980 DOY002/19:49:15 UTC Through
Periapsis for Orbit 1008 DOY006/18:42:29 UTC

(Note: MST = UTC-7 hours DOY002=1/2)

SPACECRAFT COMMANDING:

There were 22 command files radiated to the S/C during this period. The total files radiated since launch is now 3126. These commands were sent in support of the following activities:

Nominal drag pass sequences (P955, P961, P968, P974)

Nominal corridor control maneuver sequences (A979)

Command loss timer resets

Reset SCP2 C’Mode’Active’Flag

SCP2 C’Mode recovery commands

Battery VT-Curve commands

Full SCP memory read out

Clear all scoreboards

Safe’Mode disable

New C’Mode script, AEM script and pointers

MSOP-MGS Aerobraking Status Reports for 1998