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Mission Operations Days: 2003/347 to 2003/353
December 13, 2003 00:00:00 GMT to December 19, 2003 00:00:00 GMT

There was an anomaly with the Terra ACE-B on December 16, 2003 (DOY 2003/350).
The spacecraft and all instruments were transitioned to Safe Mode.
See Non-MODIS Significant Events below for details.

Terra Spacecraft and MODIS Instrument Status:

AM-1 "Terra" is in Safe Mode
PFM MODIS is in Safe Mode
(PS1, CPA, and TG1 are Powered and Cross Strapped with FR B)
Component State(s) Comment
Blackbody A Off; B Off Safe Mode
Calibration Electronics A Off; B Off Safe Mode
Control Processor A On; B Off Safe Mode
Nadir Door Unlatched, Closed Safe Mode
Space View Door Unlatched, Closed Safe Mode
Solar Diffuser Door Unlatched, Screened Permanent Configuration
FDDI Formatter A Off; B Off Safe Mode
FDDI Port A Off; B Off Safe Mode
FIFO Memory #1 & #2 Off; #3 & #4 Off Safe Mode
Format Processor A Off; B On Safe Mode
Power Supplies #1 On, #2 Off Safe Mode
PV VIS FPA A Off; B Off Safe Mode
PV NIR FPA A Off; B Off Safe Mode
PV SMIR FPA A Off; B Off Safe Mode
PV LWIR FPA A Off; B Off Safe Mode
PC LWIR FPA A Off; B Off Safe Mode
RC Outgas Heaters All 3 (CS, IS, OS) Off Safe Mode
RC LWIR FPA Heater Off (not controlling) Safe Mode
RC SMIR FPA Heater Off Safe Mode
Scan Assembly A Off; B Off Safe Mode
SDSM Off Safe Mode
SRCA Off Safe Mode
PS1 Survival Heater Enabled Safe Mode
PS2 Survival Heater Enabled Safe Mode
Timing Generator A On; B Off Safe Mode
Flight Software Rev BD + 11 sets of patches
  • CP07 to Survival Mode - No SDD to closed command (1 patch)
  • CP07 to Safe Mode - No FR OFF Command (1 patch)
  • CP07 to Safe Mode - No SDD to closed command (1 patch)
  • CP07 to Science Mode - Turn on FRB instead of FRA (1 patch)
  • CP07 to Outgas and Science Mode - Turn on FRB instead of FRA (1 patch)
  • FR Error Counting and Statistics (2 patches)
  • FR 1000ms time code patches (3 patches)
  • FR Band 5 Gain Change (20 commands)
  • FR BB Ideal Output Values (1 patch)
  • FR A EEPROM KME Fast 1 word patch (1 patch)
  • FR B EEPROM KME Fast 1 word patch (1 patch)
Safe Mode
Inhibit Ids Set 32, 33, 54 Safe Mode
TMON 66 Disabled Safe Mode
TMON 67 Disabled Safe Mode
TMON 68 Enabled Safe Mode
TMON 69 Disabled Safe Mode

This Week’s Completed MODIS Activities:

Saturday, December 13, 2003

PFM Lunar Calibration via spacecraft roll maneuver (-6.4083 degrees)
2003/347 16:52:40 ATC MOD_OA03_FR_DAY_RATE
2003/347 ??:??:?? Real-Time Terra FOT commands S/C to low-fidelity pointing
2003/347 17:38:45 ATC MOD_OA03_FR_NIGHT_RATE (03:23 early)
2003/347 18:12:33-18:19:19 ATC MOD_OA08_ROLL_MAN
2003/347 ??:??:?? Real-Time Terra FOT commands S/C to high-fidelity pointing
2003/347 18:34:56 ATC MOD_OA03_FR_DAY_RATE (03:23 late)
2003/347 19:21:01 ATC MOD_OA03_FR_NIGHT_RATE

Sunday, December 14, 2003


Monday, December 15, 2003


Tuesday, December 16, 2003

2003/350 13:04:09 ACE-B Anomaly, Safe Mode Transition

Wednesday, December 17, 2003


Thursday, December 18, 2003


Friday, December 19, 2003


This Week’s Scheduled MODIS Activities Not Completed:


Upcoming MODIS Events:

None scheduled prior to spacecraft recovery from Safe Mode.

MODIS planned recovery activities, once the spacecraft returns to Normal/Science Mode (all will be Real-Time procedures):

Standby Transition, CP Door Table Dump, SVD Opened, CP Door Table Dump:

CFPA cool down takes approximately 48 hours during which time we may perform 3 instances of SDSM Calibrations:

After the CFPA's have cooled down to around 83K, the Black Body will be powered and set to 290K:

Blackbody warm up will take about 5 hours.

NAD Open, CP Door Table Dump:

Additional calibrations (ATC stored or Real-Time) may be scheduled while the NAD is closed to make use of the rare unlit cavity situation, pending MCST inputs.


The next Lunar Calibration will occur on DOY 2004/012 (January 12, 2004), with a data collect time from 08:19:02 to 08:25:32. The necessary roll angle is - 0.2827 degrees. This is a small enough angle that the moon may be viewed through the Space View Port (SVP) without needing the spacecraft to perform a roll. Therefore, no roll will be performed for this calibration. However, the MODIS data will be adjusted for Day Rate and Sector Rotation as is standard for a Lunar Calibration.

MODIS Anomalies:

Terra SSR Anomaly:

Although not directly the result of a MODIS problem, the most recent Printed Wire Assembly (PWA) failures in the Terra Solid State Recorder (SSR) do affect MODIS data. See the Non-MODIS Significant Events section below for more details.

Terra SFE Anomaly:

Although not directly the result of a MODIS problem, the SFE anomaly is causing an unrecoverable loss of all current MODIS Direct Broadcast data. Normal science data recording and playbacks are functioning properly. See the Non-MODIS Significant Events section below for more details.

Terra ACE Anomaly and Safe Mode:

MODIS was commanded to Safe Mode by the Terra ACE Anomaly. No Science Data is produced in this configuration. See the Non-MODIS Significant Events section below for more details.

General Instrument Comments:

MODIS is in Safe Mode, using all A-side components, but cross-strapped to Formatter B. All subsystems are powered off except for the Power Supply 1, Control Processor A, Timing Generator A, and Formatter B. The Solar Diffuser Door remains at the Screened position. The Space View Door and Nadir Aperture Door were closed as part of the Safe Mode transition.

MODIS Telemetry Trends:

The Cold Focal Planes Assemblies (CFPAs) in the Radiative Cooler are warming to their SVD Closed plateau of 240K. The internal electronics are cooling and the blackbody is off and cooled below the telemetry range of 269K. Door performance for the Science to Safe transition was as expected (triggers and step counts).

Non-MODIS Significant Events:

Terra Solid State Recorder Anomaly


The SSR Anomaly is still under investigation. MODIS currently is operating with 34 Supersets allotted for its buffer. There are plans in the works for possibly power cycling the SSR to get back PWA’s that are in the Bad List, but no date has yet been set. There are no current plans for a change in science data capture rates. For details, see previous reports.

Terra SFE Anomaly


The SFE-A on Terra is corrupting every fourth byte of data it produces for the DAS-1 feed to the Direct Broadcast equipment. For details, see previous reports.

Additional Information:

With the occurrence of the ACE Anomaly and Safe Mode transition, the recovery of the SFE has been postponed pending initial recovery of the spacecraft to its Normal Mode.

Terra ACE Anomaly and Safe Mode


The Terra spacecraft and instruments were commanded to Safe Mode after the FDIR was tripped due to questionable data being received by the GNC subsystems. The anomaly is currently under investigation. See below for details.


The Terra FOT has determined that the Safe Hold may have been caused due to problems within the Guidance Navigation and Control (GNC) Bus Data Unit (BDU). The Inertial Reference Unit (IRU) (where the 3 gyros are kept) saw 5 bad data samples (outside of acceptable limits) and the Fault Detection Isolation and Recovery (FDIR) made it go into Safe Mode. However, there were 2 good samples seen just prior to going into Safe Mode, but it was too late for the FDIR to stop what it was doing. There is still no word yet on what the cause was for the bad data samples (another SEU?), but the FOT is looking into the serial interface between the BDU and Attitude Control Electronics (ACE). In its current state, the spacecraft is operating on minimal fault management. There is a pressing need to regain some (if not all) functionality from the GNC components and restore FDIR operations. Once under FDIR control, the spacecraft and instruments have several additional "layers" of autonomous protection.

The current plan, scheduled for Saturday, December 20, 2003 (DOY 2003/54), is to switch control over from ACE-A Safe Mode to ACE-B Safe Mode. ACE-B was the component that saw the suspicious telemetry in the IRU that the FDIR keyed off of to initiate the Safe Mode transition. If ACE-B is totally nonfunctional on power up, the spacecraft will be switched back to ACE-A. The switch back would be via Real-Time commanding backed up by a redundant set of stored command sequences on a count down timer should commanding communication be lost once the initial transition is made. If ACE-B is giving bad data, yet still functional and able to maintain itself, a memory monitor patch will to grab as much digital data as possible for a few orbits, and then Terra will be switched back to ACE-A. If ACE-B appears to be okay and it is not giving bad data, it will be monitored for several orbits. If it is stable, then the FDIR may be re-enabled so that there is some fault management backup, but the spacecraft will remain in SAFE mode. The spacecraft will be monitored over the weekend and a plan from there will be developed.

The Memory Monitor will be enabled *prior* to switching over to ACE-B. This will allow for a much finer resolution on the telemetry sampling that was tied to the initial Safe Mode transition. The Memory Monitor runs external to the ACE Hardware and is unaffected by whatever the state is when the ACE-B is powered. Its use is an attempt to gain additional telemetry, should a repeat anomaly on ACE-B occur. The data will be used to troubleshoot this anomaly.

There is no estimate yet as to when Science Mode will be restored.

The EMOS mission status webpage (which includes instrument data loss records) can be found at the following URL. Note that a password is now required to access the EOS mission links web pages. There are directions at the URL below for how to obtain a username/password.

Limited Life Item Status:

SRCA 10W Lamp #1: 222.7 of 500 hours
SRCA 10W Lamp #2: 163.5 of 500 hours
SRCA 10W Lamp #3: 172.7 of 500 hours
SRCA 10W Lamp #4: 62.2 of 500 hours

SRCA 1W Lamp #1: 564.9 of 4000 hours
SRCA 1W Lamp #2: 276.7 of 4000 hours

Solar Diffuser Door: 2146 of 3022 Movements
Nadir Aperture Door: 537 of 1316 Movements
Space View Door: 440 of 1316 Movements