Mission Operations Days: 2003/333 to 2003/339
November 29, 2003 00:00:00 GMT to December 05, 2003 00:00:00 GMT
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There was an anomaly with the Terra SFE on November 30, 2003 (DOY 2003/334).
See Non-MODIS Significant Events below for details.
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Terra Spacecraft and MODIS Instrument Status:
| AM-1 "Terra" is in Normal Mode PFM MODIS is in A-Side Nominal Science Mode (Cross Strapped with FR B) |
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|---|---|---|
| Component | State(s) | Comment |
| Blackbody | A On (290K); B Off | Nominal Science Mode |
| Calibration Electronics | A On; B Off | Nominal Science Mode |
| Control Processor | A On; B Off | Nominal Science Mode |
| Nadir Door | Unlatched, Open | Nominal Science Mode |
| Space View Door | Unlatched, Open | Nominal Science Mode |
| Solar Diffuser Door | Unlatched, Screened | Permanent Configuration |
| FDDI Formatter | A On; B Off | Nominal Science Mode |
| FDDI Port | A On; B Off | Nominal Science Mode |
| FIFO Memory | #1 & #2 On; #3 & #4 Off | Nominal Science Mode |
| Format Processor | A Off; B On | Nominal Science Mode |
| Power Supplies | #1 On, #2 Off | Nominal Science Mode |
| PV VIS FPA | A On; B Off | Nominal Science Mode |
| PV NIR FPA | A On; B Off | Nominal Science Mode |
| PV SMIR FPA | A On; B Off | Nominal Science Mode |
| PV LWIR FPA | A On; B Off | Nominal Science Mode |
| PC LWIR FPA | A On; B Off | Nominal Science Mode |
| RC Outgas Heaters | All 3 (CS, IS, OS) Off | Nominal Science Mode |
| RC LWIR FPA Heater | On (83K) | Nominal Science Mode |
| RC SMIR FPA Heater | Off | Nominal Science Mode |
| Scan Assembly | A On; B Off | Nominal Science Mode |
| SDSM | Off | Nominal Science Mode |
| SRCA | Off | Nominal Science Mode |
| PS1 Survival Heater | Enabled | Nominal Science Mode |
| PS2 Survival Heater | Enabled | Nominal Science Mode |
| Timing Generator | A On; B Off | Nominal Science Mode |
| Flight Software | Rev BD + 11 sets of patches
|
Nominal Science Mode |
| Inhibit Ids Set | none | Nominal Science Mode |
| TMON 66 | Disabled | Nominal Science Mode |
| TMON 67 | Disabled | Nominal Science Mode |
| TMON 68 | Enabled | Nominal Science Mode |
| TMON 69 | Disabled | Nominal Science Mode |
This Week’s Completed MODIS Activities:
Saturday, November 29, 2003
None
Sunday, November 30, 2003
2003/334 12:50:54 SFE-A DAS-1 Anomaly
Monday, December 1, 2003
None
Tuesday, December 2, 2003
2003/336 20:17:50-20:26:38 ATC MOD_OA16_SDSM_SCRN_NO_DOOR_A.4 OA-16: SD/SDSM screened side A, no door movement
Wednesday, December 3, 2003
None
Thursday, December 4, 2003
None
Friday, December 5, 2003
FR Test Packet Diagnostic Test to aid SFE-A Anomaly Analysis
2003/339 16:10:11-16:10:50 Real-Time mod_sci_abnorm('abnorm')
2003/339 16:11:05-16:11:49 Real-Time mod_fr_packet('test')
2003/339 16:13:55-16:14:32 Real-Time mod_fr_packet('normal')
2003/339 16:14:41-16:15:16 Real-Time mod_sci_abnorm('norm')
The period when MODIS was flagging its science data as abnormal:
2003/339 16:10:29-16:14:51 (4 minutes, 22 seconds)
The period when MODIS was generating test packets:
2003/339 16:11:29-16:14:12 (2 minutes, 43 seconds)
This Week’s Scheduled MODIS Activities Not Completed:
None
Upcoming MODIS Events:
Possible further diagnostic test to support the SFE Anomaly Resolution (see Non-MODIS Significant Events section below for more details).
Monday, December 8, 2003
2003/343 20:26:58-20:35:46 ATC MOD_OA16_SDSM_SCRN_NO_DOOR_A.4 OA-16: SD/SDSM screened side A, no door movement
2003/343 21:16:26-21:37:21 ATC MOD_OA20_SRCA_10W_RAD_A_Base.2 OA-20: SRCA 10W Continuous Radiometric - A Side, Using Lamp #1
Data collection is from 21:32:20-21:37:21 (in S/C Night)
Maneuvers:
The next Lunar Calibration will occur on DOY 2003/347 (December 13, 2003), with a roll angle of -6.4083 degrees and a data collect time from 18:12:41 to 18:19:11.
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.
General Instrument Comments:
MODIS is in Science Mode, using all A-side components, but cross-strapped to Formatter B, with the blackbody maintained at 290K and the Solar Diffuser Door at the Screened position.
MODIS Telemetry Trends:
Nominal telemetry trending is ongoing.
Non-MODIS Significant Events:
Terra Solid State Recorder Anomaly
Overview:
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
Overview:
The SFE-A on Terra is corrupting every fourth byte of data it produces for the DAS-1 feed to the Direct Broadcast equipment. The anomaly is currently under investigation and diagnosis.
Details:
On November 30, 2003 (DOY 2003/334), at 12:50:54 GMT, the Science Formatting Equipment Side A (SFE- A) on the AM-1 "Terra" spacecraft began reporting errors. The DAS-1 (Data Access Signal #1) Channel, one of three data routes in the SFE (DAS-1, DAS-2, and KSA), was reporting Sync Errors and High-Rate Data Interface (HDI) Card Errors had occurred. This triggered a Yellow Alarm condition that notified the Flight Operations Personnel that there was a problem with the SFE. The error was caused by a failure of the data stream going through the DAS-1 matching up with the synchronization bits in the Reed-Solomon encoding it is transmitted under. At the time the errors began, Terra was in the middle of the South Atlantic Anomaly; a region of space centered over the Atlantic Ocean with increased rates of spacecraft interference from high energy particles. Past lockups of the SFE equipment (3 others since Terra's launch) have all occurred in this same region of space.
The rest of the SFE-A was functioning as expected. The two other data channels (DAS-2 and KSA) were passing data as expected. Data passing through the SFE to the Solid State Recorder (SSR) and being broadcast to TDRSS was collected and processed as expected. Science data from all instruments on Terra passed through the SFE to the SSR, and later played back to, and analyzed by, ground stations nominally. The problem with the SFE was isolated to the DAS-1 Channel.
The Terra real-time "Direct Broadcast" (DB) data comes from the SFE's DAS-1 Channel. The errors in the data stream are manifested as a corruption of every fourth byte in the stream. This corruption, in a quarter of the data stream, results in a stream that is not capable of being processed by the DB Ground Stations. Multiple ground stations from around the world all report seeing the same corrupted data stream. This data stream corruption began at the aforementioned time of the anomaly, and continues to the present. As long as the corruption continues, it is not possible for the DB Ground Stations to process the MODIS Direct Broadcast signal.
Several steps were taken to analyze the anomaly and narrow the investigation's focus. The most revealing test was that, on December 1, 2003, at 13:44:55-13:46:25 GMT, the data flow through the DAS-1 was disabled, and the DAS-1 controller began correctly generating "fill packets". These fill packets were correctly received and processed by DB Ground Stations. When the data flow through the DAS-1 was restored, the corruption of every fourth byte was again seen. This indicates that the problem in the data stream was occurring in one particular component: the DAS-1 Fist-In-First-Out (FIFO) chips, the fourth of the four FIFOs to be specific.
To aid the DB Ground Stations and GSFC data analysts in looking for patterns in the data corruption, MODIS was switched to a "test packet". This switched was performed on December 5, 2003, at 16:10-16:15 GMT. MODIS temporarily stopped producing its normal science data, and in its place, produced a repeating counter that is very easy to recognize in the data stream. After the 5 minute period, MODIS was switched back to normal science packet mode. For that period of time, no real science data was collected on MODIS. This was the third time on orbit that Terra MODIS Formatter has been commanded to “test packet” mode to aid in S/C subsystem diagnostic (2000/051-052 and 2000/228 where the previous instances). The test packet data helped the data analysts conclude that the suspect FIFO was functioning; however it was not functioning properly. This disturbance in correct operations, but not total loss of operations, is called a Single Event Upset (SEU). SEUs can occur when a high-energy particle disrupts the electronics of a spacecraft. The SFE manufacturer predicted the SFE to experience approximately 1 SEU ever year on orbit. Terra is nearing the end of its fourth year on orbit, and this is the fourth (suspected) SEU to affect the SFE.
The designed fix for an SEU on the SFE is a power cycling of the SFE. This will shut down all functions of the SFE including both DB and SSR operations. The power cycling will take approximately 15 minutes, for which time no science data will be collected, from any instrument. The planned course of action is to perform the designed power cycle of the SFE. This is predicted to restore the suspect FIFO in the DAS-1 back to its normal operational state. The prior three SFE power-recycling sequences on orbit all successfully recovered from their associated SEU conditions. The planned SFE power cycle will be identical in sequence to the most recent power cycle performed on February 2, 2003. The instruments on Terra will not change configuration for the SFE power cycle; they will all remain in their normal science mode.
Flight Operations and Hardware Provider Engineers have concluded that the SFE power cycle is a low risk activity and the appropriate action to take for this anomaly. Their findings are currently being presented to NASA management for approval.
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.
http://jupiter02.gsfc.nasa.gov/links/links.htm
Limited Life Item Status:
SRCA 10W Lamp #1: 222.6 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: 536 of 1316 Movements
Space View Door: 439 of 1316 Movements