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Terra MODIS Instrument Performance History

The Moderate Resolution Imaging Spectroradiometer (MODIS) began science data acquisition on February 24, 2000. The performance of the sensors and the on - board calibrators (the Solar Diffuser and its accompanying Solar Diffuser Stability Monitor, the Spectro - radiometric Calibration Assembly, the On - Board Calibrator Blackbody, and the Space View port) have been very good. Several features of the performance lead to characteristics in the data set that merit special attention. These items are described on this web page and links herein.

The sensor operational configuration, detector biases, and lookup table parameters are time - dependent quantities that have been changed to optimize sensor performance. Changes are documented in the metadata and many changes are accessible from the Operational Configurations links on this page.

The MODIS instrument began taking data using side - A electronics. MODIS consistently produced data starting on 24 February 2000 except for a few periods. The first occurred in April 2000 when a Terra spacecraft maneuver required that the instrument Earth View door be closed to minimize contamination. The second event occurred in August 2000. The MODIS electronics experienced a series of reset commands. Diagnostic studies lasted for nearly two weeks. The problem occurred near the time of a scheduled radiative cooler outgassing operation. The cooler outgas was completed in this period. The third period without science data spanned October 26 - 30, 2000.

Science data was processed using B - side electronics between October 30,2000 (data day 2000304) and June 15, 2001 (day 2001166). The measurements - quality during this period improved dramatically. A new set of quality flags pinpoints the few remaining noisy detectors. Several previous areas of concern have been adequately addressed in the Level 1B version 3.0 and higher releases, including:

  • Non - functional or noisy detectors
  • Optical cross - talk from Band 31 into Bands 32 through 36
  • Incomplete knowledge of time - dependent response functions for reflected solar bands (1 to 19, plus 26)
  • Presence of mirror rotation correlated noise
  • Mis - registration of 250 and 500 meter resolution bands to the 1000 meter resolution bands

The MODIS instrument experienced a Power Supply 2 (PS2 = electronics side - B) shutdown anomaly and did not take science data during the time period June 15, 2001 (day 2001166) to July 2, 2001 (day 2001183). The cause of the failure is consistent with an over - voltage shutdown most likely initiated by a high - energy radiation event that caused the Metal - oxide Semiconductor Field Effect Transistor (MOSFET) within the down - regulator of PS2 to fail.

When the MODIS recovered, it was commanded to take science mode data using Power Supply 1 and electronics side A. Science data collected since recovery show that the instrument is performing as expected. New lookup tables were constructed and implemented using post - anomaly calibrations. Code version 3.0.0 produced a consistent data set from October 30, 2000 to November 2001.

Processing using new side - A LUTs constructed using data from post - anomaly solar calibrations began July 25, 2001. The thermal leak correction switch was turned "off" in this delivery, which affects the quality of the SWIR band data (bands 5, 6, 7, 26). A new LUT delivery with the thermal leak correction turned "on" was implemented approximately September 10, 2001.

On December 13, 2001 (data day 2001347), MODIS closed its Nadir Aperture Door (NAD, i.e., the earth view door) at 14:45 UT in preparation for a Terra Inclination maneuver. The NAD re - opened at 16:29.

The Terra spacecraft entered Safe mode shortly after 15:00 UT on March 19, 2002 following the inclination adjust maneuver. MODIS began taking science data on March 28, 2002. MODIS returned to Normal mode on March 20th, 2002 at 16:35:00 UT. Shortly thereafter, MODIS was placed into Standby mode, the Space View Door was opened, and the scan mirror was started. Following the recovery, MCST noticed minor instrument performance differences that may impact the quality of products that are sensitive to mirror - side differences. Caution is warranted.

The Terra spacecraft experienced a science data loss between April 14, 2002 (15:00 UT) and April 15, 2002 (23:36 UT). The cause was a single event upset in the A - side Science Formatting Equipment. After this glitch, we continue to gather science data using A - side electronics.

The Terra MODIS Formatter has been successfully switched to the B - side. The switch necessitated a small lapse in science data production between 14:12 and 14:21 UT September 17, 2002. February 1, 2003 science data taken between 01:47:28 and 23:26:43 UT is unrecoverable.

Terra performed a Deep Space Maneuver (DSM) on March 26, 2003. MODIS performed as expected during the maneuver. The MODIS LWIR and SMIR CPFA temperatures increased between 15:01:29 UT March 26, 2003 and 07:51:41 March 27, 2003. Data during this time period is therefore suspect. Terra performed another DSM on April 14, 2003, during which time the Moon was purposely in the Earth View Port. The temperature of the cold focal planes increased starting 22:06:08 UT April 14, 2003, peaked at 94.1K at 22:29:02 UT April 14, 2003, and returned to their nominally controlled 83K temperature about 16 hours later. Data during this time period is therefore suspect.

During the May 6, 2003 (data day 2003/126) Terra Solar Diffuser calibration with the Solar Diffuser Door in the full open position, analysis by MCST determined that the solar diffuser screen remained NOT_OPEN during this calibration although the drive motor moved through the entire range of the screen from closed to open to closed. A recovery plan was implemented on July 2nd, 2003 (data day 2003/183, 17:49UT). The Solar Diffuser Door was opened but the screen was left closed. The Solar Diffuser Door will remain in this position for the remainder of the mission.

The Terra Solid State Recorder (SSR) recording was intentionally disabled from 19:25:06 through 19:33:33 UT, July 31st, 2003 (2003212). This purpose was to remove two non - functioning supersets from the active memory list. The data loss incurred during this time period is unrecoverable. SSR anomalies caused telemetry and science data loss on September 24, 2003 (2003267) from 03:30 - 03:35 UT, September 25 (2003268) 12:05 - 12:15 and 18:36:54 - 18:51:14 UT. Between 18:06:15 and 18:36:54, some or all data may be lost as well. The exact amount is not known at this time. Data was also lost on September 30 (2003273), 12:16:29 - 12:28:25 UT and October 14, 2003 (2003287), 19:07 - 19:14 UT.

On December 16 (data day 2003350) at approximately 13:13 UT, the Terra spacecraft went into SAFE mode. MODIS and other instruments followed. The Terra instrument transitioned back to Science Mode on December 22, 2003. On December 24 the Cold Focal Plane Assemblies reached their operating temperature (83K), the black body calibrator was powered to 290K. The Nadir Aperture Door was opened and Earth - scene data collection commenced 03:20 PM EST, December 24, 2003.

On January 15, 2004 Terra Science Data was lost from 13:43 - 13:53 UT while fixing a Direct Broadcast problem.

A period of data loss occurred between February 18, 2004, and February 19, 2004. This was caused by a Terra Science Formatting Equipment (SFE) shut down at 10:31:57 UT on February 18. SFE - A was successfully turned back on and the Science Record enabled at 16:11:38 UT on February 19.

Data loss occurred beginning at 14:36:43 UTC on 2005/266 (September 23, 2005) when TMON 16 detected a bit failure and turned off the SSR Science Formatting Equipment (SFE - A). The FOT turned SFE - A on again at 19:46:37 UTC.

Terra science pointing accuracy was degraded on June 21, 2006 (day 172) between 14:17:30 and 20:37:34 UT.

On 2006/231 (August 19, 2006) there was a non - recoverable data loss from 16:25:18 to 16:29:18 and 17:20:04 to 17:30:17 UT due to an operations error.

On 2006/234, both the Terra Nadir Aperture and Spaceview doors were inadvertently commanded closed at 234/16:37 UT.  The LWIR and SMIR focal plane assembly temperatures rose well into their yellow limits.  Science data was lost from 234/16:37 to 234/19:14, and IR data is not trustworthy until about 235/19:20.

Data on 2006300 (October 27, 2006) between 02:16 and 02:40 UT was lost when the MODIS data buffers filled before the next available science playback opportunity.

A TDRS spacecraft emergency led to inability to acquire a MODIS Science Data dump. The resulting unrecoverable MODIS data loss covers 2007/032 (Feb. 1, 2007) 19:43:13-20:46:27 UT.

TDRSS was unavailable to transmit science data and the ground antenna backup failed resulting in a data loss on day 2007079 (March 20, 2007) from
00:46:18 to 01:47:30 UT.

On DOY 2007/109 Terra experienced a failure.  To correct this failure the Flight Operations Team needed to stop science data collection to the Solid State Recorder (SSR) from 22:49:56 - 23:02:05 UT resulting in unrecoverable loss of MODIS data for that time period. Other non-recoverable data losses occurred on 2007/113 from 19:52:22 - 20:01:23, 2007/113 from 21:48:29 - 22:03:35, and 2007/117 from 15:18:31 - 15:34:24 UT.

An unrecoverable data loss occurred on 2007/158 (June 7) between 10:38:35 and 16:18:53 UT and on 2007/162 (June 11) from 16:26:15 to 17:13:40 UT.

An unrecoverable data loss due to a Science Formatting Equipment anomaly occurred on 2007/319 (Nov. 15) 18:13:52 UTC and lasted until 2007/320 (Nov. 16) 01:10:33 UTC.

An unrecoverable data loss due to a Science Formatting Equipment anomaly occurred on 2007/347 (12/13/07, 13:11:17 UTC) and lasted until 2007/347 20:30:11 UTC.


Additional smaller data losses are described and tabulated on password protected links at the site

http://jupiter02.gsfc.nasa.gov/links/links.htm


Areas where caution must still be exercised in the use of the current Level 1B product are:

  • Incomplete knowledge of sensor cross - track response
  • Electronic cross - talk in Bands 5 to 7 and 20 to 26
  • (the severity of this effect has been reduced in this release compared to previous releases)
  • Non - uniform digital count bin - fill factors (bin - width)
  • Non - uniform channel to channel response within a band (cross - track striping)
  • Band 21, a fire band, uses fixed linear coefficients calibrated from the on - board calibrator (OBC) blackbody up to 315K
  • Band 21 (detector 1, product order) and Band 24 (detector 1, product order) striping

Signal - to - noise - ratios (SNRs) for the reflected solar radiation bands (RSB; Bands 1 to 19 and 26) and noise - equivalent temperature intervals (NEdTs) for the thermal infrared bands (TEB; Bands 20 - 25, and 27 - 36) are meeting specifications in most instances.

Summary of Key MODIS Operational Configurations
Consistent operational configurations existed from November 1, 2000 to June 15, 2001. The data are aligned by rows within each calendar month from February 2000. The first row indicates whether science data is present in the Level 1 product for that day. Row two represents the value of the focal plane bias for the SW/MWIR for the preponderance of each day. Row three indicates whether the cooled focal planes were held at the nominal operating temperature of 83 K for the entire period of the day, whether they were uncontrolled over a portion of each orbit on that day and whether they were uncontrolled throughout the entire day. Row four indicates whether A - side or B - side electronics are being used for that day.

Additional MODIS Operational Configurations
This link provides Terra MODIS operational configurations in time - ordered tabular form for the following operations: Vdet value, Earth - view sector state, software version number, blackbody temperature setting, and focal plane assembly temperature control. The column labeled "other" lists blackbody duty cycle, ECAL operations, gain changes, formatter changes, electronics side, spacecraft maneuvers, significant data loss periods, and cooler outgas times. The Terra MODIS Itwk Vdet history and calibration activities are available at MODIS Instrument Operations Team Event History.

Prominent performance factors that complicated achieving optimum performance of the MODIS instrument are listed below. For a description of these effects, the projected impact on the L1B and L2 science, the instrument characteristic causing the effect, and the current mitigation strategy, access the following MCSTweb links. Areas of known concern with higher - level data products are described on the web at http://daac.gsfc.nasa.gov/MODIS/modis_disclaimers.shtml.

Responsible Civil Servant: 
Dr. Jack Xiong <Xiaoxiong.Xiong.1@gsfc.nasa.gov>

Email mcst-webm@ssaihq.com to report any problem with the MCST Web Pages.

Last Update:  Friday, December 8, 2006 3:00 PM

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