MODIS IOT Terra Weekly Report

Mission Operations Days: 1999/360 to 2000/002
December 25, 1999 15:00:00 EST to January 2, 2000 14:59:59 EST

Terra Spacecraft and MODIS Instrument Status:

This Week's Completed MODIS Activities:

None

None

None

None

None

None

None

None

This Week's Scheduled MODIS Activities Not Completed:

None

Upcoming MODIS Events:

01/03/2000: MODIS Turn on and transition to Standby Mode
01/03/2000: Unlatch Space View Door, move to Outgas position
01/03/2000: Turn on Outgas heaters

01/04/2000: Unlatch the Solar Diffuser Door
01/04/2000: Unlatch the Nadir Aperture Door

MODIS Anomalies:

None

General Instrument Comments:

MODIS is in a nominal Survival Mode and is a bit colder than expected with temperatures in the range of -9 to -20 degrees Celsius. The MEM survival heater is activating regularly with an approximate duty cycle of 75%. Due to these colder temperatures, next week's scheduled turn on activities have been changed from using the primary side electronics to using the redundant side.

MODIS Telemetry Trends:

The optical bench bulkhead temperature is experiencing oscillations based on the spacecraft day to night cycle. The two main electronics module temperatures as well as the FAM and KM1 temperatures are varying with the MEM survival heater cycle. The remaining three temperature sensors have reached steady-state values.

Non-MODIS Significant Events:

MODIS is in a nominal Survival Mode.

This following was accomplished to recover the Spacecraft from Safe Hold:

• SCC1 back to operational
• Appropriate TMONs re-enabled
• YGC pointing
• Acquire data using the HGA

Analysis indicates that the Motor Drive Assembly (MDA) BITE 2 flag anomaly was caused by a single event upset while the spacecraft was traversing the SAA. A telemetry monitor (TMON) has been developed that will reset the MDA if a BITE 2 flag is set only once within 3,000 seconds. The following is a summary of the MDA2BITE failures to date:

Analysis of the SCC 1 dump indicates that the computer went into Safe Mode after the navigation background process attempted to resolve the arcsine of a number less than -1 while calculating a solar ephemeris. This calculation occurred at the time of the Winter Solstice (356/07:43 GMT) when the right ascension of the sun was at 270 degrees. It was also determined that Lunar ephemeris computations using the same arcsine function will cause the SCC to halt when the moon's right ascension is 90 and 270 degrees.

No notable problems arose throughout the entire Y2K transition.

We are on the schedule as listed above, however the S/C has some procedures they have to complete before we have our turn. Assuming all goes well, we should be actively outgassing by the end of the day. Bill Merriman will be here with us Monday morning for the day's events.

Limited Life Item Status:

This summary will be deferred until next week's report.

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Last Update: Thursday, 27-Feb-2003 13:44:29 EST