Terra Mission Status Update

Status Update Archive

June 22 - 28, 2007

Terra spacecraft and instrument subsystems are in nominal operations.

Terra successfully performed Risk Mitigation Maneuver on 6/22/07 with burn duration of 1.352 seconds. A week of tracking and analysis predicted a piece of Fengyun 1C debris with estimated probability of collision 7/100 (6.746e-2) prior to burn. Terra's thruster pulse 24 hours preceding the conjunction allowed 1.3 kilometers of separation to accumulate and reduce the risk to zero. Terra's predicted seven day orbital path is routinely screened by the Air Force for potential conjunctions with space debris based on their catalog and its updates. The findings are then reprocessed and analyzed by ESMO engineers to assess the probability of collision. The predictions have a fair amount of inaccuracy at the minus 7 day prediction limit, this improves both with time and with multiple screenings from multiple sites. Terra routinely conducts orbit maintenance to compensate for atmospheric drag. Terra has the option to conduct a small drag make up maneuver ahead of schedule if analysis shows a high probability of collision if Terra remains on its present path. The entire conjunction assessment and collision avoidance process is a new and maturing.

A NAV slot change from TDRS East (TDE) to TDRS 275 for TONS (TDRSS Onboard Navigation System) was successfully completed on 6/27/07. Terra flight operations had switched to TDE prior to Shuttle mission to increase playback opportunities. Switched back to 275 for better TONS performance and reduce zone of exclusion.

Investigation continues into the Terra spacecraft Ultra Stable Oscillator clock error jump from -23 to -50 microseconds offset on May 31st, 2007. The clock has always drifted and a correction factor is routinely periodically computed and uplinked. This step change is new and due to unknown cause.

Terra is planning a -11.13 degree MODIS Roll Maneuver on 7/4/07.

The Terra ASTER SWIR Cryocooler completed a fifth week back at the 6mm compressor stroke length. The detector temperature continues to rise at the typical slope. Using this drift rate, the detector temp max will reach 83K on 6/30/07 and the detector temp average will reach 83K on 7/8/07 at which point the first science impact begins on bright scenes. An array of amplifier gain/offset adjustments are being considered for use in the coming 6 months. The Japanese instrument team is assessing the cost and schedule to modify existing algorithms to adjust for the degradation and eventual loss of the SWIR band.