Mission Status 2010
Tim Larson Stardust Spacecraft Team
December 15, 2010
The spacecraft experience another safe mode entry on Thursday, December 9. The next communications pass was scheduled for Friday morning, and the team was able to establish communications quickly with the help of the DSN personnel, and a health check revealed all the subsystems were healthy and operating normally. The playback of all available data – command history logs, error logs, lower DRAM dump, etc. – was started. Safe mode entry was completed on Saturday, December 11, getting the spacecraft back under the control of the background sequence, easing communications during the planned DSN tracks. The data showed that this safe mode entry was caused by a MEEB (Memory Error External Bus) event. This a phenomenon observed on other spacecraft using this processor and memory architecture. It is caused by a latch-up of a redundant memory address register that causes the memory checking software to check a region of memory never used before and encountering many uncorrectable errors due to this. In response, the system is rebooted, and the reboot process then checks and corrects these new memory addresses and the system continues operating. The analyses performed on other missions have concluded that the standard response to a MEEB is a cold boot that resets the memory address registers to the original values. A tiger team was convened to help the project address this latest event in light of the two other recent safe mode entries. The tiger team has concluded its work and concurs with the project plan to perform a cold boot on side B to prepare the spacecraft for the upcoming comet flyby. This reboot is currently planned for January 4, 2011. Until then, the spacecraft will be acquiring optical navigation image sets twice a week.
December 8, 2010
The spacecraft is now about one week away from initiating its optical navigation imaging of comet Tempel 1. These first OpNav images, to be acquired on December 16 will be the first images of the comet from the spacecraft. The spacecraft will acquire 2 optical navigation image sets per week until January 4, when it will then begin the daily science imaging campaign. The Critical Events Readiness Review was held on December 8 with very helpful feedback from the board.
December 1, 2010
The spacecraft continues in cruise mode. The team continues to prepare for encounter by testing the sequences to be used. The project will hold a Critical Events Readiness Review on December 8.
November 17, 2010
The spacecraft is back in cruise mode after recovering from another safe mode event last week. On Thursday, November 11, the spacecraft entered safe mode due to an IMU data point fault. This was discovered during the pass scheduled for November 13. The spacecraft had power cycled the IMU, which cleared the fault, and entered safe mode to await further instructions. When the subsystems were determined to all be healthy, all the command and error logs were downlinked, and the spacecraft was commanded out of safe mode. The investigation into the cause of this data point error is ongoing. Along with this investigation, the team continues to prepare for the upcoming TCM 30A on November 20, and continues finalizing the design of the flyby sequences. These sequences are undergoing tests, testing nominal cases and faulted cases testing the autorecovery capability.