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Mission Status 2007
Kevin V. Gilliland Stardust Spacecraft Team

November 14, 2007
On Thursday, November 8, the remainders of the post-bake NAVCAM images were received on the ground. The de-fragmentation of the memory, reducing the memory free list, was performed during the tracking pass on Friday, November 9.  All subsystems are nominal as Stardust continues its quiescent cruise. As part of the on-going task of improving attitude control performance to reduce fuel consumption, a revised dead-band controller was installed during the Friday track.  Early analyses show an approximate 20% reduction in thruster firings. This trend will continue to be monitored to verify the initial improvement. The commands for the background sequence SN005 will be sent to the spacecraft later this week.

November 7, 2007
On Thursday, November 1, the spacecraft entered safe mode for the second time in a week. As before, communications were quickly re-established and no reboots or side swaps had occurred.  Safe mode was requested by the sequencing software when it issued a command to turn off the NAVCAM Mirror and received no response to that request.  The root cause was an overflow of the NAVCAM software task message queue that prevented the proper response to the command.  On Friday the spacecraft successfully exited safe mode.  All subsystems are nominal as Stardust continues its quiescent cruise. This safe mode entry is similar to the October 25 entry in that commands were being issued to return the camera and mirror to their stowed position. A common factor between the two safe modes is the length of the Heap Free list. The Free list is a measure of the memory fragmentation and a long list means the time to find space for telemetry packets increases. The combination of a long free list, a small message queue size and a low task priority for the NAVCAM software contributed to the request for safe mode.  The de-fragmentation of the memory, ensuring the free list is small, will be performed prior to any future actions with the NAVCAM. The software patch to increase the message queue size was installed during the tracking pass on Monday, November 5. The commands for part two of the background sequence SN004 was sent to the spacecraft during the pass on Friday.

November 1, 2007
On Thursday, November 1, during the NAVCAM commanding, the spacecraft entered safe mode.  Signal was lost at approximately 2007-305/21:04.  Communications were quickly re-established following a command to return to Earth.  Signal was acquired at approximately 2007-305/23:12. We determined that no reboots or side swaps had occurred, and that  Safemode was requested by the sequencing software when it issued a command to turn off the NAVCAM power.  Today's events are very similar to the NAVCAM task overflow seen last week. At this time, data is being collected to determine the root cause. The spacecraft is stable and all subsystems are nominal. Tomorrow's (Friday, November 2) passes will be used to continue to collect data, and recover from the Safemode entry.

October 31, 2007
On Thursday, October 25, during the NAVCAM post “bake” imaging the spacecraft entered safe mode.  Communications were quickly re-established and we determined that no reboots or side swaps had occurred. Safe mode was requested by the sequencing software when it issued a command to turn on the NAVCAM calibration lamp and received no response.  The root cause was an overflow of the NAVCAM software task message queue that prevented the proper response to the command.  On Friday the spacecraft successfully exited safe mode.  All subsystem’s are nominal as Stardust continues its quiescent cruise. The first two images were down-linked during the Friday track and they showed significant improvement in the image clarity. An additional two images will be sent during the upcoming scheduled contacts.  There is an existing software patch that increases the size of the message queue but it was not re-installed after the reboot in February 2007 during the re-contact effort. That patch will be installed during the track on Thursday, November 1. An on-going task has been to review spacecraft parameters and subsystem performance to see if any improvements in the attitude control can be achieved to reduce fuel consumption.  Several possibilities have been identified and are being examined.  One of those ideas, increasing the RCS catbed temperature operating limits, will be sent to the spacecraft on Thursday, November 1. Raising these set-points should increase the thruster efficiency by providing an increase in thrust for each 15 ms pulse that is commanded for attitude dead-band control.  This improvement is possible because the solar distance for the Stardust-NExT mission is 1.6 AU that means we have sufficient power. The commands for part two of the background sequence SN004 are in the final review process and will be sent to the spacecraft next week.

October 17, 2007
All subsystem’s are nominal as Stardust continues its quiescent cruise.   
Last Friday, October 12, commands were sent to take images using the Navigation Camera (NAVCAM) in preparations for the de-contamination (“bake” maneuver) on October 18. Due to the low data rates approximately one half of the first image has been received on the ground.  Early analysis shows the expected contamination is present. The NAVCAM CCD heater was turned on and its temperature reached its steady state value of 12.3°C.  The “bake” maneuver is expected to increase the CCD temperature to approximately 24°C.

October 3, 2007
Stardust is continuing its quiescent cruise and all subsystems are nominal as preparations for the Deep Space Maneuver continue. The DSM is approximately 3.5 m/s burn with the sun edge-on to the solar panels on the –Y side of the spacecraft. This burn attitude means there will be no real-time communications possible however the telemetry will be recorded and played back when communication is re-established when the spacecraft returns to its nominal earth-point attitude. The maneuver execution starts at 9 am (MDT) on Wednesday, October 10. Planning for the first de-contamination of the Navigation Camera is in development.  As was done during the Stardust mission we will rotate the spacecraft to place the sun on the bottom side in order to raise the CCD temperature to about 27°C.

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