Stardust-NEXT Mission Status Report
October 29, 2007
STARDUST was completing the camera decontamination process last week
when it went into safemode while taking images. A message que
overflowed, stopping the image sequence and the spacecraft responded
by going into safe mode. There was no computer reboot or side swap
since this was a minor error.
There is an existing software patch that increases this message que
memory space by an order of magnitude. However this patch had been
overridden by the on-board hard coded que allocation that became the
default after the safemode entry earlier this year. The intent was
to uplink this patch again to override the current default and
increase this message que memory space by an order of magnitude
prior to performing serious imaging (10's of images). The short
decontamination imaging sequence just implemented was run through
the spacecraft testlab without the patch and worked just fine. The
first implementation of this short imaging sequence prior to the
camera heating work as well during the spacecraft testlab
testing. However, mid-way through the repeat of this small imaging
sequence, after the camera heating/cleanup, the message que became
full and the spacecraft went into same mode.
Immediately after safe mode entry last week, communications were
re-established with the spacecraft and fault history was downlinked
along with other error and engineering data, leading to the root
cause of the safe mode entry to be identified. Since this safe mode
entry occurred, the spacecraft has been taken out of safe mode and
placed back into normal cruise operations with the background
sequence for the next month uplinked and post-cleanup image
telemetry initiated.
The good news is that the root cause was identified and the needed
patch already exists and will go up during the next Deep Space Network (DSN)
communication
session. The post-cleanup images that have come down show that the
camera cleanup worked extremely well, with very crisp star images as
compared to very blurred images of the same stars before camera
cleanup.
The Stardust-NExT (New Exploration of Tempel 1) mission is to flyby
the comet Tempel 1 on February 14, 2011 in order to obtain high
resolution images of the coma and nucleus, as well as measurements
of the composition, size distribution, and flux of dust emitted into
the coma. We have developed a reliable plan to update knowledge of
the rotational phase of the comet sufficiently well to have a high
probability of viewing significant portions of the hemisphere
studied by Deep Impact (DI) in 2005 and a high probability of
imaging the crater made by its impactor. The impact event produced
so much ejecta that DI did not succeed in imaging the crater.
