Status Report

Stardust Status Report October 5, 2001

By SpaceRef Editor
October 5, 2001
Filed under , ,

There were two Deep Space Network (DSN) tracking passes in the past
week and all subsystems are performing normally.

Data sent back from the spacecraft showed that the large solar flare last
week caused forty-four star camera outages of up to 25 seconds, compared to
only one or two normal outages per week of less than 5 seconds. The
on-board fault protection is designed to handle an outage of up to five
minutes.

Stardust is currently at 2.35 AU from the Sun, the furthest any
solar-powered spacecraft has flown. Next April, Stardust will be 2.72 AU
from the Sun and the power subsystem was designed to have margin at this
distance. The battery operating points of maximum state of charge and
state (SOC) of charge level to trigger recharge were increased for the
upcoming deep space operations. The pre-launch battery design value was 34
volts at full charge while we are now operating at about 32 volts, still
providing margin at this large distance from the Sun.

Previously, when the battery SOC reached 100%, the battery was allowed to
discharge until the SOC reached 95%. At 95% SOC the battery was then
commanded to re-charge back to 100% using a trickle charge (0.125
amps). This 5% discharge helps keep the battery cells active and in good
condition during normal cruise. The operating points of the battery were
changed to provide additional capacity and voltage by increasing the upper
SOC limit to 108%. The battery now cycles between 108% and 107%. The
battery voltage increased to 32.1 volts and the SOC was at 107.3% by the
end of the DSN pass. It is anticipated the average battery voltage will be
32 volts, providing additional power. The small depth of discharge is not
a concern, as the battery will be heavily used to provide power during DSN
passes for the next year. Next April when Stardust is at maximum distance
from the Sun, the maximum communication time is expected to be just over
two hours and will leave the battery SOC at 60%, keeping the battery cells
alive and in good condition. On-board fault protection is design to take
action only if the SOC reaches 50%.

There was an excellent collaboration between Stardust and Deep Space 1 as
it successfully flew by the Comet Borrelly. Stardust shares the optical
navigator and flight software being used aboard both spacecraft to track
the comet nucleus during flyby. This worked exceptionally well, as the
exciting images returned by DS1 showed. Also, Stardust’s project scientist,
responsible for computing the cometary dust environment and nucleus
brightness for choosing camera exposure times, performed these functions
for Borrelly, supporting the DS1 science and navigation team. Stardust has
gained valuable flight experience from this collaboration and is now better
prepared for its Comet Wild 2 encounter in 2004.

For more information on the Stardust mission — the first ever
comet sample return mission — please visit the Stardust home page:

http://stardust.jpl.nasa.gov

SpaceRef staff editor.