Status 12 January 2000, 10:45 AM PST
About 1 minute into yesterday afternoon's firing of the Terra propulsion
system, telemetry from the GN&C (guidance, navigation, and control)
subsystem detected an excessive rate of change of spacecraft roll and the
burn was shut down. The spacecraft went into "safe" mode, which prompted
all the instruments to follow suit. MISR's computer automatically commanded
the cameras to turn off, and the set point for optical bench temperature
control was lowered to 5 degrees Centigrade. The optical bench cooled to 10
degrees C within about 8 hours of the safing event. It is currently at
about 6 degrees C.
No explanation for the excessive roll rate has been provided as yet, but a
team to investigate the anomaly has been formed. At this time, the
spacecraft remains in safe mode, and is stable. Unlike the safe condition
that occurred as a result of the December "solstice bug", the spacecraft
controls computer (SCC) is fully operational (though a different processor
is in charge right now); therefore an "IMOK" ("I'm OK") signal from the
spacecraft is being received by MISR, and telemetry monitors are activated.
In light of this, and in order to maintain the bake-out benefit of keeping
the instrument warm, MISR was taken out of safe this morning and the
cameras and heaters were once again turned on. All looks fine.
A re-try of the ascent burn is now scheduled for no earlier than January
19. Loading of MISR flight software and opening of the cover are
consequently delayed by at least a week.
You can see earlier status reports by checking the "News" link of the MISR
web site at http://www-misr.jpl.nasa.gov.
David Diner
Return to top
Return to 2000 Index.
Return to News section.
|
