Mars Exploration Rover Update - April 9, 2004

http://marsrovers.jpl.nasa.gov/mission/status.html

SPIRIT UPDATE: Spirit Stands Down for Flight Software Update -
sol 94, Apr 09, 2004

Spirit began a four-sol stand-down on sol 94, which ended at
8:37 p.m. on April 8, 2004. During this time, the rover will
receive a flight software update that should make its
remaining martian days even safer and more productive. The
upload will run through sol 97 with a rover re-boot on sol 98,
Monday, April 12. Opportunity will be receiving the same
update package in upcoming sols.

Spirit is currently parked in front of the rock called
"Route 66," and will remain there for the duration of the
flight software update, with the Mössbauer spectrometer
integrating on the rock, and the alpha particle X-ray
spectrometer pointed up to the sky.

The flight software update package includes three key changes.
First is an update to the autonomous navigation software that
will allow Spirit to travel longer distances autonomously
over the extremely rocky Gusev Crater terrain. The current
autonomous navigation software sometimes gets stuck when it
detects a hazard that it can't navigate around. The new
version will allow Spirit to turn in place to find the best
possible path.

The second part of the flight software update will allow
Spirit to recover more easily from an anomaly like the
one that occurred on sol 18. Although operational processes
and software have already been updated to prevent something
like this from ever happening again, engineers have included
additional safety nets in the software that would allow the
rover to autonomously react to a similar anomaly and recover
to a more stable state.

The third portion of the update is specific to Opportunity
and is intended to mitigate against energy loss associated
with the stuck heater on Opportunity's instrument deployment
device. The fix allows rover planners to put the rover in a
deep sleep mode, where the batteries are totally removed
from being able to power the stuck switch. Therefore, with
no power reaching the stuck heater switch, the Opportunity
rover battery will not be drained. Rover controllers will
not initiate the deep sleep capability on Spirit unless it
becomes necessary.