SPIRIT UPDATE: Spirit back to normal operations - sol 243-262, September 29, 2004
Spirit has successfully transitioned back to normal operations from
conjunction operations, when Mars and Earth were on opposite sides of
the Sun. During conjunction (sols 244 through 255), engineers and
scientists did not attempt normal operations due to the low probability
of successful communications. From sols 244 to 249, the rover team did
transmit several "no operation" commands to test the communications
link. On Spirit's sol 249, Opportunity experienced an unexpected
software reset, apparently triggered by a corrupted "no operation"
command. As a result of that problem, engineers ceased all commanding on
Spirit from sol 250 until sol 256, at which time the likelihood of
receiving corrupted commands was once again very low.
From sols 244 through 255, pre-loaded sequences performed daily science,
which included atmospheric studies (using the miniature thermal emission
spectrometer and the panoramic camera) and Mössbauer spectrometer
integration on the filter magnet, which is one of two dust-collecting
magnets on Spirit's main deck. Spirit relayed data to the Mars Odyssey
orbiter every afternoon throughout conjunction. Odyssey in turn
attempted to relay that data back to Earth with limited success due to
solar conjunction. As a result of the difficulties getting data off of
the rover, the memory available for science data storage shrunk to
roughly 100 megabits by sol 261, but has recovered as of sol 262 to
roughly 400 megabits.
Sol highlights:
Sol 243 was the last sol of normal commanding for Spirit before
conjunction. The rover team successfully re-transmitted four conjunction
sequences that had not made it on-board during the sol 242 uplink. The
team saw no transmission errors (but commanded everything twice just in
case), and the rovers performed the commanded remote sensing science.
On sol 244, the rover team transitioned into conjunction operations and
did the first "no-op" commanding tests during midday to see how
effective the command link was as Mars moved further behind the Sun. The
team received data from the Odyssey orbiter indicating that Spirit was
healthy and proceeding normally with on-board conjunction sequences.
Sols 245 through 255 were the solar conjunction quiet period. No
commanding was done. Spirit automatically took daily atmospheric science
measurements and made filter magnet observations with the Mössbauer
spectrometer.
During sols 256 through 257, Spirit took 48 more hours of Mössbauer
observations on the filter magnet. A dirt clod from a previous Mössbauer
soil touch was inadvertently placed on the perimeter of the filter
magnet on sol 240. As a result, engineers believed this could have been
the rover team's last best chance to collect Mössbauer data on the
uncontaminated dust sample from that magnet. This is because when the
Mössbauer instrument was removed, there was a chance that dirt from the
clod would sprinkle or spread to the center area of the magnet.
On sol 258, the team removed the Mössbauer instrument from the filter
magnet and took microscopic images of the both magnets. From the image
thumbnails, the team could see that some dirt from the clod was indeed
deposited on the outer area of the filter magnet. Front hazard-avoidance
camera images taken after the Mössbauer spectrometer was removed clearly
showed dirt still attached to the Mössbauer contact plate.
After finishing with the magnets, engineers moved the rover arm back
down to the soil, to the same spot that had been touched by the
Mössbauer instrument on sol 240. The rover team then repeated a
microscopic imager sequence of that soil to see if winds had deposited
anything there during conjunction. The team then centered the alpha
particle X-ray spectrometer on the same soil and started an integration
later that night.
On sol 259, Spirit changed tools to the Mössbauer spectrometer and
started a 24-hour integration on the same disturbed soil spot. Spirit
also started a three-sol thermal investigation, using panoramic camera
and miniature thermal emission spectrometer observations of soil targets
several times during each sol.
On sol 260, Spirit completed the Mössbauer integration of the disturbed
soil.
On sol 261, Spirit stowed its arm then drove backwards 1.5 meters (4.9
feet) to take post-conjunction panoramic camera pictures of the soil
underneath the rover as part of the conjunction wind experiment. Spirit
also took navigation camera images of the road ahead in preparation for
future drives.
On sol 262, due to the limited amount of available science data storage,
planned activities were limited to a Mössbauer spectrometer integration
on a rock, limited remote sensing, and routine atmospheric observations.
That plan did not make it on board due to a problem during the
communications uplink session. The deep space network antenna was
pointed a few degrees below its lower safety limit when the transmitter
was supposed to turn on, causing an interlock mechanism to turn off the
transmitter. By the time the antenna was reconfigured, not enough time
remained to get the full sequence load transmitted. Fortunately, one
sequence did make it to the rover and was successfully executed, freeing
up roughly 250 megabits of memory for future sols. Sol 262 ended on
Sept. 28.
