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 Mossbauer 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 M�ssbauer spectrometer.
During sols 256 through 257, Spirit took 48 more hours of Mossbauer observations on the filter magnet. A dirt clod from a previous Mossbauer 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 Mossbauer data on the uncontaminated dust sample from that magnet. This is because when the M�ssbauer 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 Mossbauer 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 M�ssbauer spectrometer was removed clearly showed dirt still attached to the M�ssbauer 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 M�ssbauer 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 Mossbauer 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 M�ssbauer 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 Mossbauer 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.