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Daily Updates - June 2, 2004
Spirit Status at end of sol 136 - 139

Spirit had plans to spend sols 136 through 139 observing its surroundings with the remote sensing instruments on its mast, and then exploring the trench it dug on sol 135 with the instruments on the robotic arm. However, an anomaly on sol 136 restricted the rover's activity, allowing Spirit to achieve only remote science objectives during the four-sol segment. Spirit has since fully recovered and has resumed normal science operations. On sol 136, engineers sent Spirit its commands and received the beep confirming that they were running. However, the afternoon pass by NASA’s Mars Odyssey orbiter did not provide any data, and the orbiter reported that it had not heard from Spirit's UHF antenna. Engineers first thought was that the signal might have been blocked by the "Columbia Hills" because of the low elevation pass of Odyssey. The telecommunications team disagreed with this hypothesis and thought something might be wrong. Scientists and engineers would have to wait until the afternoon of sol 137 for their next communications opportunity.

During sols 136 and 137, engineers executed a number of communication trials with Spirit, but did not receive any telemetry from the rover, or have any indication of what had gone wrong until finally data came back from a sol 137 afternoon pass by NASA’s Mars Global Surveyor. That pass revealed that on sol 136, Spirit's software had experienced an extremely low probability error that rebooted the computer and terminated all the sequences. This error created a domino effect of communication difficulties and explained why engineers had not been able to make contact with the rover. All the anomaly events are understood.

Sol 138 was spent recovering the state of the rover, including reestablishing a master sequence, restoring high-gain antenna communications, and reinitializing the panoramic camera mast actuators whose positions had been marked as unknown.

On sol 139, Spirit performed the remote-sensing observations that had been lost along with some observations coordinated with Mars Global Surveyor that had been planned for sol 138. All activities on sol 139 completed successfully, which verified that Spirit had returned to normal science operations.

Engineers have developed a way to reduce even further the probability of encountering this particular error again and reported that on the bright side, Spirit was able to fully charge its batteries during the anomaly.

Sol 140 picked up with the original plan for Sol 137, performing in-situ work in the trench.

Spirit Daily Update Archive