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October 29, 1997

Mars Pathfinder's operations team is continuing daily efforts to reestablish communications with the lander. Over the last month the team has been working through all credible problem scenarios and taking a variety of actions to try to recover the link with Pathfinder. They plan to continue sending commands to the spacecraft for another week before shifting to a contingency plan of less frequent commanding and listening.

During the past month, the team has investigated a variety of scenarios that could explain why the Pathfinder lander has not sent telemetry to Earth since September 27. Since that time, ground stations have detected a carrier signal from the lander on two occasions, but on each attempt following the receipt of the carrier signals they were not able to reestablish a link, and therefore no digital data was received to enable determination of the spacecraft's condition.

The team initially investigated the possibility that the lander's battery had failed. This scenario would have resulted in spacecraft clock uncertainties and unknown spacecraft power conditions due to the lander only operating on solar power. They then investigated the possibility that, because the lander's transmitter had been turned off for many days, the lander's temperature had dropped to a range between -50 and -30 C (-58 to -22 F), some 20 to 40 degrees C (about 35 to 70 degrees F) colder than previous operating temperatures, causing its radio receiver to shift away from its normal frequency range.

Currently the team is sending commands to the lander to investigate the possibility that the spacecraft's flight computer is not operating normally. "Under this scenario, the thought is that perhaps the computer is not booting up fully," said Mission Manager Richard Cook. "The team is sending resets to the lander at various times of the day before we attempt to send other commands."

All scenarios are expected to have been fully investigated by end of day on Tuesday, November 4. If the team does not reestablish contact by then, said Project Manager Brian Muirhead, they plan on shifting to a contingency strategy of sending commands to the lander only periodically, perhaps once a week or once per month. "The normal extended mission would be over, but there is still a small chance of reestablishing a link, so we'll keep trying at a very low level," Muirhead said. "Of course the science team will continue to process, catalog and understand the large volume of science data we have received, which will keep us very busy for several months."

Although the true cause of the loss of lander communications may never be known, recent events are consistent with predictions made at the beginning of the extended mission in early August. When asked about the life expectancy of the lander, project team members predicted that the first thing that would fail on the lander would be the battery; this apparently happened after the last successful transmission September 27. After that, the lander would begin getting colder at night and go through much deeper day-night thermal cycles. Eventually, the cold or the cycling would probably render the lander inoperable. According to Muirhead, it appears that this sequence of events may have taken place. The health and status of the rover is also unknown, but since initiating its onboard backup operations plan three weeks ago, it is probably in the vicinity of the lander attempting to communication with the lander.

At the time the last telemetry from the spacecraft was received, Pathfinder's lander had operated nearly three times its design lifetime of 30 days, and the Sojourner rover operated 12 times its design lifetime of seven days. Since its landing on July 4, 1997, Mars Pathfinder has returned 2.6 billion bits of information, including more than 16,000 images from the lander and 550 from the rover, as well as more than 15 chemical analyses of rocks and extensive data on winds and other weather factors. The only remaining objective was to complete the high-resolution 360- degree image of the landing site called the "Super Pan," of which 83 percent has already been received and is being processed.

Daily audio updates on Mars Pathfinder's status are available by calling (800) 391-6654.