Spirit May Have Begun Months-Long Hibernation

[Wilms]

Spirit May Have Begun Months-Long Hibernation

Monday, April 5, 2010

MARS EXPLORATION ROVER MISSION STATUS REPORT

PASADENA, Calif. -- NASA's Mars Exploration Rover Spirit skipped a planned communication session on March 30 and, as anticipated from recent power-supply projections, has probably entered a low-power hibernation mode.

In this mode, the rover's clock keeps running, but communications and other activities are suspended in order to put all available energy into heating and battery recharging. When the battery charge is adequate, the rover attempts to wake up and communicate on a schedule it knows.

"We may not hear from Spirit again for weeks or months, but we will be listening at every opportunity, and our expectation is that Spirit will resume communications when the batteries are sufficiently charged," said John Callas of NASA's Jet Propulsion Laboratory, Pasadena, Calif., who is project manager for Spirit and its twin rover, Opportunity.

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"We are checking other less-likely possibilities for the missed communication, but this probably means that Spirit tripped a low-power fault sometime between the last downlink on March 22 and yesterday," Callas said. "The recent downlinks had indicated that the battery state of charge was decreasing, getting close to the level that would put Spirit into this hibernation."

In coming weeks, Spirit's core electronics will become colder than any temperature they have ever experienced on Mars. Thermal projections indicate the temperature probably will not drop lower than the electronics were designed and tested to tolerate, but the age of the rover adds to the uncertainty of survival.

"The temperature limit was for a new rover. We now have an older rover with thousands of thermal cycles on Mars, so the colder temperatures will be a further stress," Callas said.

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http://www.nasa.gov/mission_pages/mer/news/mer20100331.html