Mars rover Spirit misses communication session

[April 20, 2010]  LOS ANGELES (AP) -- The aging, sand-trapped Mars rover Spirit failed to make a scheduled communication this week and may have gone into a power-saving hibernation to survive the Red Planet's winter, NASA's Jet Propulsion Laboratory said Wednesday.

Spirit had been expected to communicate with the orbiting Mars Odyssey spacecraft on Tuesday.

"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," Mars rovers project manager John Callas said in a statement.

Operating on Mars since 2004, Spirit survived previous winters by positioning itself with its solar panels tilted toward the sun. But it has been stuck in sand for nearly a full Earth year, and with two of its six wheels not working, NASA decided in January to leave it be and use it for stationary science.

The amount of sunlight falling on its dusty solar panels is now declining.

Callas said that recent downlinks from the rover had shown the battery's charge was decreasing.

Hibernation mode suspends communications and other activities so energy can go to heating and battery recharging. The rover is designed to try to wake up when there is enough charge and to communicate on schedule.

"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," Callas said.

NASA noted, however, that in coming weeks Spirit's core electronics will become colder than they ever have since the rover landed in January 2004.

Temperatures should not be lower than the electronics were designed to withstand "but the age of the rover adds to the uncertainty of survival," NASA said.

Spirit and its twin, Opportunity, were launched separately from Earth in 2003 and landed on opposite sides of Mars in January 2004 for what were anticipated to be three-month missions. Instead, they have lasted years. Opportunity continues to rove.

[Associated Press; By JOHN ANTCZAK]

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