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Spirit rover buttons down for harsh winter on Mars

Posted: February 14, 2010

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The Spirit rover will spend the upcoming Martian winter in an unfavorable orientation tilted away from the sun, limiting its power production and likely ensuring the robotic explorer will be out of contact with Earth for up to six months.

This fisheye view from Spirit's rear hazard avoidance camera was taken Feb. 8. Credit: NASA/JPL-Caltech
NASA gave up on freeing Spirit from the grasp of a Martian sand pit last month, but officials hoped spinning the robot's four operating wheels would nudge the rover's tilt angle more toward the sun.

Spirit's last drive last week failed to improve its position, and NASA says the rover will spend the winter tilted 9 degrees to the south. The sun appears low in the northern sky at Spirit's station in Gusev crater.

Ground controllers have curtailed some of Spirit's drive operations during previous winters, but the rover has always been placed in a north-facing incline to maximize its exposure to sunlight to produce electricity.

"Engineers anticipate that, due to the unfavorable tilt for this fourth winter, Spirit will be out of communication with Earth for several months," NASA said in a statement.

NASA has not lost contact with Spirit for such a lengthy period since the spacecraft landed on Mars in January 2004.

Spirit has been stuck in a sand pit dubbed Troy along the western edge of a feature called Home Plate since last April. Engineers spent much of last year developing plans to extricate the rover, but driving efforts since November have yielded little progress, partially due to the failure of a second of Spirit's six wheels.

In late January, mission managers gave up attempts to move Spirit, instead focusing on optimizing the craft's tilt angle to improve its prospects of surviving the harsh winter.

But those efforts fell short, and ground teams are now prepping Spirit for up to six months of hibernation.

Artist's concept of the Spirit rover. Credit: NASA
When Spirit's power levels fall below limits, the rover will shut down almost all of its systems except a master clock to periodically check its power status until there is enough electricity to wake up and radio Earth or an orbiting satellite, according to NASA.

Engineers are uploading a schedule of communications opportunities in 2010 and 2011 with Earth and the Odyssey spacecraft circling Mars. Controllers are also preparing Spirit's robot arm for atmospheric studies and changing the positions of high-gain antenna and panoramic camera to minimize shadows on the craft's solar panels.

Spirit is also taking a collection of images of nearby terrain. Scientists will use the pictures to compare with imagery the rover will take after waking up, providing "before" and "after" views showing the effects of wind through the winter.

NASA says Spirit could enter hibernation by early March, and the rover's power situation may not improve until September.

Spirit was built to endure the cold temperatures and low solar angles during Martian winter, but the rover has operated on Mars nearly 25 times longer than designed.

The rover parachuted to a bouncy airbag landing on Jan. 3, 2004. Spirit completed its primary mission three months later and has now survived for more than six years.

Opportunity, a twin rover of Spirit, is continuing driving on the opposite side of Mars. Opportunity is headed for the expansive 13.7-mile-wide Endeavour crater for more science investigations.