NASA's hobbled Mars rover Spirit has made its last short drives of the season and is now parked for the Martian winter, which mission managers hope it will survive.
Spirit got stuck in a sand trap on Mars last April and NASA officials announced last month that they were putting a halt on the efforts to free the long-lived rover. Instead, NASA started a new mission for Spirit, one that will use the six-wheeled robot as a stationary science outpost.
The change for Spirit came after more than six years spent roaming the Martian surface. Spirit landed on Mars in January 2004 a few weeks ahead of its twin Opportunity, which is working fine and roving to a giant crater on the other side of Mars.
The rover team is commanding Spirit this week to make additional preparations for the Mars southern hemisphere winter season and doesn't plan to tell the rover to move its wheels again until spring.
"We have hope that Spirit will survive this cold, dark winter that we have ahead of us and be ready to do more science come springtime," said Steven Squyres, the rover mission's principal investigator at Cornell University in Ithaca, New York, when NASA announced Spirit's stationary plan on Jan. 26.
Stuck on Mars
Spirit's last drive before winter took place on Feb. 8, when the rover changed the angle of its suspension system, but it did not produce a hoped-for improvement to the overall tilt of the solar array for catching winter sunshine.
The last set of drives, taken since Jan. 15, have move Spirit 13 inches (34 cm) to the south-southeast.
But the rover hasn't been able to maximize its tilt to catch as much of the low winter sun's rays as possible during and is left in a position tilted 9 degrees to the south. Spirit's parking positions for its previous three Martian winters tilted northward.
Engineers anticipate that, due to the unfavorable tilt for its fourth Martian winter, Spirit will be out of communication with Earth for several months.
Spirit may enter a low-power hibernation mode within a few weeks, shutting down almost all functions.
The rover is expected to keep its master clock running and check its power status periodically until it has enough power to reawaken. It may go in and out of this mode a few times at the beginning and at the end of an extended hibernation period.
This week the rover team is uploading schedules to Spirit for when to communicate with Earth or with the orbiting Mars Odyssey during the rest of this year and into 2011. Spirit will use these schedules whenever it has adequate power to wake up.
Spirit will take a set of "before" images of surroundings from the parked position this week, for comparison with images in the Martian spring to study effects of wind.
Images toward the south will also aid preparations for possible future drives, although, with only four of its six wheels still working, the rover is not expected to move farther than short repositioning drives.
Other preparations for winter will include putting the robotic arm into a position for studies of atmospheric composition when power is available and changing the stow positions of the high-gain antenna and panoramic camera to minimize shadowing of the solar panels.
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