NASA Mars rover Spirit decides not to phone home

NASA Mars rover silent after recent satellite pass

It wasn't a complete surprise but NASA's long-suffering Mars river Spirit missed a scheduled call home this week, leading space agency scientists to say the spacecraft likely entered full-on winter hibernation.  

In what NASA calls low-power hibernation mode, Spirit's clock will keep running, but communications and other activities are suspended in order to put all available energy into heating and battery recharging. When the battery is charged, the rover will attempt to wake up and communicate, NASA said.

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"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 Lab in a statement.  Callas is project manager for Spirit and its twin rover, Opportunity.  

NASA said Spirit had been communicating on a once-per-week schedule in recent weeks. During the designated time for the rover to communicate with NASA's Mars Odyssey orbiter passing overhead on March 30, Odyssey heard nothing from the rover. 

NASA scientists have uploaded communications 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 communicate 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, NASA stated. 

That is if it can actually perform any of these activities. NASA said Spirit will spend the coming winter month's tilted 9 degrees toward the south, an unfavorable attitude for the solar panels to catch rays from the sun in the northern sky. Spirit's parking positions for its previous three Martian winters tilted northward. Engineers anticipate that, due to the unfavorable tilt for this fourth winter, Spirit could be out of communication with Earth for several months. 

NASA said 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. 

In January NASA said it was resigned to leaving the rover in place and making adjustments to help it survive as a remote but stationary science robot. The rover's mission could continue for several months to years. 

Spirit has been stuck in a place NASA calls "Troy" since April 23, 2009 when the rover's wheels broke through a crust on the surface that was covering brightly-toned, slippery sand underneath. After a few drive attempts to get Spirit out in the subsequent days, it began sinking deeper in the sand trap. 

Spirits twin rover Opportunity, last week got a software upgrade that will let it to let it make its own decisions about what items like rocks and interesting red planet formations to focus its cameras on. 

The new system, which NASA uploaded over the past few months, is called Autonomous Exploration for Gathering Increased Science, or AEGIS and it lets Opportunity's computer examine images that the rover takes with its wide-angle navigation camera after a drive, and recognize rocks that meet specified criteria, such as rounded shape or light color. It can then center its narrower-angle panoramic camera on the chosen target and take multiple images through color filters, NASA stated.

 AEGIS lets Opportunity look at rocks at stopping points along a single day's drive or at the end of the day's drive. This lets it identify and examine targets of interest that might otherwise be missed, NASA said.

 NASA said the first images taken by the Mars rover choosing its own target show a rock about the size of a football, tan in color and layered in texture. It appears to be one of the rocks tossed outward onto the surface when an impact dug a nearby crater. Opportunity pointed its panoramic camera at this unnamed rock after analyzing a wider-angle photo taken by the rover's navigation camera at the end of a drive on March 4. Opportunity decided that this particular rock, out of more than 50 in the navigation camera photo, best met the criteria that researchers had set for a target of interest: large and dark, NASA stated. 

The Opportunity rover is en route toward a large crater known as Endeavour. NASA scientists expect to look inside a rocky bowl 22 kilometers (13.7 miles) across. 

The rover traveled 3.3 miles in 2009, farther than in any other year on Mars, NASA stated.  Overall Opportunity has driven more than 11 miles and returned more than 133,000 images. The rover has made numerous discoveries, including the first mineralogical evidence that Mars had liquid water, according to the space agency.

Follow Michael Cooney on Twitter: nwwlayer8

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