NASA said it was investigating technical problems with two instruments aboard the most powerful spacecraft ever flown to Mars.
The problems on the Mars Reconnaissance Orbiter first arose in late 2006, but they worsened this year to the point where engineers have stowed away one of the instruments.
In November, scientists operating the probe's High Resolution Imaging Science Experiment camera noticed that the image pixels were of poor quality. Although the problem had minimal impact on the crisp images beamed back so far, scientists fear the problem could grow worse.
A problem also developed in an instrument that maps the temperature, ice clouds and dust in the Martian atmosphere. Scientists discovered the instrument, called a climate sounder, had a skewed field of view. The errors became more frequent last month and engineers decided to temporarily halt work with the instrument.
The Reconnaissance Orbiter entered orbit round the Red Planet last year.
Since November, the probe has sent back data that could fill nearly 1,000 CD-ROMS, tying the record of the Mars Global Surveyor between 1997 and 2006. The Global Surveyor, which suddenly fell silent last year after a decade of work, is presumed dead.
The Reconnaissance Orbiter has pointed its eagle-eyed camera to image NASA's twin rovers on the surface and landing sites of the Viking landers and Pathfinder probe, reports AP.
The Reconnaissance Orbiter, built by Lockheed Martin, is managed by NASA's Jet Propulsion Laboratory.
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