NASA's Mars Exploration Rover Opportunity sent signals Monday morning, July 23, indicating its power situation improved slightly during the days when it obeyed commands to refrain from communicating with Earth in order to conserve power.

Dust storms on Mars in recent weeks have darkened skies over both Opportunity and its twin, Spirit. The rovers rely on electricity that their solar panels generate from sunlight. By last week, output from Opportunity's solar panels had dropped by about 80 percent from a month earlier.

Rover controllers at NASA's Jet Propulsion Laboratory, Pasadena, Calif., commanded Opportunity last week to go into a very low-power state and to communicate only once every three days. The rover transmitted a small amount of information today. Next scheduled transmission will be Thursday, July 26, though controllers may command Opportunity to send information on Tuesday, July 24.

Meanwhile, communications from Spirit over the weekend indicated that the sky had cleared slightly at Spirit's location on the other side of Mars from Opportunity.

"The outlook for both Opportunity and Spirit depends on the weather, which makes it unpredictable," said JPL's John Callas, project manager for both rovers. "If the weather holds where it is now or gets better, the rovers will be OK. If it gets worse, the situation becomes more complex.

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