Deep Sleep Mode Allows Mars Rover To Recharge

When the Mars rover Opportunity's instrument heater wouldn't turn itself off when it wasn't needed, NASA's Jet Propulsion Lab was faced with a tough decision: risk some of the temperature-sensitive equipment used to conduct soil tests or put the whole rover to sleep during the Martian night in order to save power. Otherwise, the heater, which was running both day and night, would drain the solar-fed power cells and render the rover almost useless.

The scientists riding shotgun on Opportunity decided to risk it. So they put the rover in "deep sleep" mode. It worked.

"Opportunity successfully executed our second deep sleep of the mission," said mission flight director Chris Lewicki in JPL's recorded update. "We survived the night just fine with that and it saved the energy that we expected to. More importantly our Mini-TES instrument, which we put in danger by the deep sleep operation, did survive the night and we hope it will survive more of these. But we're getting dangerously close to the cold temperatures that it isn't able to survive through."

But that doesn't mean the sensitive miniature thermal emission spectrometer -- Mini-TES -- won't suffer in the long run. After twice putting Opportunity into deep-sleep mode, NASA says it will start using that strategy on a regular basis, even though Mini-TES could be damaged if temperatures during the Martian winter nights drop low enough.

Still, both rovers, Opportunity and Spirit, have completed their missions. The extended lives of both machines is gravy for JPL, which used them to verify that ocean water once existed on Mars. Both rovers could continue to operate, gathering valuable data about the possibilities of life on Mars, for months to come.

FMI: www.jpl.nasa.gov