The Mars Exploration Rover Project received confirmation from Mars Wednesday that the rover was back under ground control, executing a sequence of commands sent by the rover team, the space agency announced.
Communication with the rover had been minimal as Mars passed behind the sun as seen from Earth, a phase called solar conjunction that lasted about 3 weeks, and NASA said the rover automatically put itself into a standby state during that period.
Opportunity apparently put itself into that state on April 22 after sensing a problem during a routine camera check, mission officials said.
"We found the rover in a standby state called automode, in which it maintains power balance and communication schedules but waits for instructions from the ground," John Callas of NASA's Jet Propulsion Laboratory in Pasadena, Calif., said. "We crafted our solar conjunction plan to be resilient to this kind of rover reset, if it were to occur."
Opportunity has been working on Mars for more than nine years, while NASA's other Mars rover, Curiosity -- which landed last year -- is also nearing the end of its solar conjunction moratorium on commands.