NASA's Mars Reconnaissance Orbiter put itself into safe mode -- a precautionary status with minimized activities -- on March 14. It remained healthy and in communication with Earth, but with no science observations, while the flight team examined engineering data. On March 20, the team brought the spacecraft back out of safe mode.
Science instruments were powered up March 21 and are resuming normal science operations today, March 22.
When it went into safe mode, the spacecraft switched, for the first time in the mission, to a backup ("B") duplicate flight computer on board. Diagnosis of the "A" computer has not yet revealed what caused the switch to the B side.