July 11, 2016 – NASA’s Curiosity Mars rover resumed full operations today, following work by engineers to investigate why the rover put itself into a safe standby mode on July 2. The rover team brought Curiosity out of safe mode on July 9.
The most likely cause of entry into safe mode has been determined to be a software mismatch in one mode of how image data are transferred on board. Science activity planning for the rover is avoiding use of that mode, which involves writing images from some cameras’ memories into files on the rover’s main computer. Alternate means are available for handling and transmitting all image data.
The rover put itself into safe mode on July 2, ceasing most activities other than keeping itself healthy and following a prescribed sequence for resuming communications.
Safe mode is an automated fault protection status that spacecraft are programmed to enter into when they sense conditions for which they do not have a specific response. While in this mode, a spacecraft suspends non-essential activities pending further instructions from ground controllers. Once a spacecraft enters safe mode, engineers on the ground work to quickly diagnose the problem and try to replicate the conditions that triggered the event. They can then use that information to take corrective actions, either by uplinking new commands or avoiding the action that caused the safe mode event.
Curiosity has entered safe mode three times previously, all during 2013.