Perspectives on Dependable Computing for Solar System Exploration

25 years of continuous operation-now renamed Voyager Interstellar Mission Can operate until 2020 based on available power and attitude control propulsion With some loss of subsystem redundancy, operates with full science payload Spacecraft has extensive autonomous fault-detection and protection capabilities covering multitude of possible failures. Designed using radiation hard parts and extensive shielding. Galileo *The spacecraft is now fully recovered from yesterday's anomaly in which the onboard fault protection routines detected a despun bus reset about 28 minutes before the closest approach to Io. Because this could be a potentially harmful event, the spacecraft put itself into a safe mode and canceled the science sequence. The flight team worked throughout the day and evening to re-establish nominal spacecraft operations and to acquire the final track of recorded data. Unfortunately, three tracks of data all planned for recording within hours of closest approach to Io were lost because of the spacecraft problem. At this time we think the problem resulted from the radiation environment near Jupiter. NASA's Galileo spacecraft is out of safing mode and has resumed normal flight operations, including playback of pictures and other science data gathered during the January 3 1 Europa flyby. Four hours after that flyby, Galileo entered safing mode-a built-in protection mode designed to turn off all non-essential spacecraft activities-while the spacecraft was performing a sun acquisition turn. The turn was halted when onboard fault protection software determined that the turn was lasting longer than it should have. Normal operations of the spacecraft were restored Wednesday, February 10, and the playback of science data resumed Thursday morning, February I I. All observations made by Galileo's instruments during the close approach to Europa on January 3 1 were successfully stored and are being transmitted to Earth. After Galileo entered safing mode, scientists were unable to make planned distant observations of Europa, Io and Jupiter. Only four hours before the flyby, while Galileo was being bombarded by strong radiation near Io, its onboard computers reset and placed the spacecraft into standby mode. Onboard fault protection software told the spacecraft cameras and science instruments to stop taking data and enter a safe state until further instructions were received from the ground.