The Use of the Expanded FMEA in Spacecraft Fault Management

The NASA/APL Parker Solar Probe (PSP) mission will revolutionize our understanding of the Sun by swooping to within 4 million miles of the Sun's surface. This mission targets the fundamental processes and dynamics that characterize the Sun's corona and outwardly expanding solar wind and will be the first mission to fly into the low solar corona (i.e., the Sun's atmosphere) revealing both how the corona is heated and how the solar wind is accelerated. PSP has many engineering challenges presented by the intense environment in terms of heat, solar radiation, and reaction time to “safe” the spacecraft (displayed in Figures 1 and 2). The fault management system is highly autonomous and is designed to manage the complex system robustness as well as manage fault detection and response in a timely manner. The fault management design relies heavily on the Failure Modes and Effects Analysis (FMEA) which uses a systematic approach to determine the effects of each potential failure mode on that particular component/system, the spacecraft, and the mission. Once the potential effects are determined, then each failure mode is assigned a severity level, commensurate with the potential effects. For the PSP mission, the spacecraft functional FMEA was expanded to also include information about whether or not a failure mode was detectable by the spacecraft or by personnel on the ground, the timeframe for detection, and what mitigation was available to the mission team, if any. The Fault Management Team then used the FMEA to ensure that all faults had been captured, identify which faults could be detected by the spacecraft, and to build appropriate responses for the spacecraft to take during the mission.