Experiences with Assurance Cases for Spacecraft Safing

Assurance cases are gaining momentum across several industries as a way to assure critical properties of engineered systems. In the space industry, they promise to help assure spacecraft safing, a fallback mode commonly included in spacecraft to respond to critical faults and keep the vehicle safe until ground operators can resolve the problem. We constructed an assurance case for one vehicle, generalized that case to create a domain-specific pattern, and then applied the pattern to a second vehicle. This paper describes these efforts and lessons learned.