An overview of the fault protection design for the attitude control subsystem of the Cassini spacecraft

This paper describes Cassini's fault tolerance objectives, and how those objectives have influenced the design of its attitude control subsystem (ACS). Particular emphasis is placed on the architecture of the software algorithms that are used to detect, locate, and recover from ACS faults, and the integration of these algorithms into the rest of the object-oriented ACS flight software. The interactions of these ACS "fault protection" algorithms with Cassini's system-level fault protection algorithms is also described. We believe that the architecture of the ACS fault protection algorithms provides significant performance and operability improvements over the fault protection algorithms that have flown on previous interplanetary spacecraft.