Cassini Attitude and Articulation Control Subsystem Fault Protection Challenges During Saturn Proximal Orbits

Abstract

is the largest and most ambitious interplanetary spacecraft in history. As the first spacecraft to achieve orbit at Saturn, Cassini has collected science data throughout its fouryear prime mission (2004-08), and has since been approved for a first and second extended mission through 2017. As part of the final extended mission, Cassini will begin an aggressive and exciting campaign of high inclination low altitude flybys within the inner most rings of Saturn, skimming Saturn's outer atmosphere, until the spacecraft is finally disposed of via planned impact with the planet. This final campaign, known as the proximal orbits, presents unique fault protection related challenges, the details of which are discussed in this paper. NomenclatureAACS = Attitude and Articulation Control Subsystem CBH = Catbed Heater FP = Fault Protection FSDS = Flight Software Development Suite FSW = Flight Software ITL = Integrated Test Laboratory ME = Main Engine MPD