The Cassini mission risk assessment framework and application techniques

The Cassini space mission is intended to investigate the planet Saturn and its ring system. Due to the low intensity of solar radiation, solar batteries are not adequate for this mission and radioisotope thermoelectric generators (RTGs) are utilized to supply the electric power to the spacecraft systems. The presence of a radioactive material on board and the consequences of a potential accident during the launch and near-earth phases of the mission require a scrupulous process of risk assessment to be executed before launch approval is granted at the highest level. For this purpose, the probabilistic risk assessment (PRA) approach has been chosen and applied throughout the analysis process. This paper describes the Cassini PRA methodology and presents the steps which have been accordingly executed to develop potential launch accident scenarios and their quantification.