Model-Based Assurance for Satellites with Commercial Parts in Radiation Environments

Small satellite projects often do not have the budget or schedule to incorporate radiation-hardened parts or extensive radiation test campaigns into their schedule. Yet a case must be made that the spacecraft will function as intended in orbit, with radiation, temperature and vacuum affecting part performance. The Vanderbilt Institute for Space and Defense Electronics, with support from NASA HQ, NASA NEPP, and NASA JPL, has developed a platform for making a safety case for systems with commercial (non-hardened) parts, called the Systems Engineering Assurance and Modeling (SEAM) platform. The platform has three elements: goal structuring notation (GSN), systems engineering models (SysML and our extensions), and Bayesian networks (BN). The GSN is a visual argument structure that presents an argument that the system meets specifications based on goals, strategies, and evidence. The systems engineering model is a high-level descriptive language that captures the spacecraft design and system architecture through various diagrams. We extend the SysML diagram set to include fault propagation diagrams, which map the environment, failure manifestations, anomalies, failure effects and responses (mitigation measures) of components and systems. The SEAM platform provides a low-cost alternative to conventional radiation hardening assurance paradigms.