A Radiation-Reliability Assurance Case using Goal Structuring Notation for a CubeSat Experiment

Abstract

CubeSats have become an attractive platform for university-based spacecraft designs because they are cheaper and quicker to launch than full-scale satellites. One way of keeping costs for CubeSats low is using commercial off-the-shelf parts (COTS) instead of using space-qualified parts. Space-qualified parts are often costly, larger, and consume more power than their commercial counterparts prohibiting their use within a CubeSat. Given typical power budgets, monetary budgets, and timelines for CubeSat missions, conventional radiation hardness assurance, like the use of hardened parts and radiation testing campaigns of COTS parts, is not possible, requiring a system-level approach to radiation effects mitigation. In this thesis an assurance case for the radiation reliability of a CubeSat experiment is expressed using Goal Structuring Notation (GSN), a graphical argument standard. The case specifically looks at three main mitigation strategies for the radiation environment: total ionizing dose (TID) screening of parts, detection and recovery from single-event latch-ups (SEL) and single-event functional interrupts (SEFI). The graphical assurance case presented makes a qualitative argument for the radiation reliability of the CubeSat experiment using part and system-level mitigation strategies and is supported by functional and system models of the system.