A framework for the casualty risk assessment and lifetime determination of small satellites

On 16 December 2015, the National University of Singapore (NUS) launched two of its first small satellites - the 80kg class micro-satellite Kent Ridge-1, and the 2U CubeSat Galassia, into space. The event marked a milestone in the history of Singapores nascent space industry. Regulatory requirements of the country mandate that pre-launch and post-launch casualty risk assessments be performed in the aspects of collision and re-entry of spacecraft, specifically on 1) determining orbit lifetime of the satellites; 2) calculating the re-entry casuality risk probability of the spacecrafts, and 3) estimating the in-orbit collision risk probability. We present a systematic framework for the casualty risk assessment of small satellites, developed based on field experience with the Kent Ridge-1 and Galassia. Based on this framework, we evaluate both Kent Ridge-1 and Galassia to have been launched safely without collision into orbit, and after their approximate kinematic lives of 21.2 and 7.3 years respectively, will be burnt off completely. Even in the statistically possible event that any residue should persist upon re-entry, the probability of this residue resulting in casualty is less than 10 −4 .