Data-driven lifetime risk assessment and mitigation planning for large-scale satellite constellations

Abstract

We introduce a methodology for estimating the risk posed to the space environment by a spacecraft over an arbitrary period of time following a risk mitigation strategy, in terms of aggregate collision probability. Our methodology enables estimation of residual risk and maneuver frequency, where residual risk is defined conceptually as the risk to a spacecraft which remains even after adherence to a risk mitigation strategy. The key parameters considered which affect residual risk for a general risk mitigation strategy are the risk mitigation maneuver (RMM) threshold, the risk reduction factor, and the maneuver execution time. We present an analytic result regarding the necessary residual risk (per-satellite) to ensure the total aggregate collision probability of a satellite constellation of arbitrary size be below a target value. This approach offers a more complete model of spacecraft safety and potential risk to the space environment by studying more than just the RMM threshold, which has historically been used as a common benchmark in space situational awareness and regulatory compliance literature. Our analysis shows that the RMM threshold is but one of a few factors which have significant effects on residual risk. We provide evidence that the RMM threshold alone is an incomplete indicator of the actual risk posed to the space environment by an operational spacecraft. We demonstrate the effectiveness of this methodology by presenting numerical results which model realistic satellites and satellite constellations and draw key insights from this analysis which will aid in managing the safety and sustainability of the space environment and inform risk mitigation strategies for large satellite constellations.

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ORCID for Hugh G. Lewis: orcid.org/0000-0002-3946-8757

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