Critical Sizes of Satellite Constellations

The precipitous growth of commercial space activity, largely from the development of satellite constellations, threatens to produce a runaway orbital debris population. National regulators are attempting to limit these risks through orbital debris mitigation requirements, but these fail to address the large scale and long lifetimes of satellite constellations. Instead, evaluations are based on the risks from single satellites, and the aggregate risks across constellations are neglected. This situation arises in part because of a lack of suitable approaches to evaluate constellation plans. Here a simple analytical approach reveals that several planned, partially deployed, or fully deployed constellations exceed their critical size producing an unstable or a runaway orbital debris population. Worryingly, this occurs both for small and large constellations, despite debris mitigation measures that go beyond internationally recognised good practices, and even when the constellations are deployed into a pristine, debris-free orbital environment. The results demonstrate the need for more stringent approaches to regulation and suggest careful consideration of some recent constellation plans.