Assessing and Minimizing Collisions in Satellite Mega-Constellations

Abstract

The aim of this thesis is to provide satellite operators and researchers with an efficient means for evaluating and mitigating collision risk during the design process of mega-constellations. Current algorithms and software tools for assessing collision probabilities of satellites are not sufficiently robust for the forthcoming orbital environment with the deployment of many thousands of telecommunications satellites in low-Earth orbit (LEO). First, a baseline for evaluating various techniques for close-encounter prediction and collision-probability calculation (Hoots et al. 1984, Gronchi 2005, JeongAhn and Malhotra 2015) is established by carrying out brute-force numerical simulations and using a sequence of filters to greatly reduce the computational expense of the algorithm. Next, conjunction events in the orbital environment following the anticipated deployments of the OneWeb LEO and SpaceX Starlink mega-constellations are estimated. As a final step, Minimum Space Occupancy (MiSO) orbits (Bombardelli et al. 2020), a generalization of the well-known frozen orbits that account for the perturbed-Keplerian dynamics of the Earth-Moon-Sun-satellite system is investigated. The ability of MiSO configurations of the proposed mega-constellations, as suggested by Bombardelli et al. 2018, to reduce the risk of endogenous (intra-constellation) collisions is evaluated. The results indicate that the adoption of the MiSO orbital configuration can significantly reduce risk with nearly indistinguishable adjustments to the nominal orbital elements of the constellation satellites.