Distributed orbit determination and observability analysis for satellite constellations with angles-only measurements

Autonomous absolute orbit determination (OD) for a satellite constellation using only inter-spacecraft measurements has considerable value in space systems engineering. This paper proposes a novel solution for cooperative autonomous OD for a system comprised of an arbitrary number of spacecraft, with inertial angles-only measurements. We establish a link between observability and a graph representation of measurements among spacecraft. For a system with a beacon or without beacons, it is shown that if a measurement graph topology has graph theoretic equivalence properties with a two-level tree form, the system is second-order and third-order locally weakly observable, respectively. To solve the distributed OD problem, the new interleaved distributed extended Kalman filter (IDEKF) is proposed. Several evaluation cases are designed to demonstrate the influence of measurement topology, number of spacecraft, and orbital configuration on the degree of system observability. Finally, the performance of the IDEKF estimation is illustrated for a ten-spacecraft constellation. (C) 2021 Elsevier Ltd. All rights reserved.