Managing Fleets of LEO Satellites: Nonlinear, Optimal, Efficient, Scalable, Usable, and Robust

Gregory Stock, Juan A. Fraire, Tobias Mömke, Holger Hermanns, Fakhri Babayev, Eduardo Cruz

Abstract

Size and weight limitations of Low-Earth Orbit (LEO) small satellites make their operation rest on a fine balance between solar power infeed and power demands of communication technologies on board, buffered by on-board battery storage. As a result, the problem of planning battery-powered payload utilization together with inter-satellite communication is extremely intricate. Nevertheless, there is a growing trend towards constellations and mega-constellations that are to be managed using sophisticated software support. Earlier work has leveraged cost-optimal reachability in priced timed automata for deriving near-optimal finite-horizon schedules to operate a single LEO satellite in orbit. This paper harvests that work and improves it in several dimensions, all needed for true in-orbit applicability. (1) The battery representation is no longer bound to be linear, but can be kinetic, which means that the optimization problem includes non-linearities. (2) The management is perpetuated by a receding horizon scheduling strategy. (3) The model is continuously improved with the latest telemetry received from orbit. (4) A tandem of satellites equipped with state-of-the-art inter-satellite link transponders is considered. (5) The core optimization problem is now solved using dynamic programming with antichain-based pruning, which is proven to be optimal and despite all the additional features outperforms the earlier approach by orders of magnitude. (6) The entire approach is grounded in the concrete requirements of the GomX-4 LEO mission. (7) Care is taken to make the approach usable by the space engineers, and robust against failures of parts of the tool chain. (8) An extensive test campaign validates accuracy, efficiency, scalability, and robustness with respect to the operational requirements and constraints of LEO constellations.

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