Battery-Aware Scheduling in Low Orbit: The GomX–3 Case
When working with space systems the keyword is resources. For a satellite in orbit all resources are sparse and the most critical resource of all is power. It is therefore crucial to have detailed knowledge on how much power is available for an energy harvesting satellite in orbit at every time – especially when in eclipse, where it draws its power from onboard batteries. This paper addresses this problem by a two-step procedure to perform task scheduling for low-earth-orbit (LEO) satellites exploiting formal methods. It combines cost-optimal reachability analyses of priced timed automata networks with a realistic kinetic battery model capable of capturing capacity limits as well as stochastic fluctuations. The procedure is in use for the automatic and resource-optimal day-ahead scheduling of GomX–3, a power-hungry nanosatellite currently orbiting the earth. We explain how this approach has overcome existing problems, has led to improved designs, and has provided new insights.
KeywordsBattery State Battery Model Time Automaton Battery Depletion Compute Schedule
This work has received support from the EU 7th Framework Programme project 318490 (SENSATION), by the European Space Agency under contract number RFP/NC/IPL-PTE/GLC/as/881.2014, by the ERC Advanced Investigators Grant 695614 (POWVER), and by the CDZ project 1023 (CAP). We are grateful to Boudewijn Haverkort and Marijn Jongerden (both from Universiteit Twente), Kim Larsen, Marius Mikučonis, Erik Ramsgaard Wognsen (all from Aalborg University), and all further participants of SENSATION as well as experts at GomSpace for very fruitful discussion and support.
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