Simulation of satellites and constellations for the assessment of collision avoidance operations

The recent rapid increase in the satellite population in low Earth orbit (LEO) causes the number of conjunctions between operational spacecraft to increase sharply as well. In order to be able to cope with the associated workload in the future, it is necessary to define precise and acceptable rules that determine which spacecraft has to evade and how the avoidance manoeuvres shall be performed. To enable the assessment of different conceivable rule sets, a holistic simulation framework has been developed within the “Rules4CREAM” (R4C) activity at the Technical University of Darmstadt. Based on current and expected trends in growth and distribution of satellites in LEO, long-term propagation in the order of years can be performed for arbitrary satellite populations with the R4C framework which enables the generation of realistic conjunction data. This paper presents the core modules of this simulation framework. The satellites are described by osculating Keplerian orbits and analytical models are implemented to represent the most dominant perturbations in LEO. Different modes of station keeping are depicted within the satellite operations module of the simulation. For constellations, a generic model has been developed that is able to model the simultaneous deployment of multiple constellation planes as well as other operational key aspects specific to constellations. The models are validated with other simulations and real-life data. Finally two methods for the all-on-all conjunction detection are examined and the number of detected conjunctions is compared.