Guidance and Control Strategies for the Collision-Avoidance Mode of a Satellite Pair Flying in Formation

Abstract. In this paper we present a study on the Collision-Avoidance mode of a formation flying satellite pair in which a free-flying chief spacecraft follows temporary off-nominal conditions and a controlled deputy spacecraft performs collision avoidance maneuvers. The Collision-Avoidance strategy consists in a Separation Guidance and a Nominal Guidance. The Separation Guidance is in charge of the avoidance of a predicted collision soon to occur, and it is based on a computationally simple, deterministic and closed-form algorithm, so that a valid solution is always available without delay. The Nominal Guidance uses Genetic Algorithms and it takes charge of placing the deputy spacecraft in a bounded safe or “parking” trajectory, while minimizing the propellant consumption and avoiding the evaporation of the formation. The performances of a Linear Quadratic Regulator and a Model Predictive Control are also compared in tracking the reference trajectories provided by the Collision- Avoidance strategy.