Flight Dynamics Modelling and Application to SatelliteDeorbitation Strategy

Sammanfattning: In this paper a study to determine the best strategic choice to deorbit satellites incase of system failures is conducted. An orbital mechanic analysis of the deorbitationis done and a matlab code based on Lagrange’s interplanetary equations is developed.The effects of the atmospheric drag and the solar activity are investigated and the fueland delta velocity consumptions are assessed for different deorbitation strategies. Thepaper also investigates the probability to hit or be hit by a piece of debris. A briefoverview of the acquisition and safe hold modes Bdot and Bspin is given. Then thepossibility to deorbit a satellite working in these attitude and orbit control modes fromlow Earth’s orbits is studied. An attitude and orbit simulator is used to analyze theevolution of the attitude during a manoeuvre, in particular the effect of the thrusters’misalignment is investigated. A strategy which combines manoeuvres and aerobrakingis chosen and its implementation on different types of orbits is studied. The paperconcludes that the necessary manoeuvres for a 25 years deorbiting time can be achieveif the spacecraft has a functional acquisition and safe hold mode and an operationalpropulsion system. In the end an alternate mode based on star trackers and reactionwheels is developed to avoid most of the activations of the acquisition and safe holdmode and to eventually perform the end of life disposal of a spacecraft.