Space Debris Orbit and Attitude Prediction for Enhanced and Efficient Space Situational Awareness

Human space activity in the past 50 years has led to a plethora of man-made space debris which pose an imminent threat to global space operations. The current models of space debris orbits are not sufficient for detailed orbit prediction or for accurate tracking. This uncertainty manifests itself in Conjunction Analysis CA with active spacecraft, which leads to excessive orbital maneuvers which are both expensive and reduce the lifetime of satellites. Advances in orbit modelling will lead to better prediction of debris orbits and reduce the need for collision avoidance maneuvers, as well as minimizing the future pollution of the space environment through collisions. Most existing methods for analyzing the orbits of space debris do not take into account the effects of tumbling, and the attitude-dependent non-conservative forces are generally neglected. This study models the torques and attitude motion of uncontrolled man-made objects in orbit about the Earth, which tumble due to a combination of natural influences of the near-Earth space environment and initial angular momentum acquired during debris formation. The modelling of space debris is a relatively new field and represents a huge new area of research. The two main branches of this thesis are a modelling the torques that induce spin for objects in orbit, and b modelling the effect of certain attitude-dependent non-conservative forces on spinning objects in orbit. The main torque modelled in this study is solar radiation pressure SRP. Simulations of the radiation-induced torques are performed and the main mechanisms that lead to the tumbling of uncontrolled objects are analyzed. A novel method of presenting attitude-dependent forces and torques on space objects, dubbed Torque Maps, is presented. Radiation torques are caused by optical geometric asymmetry and can lead to oscillatory and secular changes in attitude.