Optimization techniques for satellites proximity maneuvers

The main topic of this dissertation is the control optimization problem for satellites Rendezvous and Docking. Saving resources is almost as important as the mission safeness and effectiveness. Three different numerical approaches are developed. The first two techniques deal with realtime and sub-optimal control, generating a reliable control sequence for a chaser spacecraft which eventually docks to a target. The first approach uses dynamic programming to quickly generate a sub-optimal control sequence on a predetermined path to be followed by one of the two vehicles involved into the docking operations. The second method presents a fast direct optimization technique, which was previously validated on real aircraft for trajectory optimization. The third approach aims to take into account the limitations of space qualified hardware, in particular thrusters. The new technique fuses the use of a set of low thrust on-off engines with impulsive-high-thrust engines. The hybrid method here developed combines and customizes different techniques. The relative motion in the above mentioned control strategies is represented by a linear dynamic model. As secondary topic of this dissertation, the use of a genetic algorithm optimizer to find possible conditions under which spacecraft relative motion can be periodic, or at least bounded, is presented. This analysis takes into account the J2 gravity perturbation and some drag effects. The importance of the obtained results directly apply to the problem of formation keeping, as natural dynamics can be exploited to reduce the amount of active control preventing the spacecrafts to drift apart along time