Nonlinear tracking control for satellite formations

A tracking control law using a sliding mode framework is derived to control a satellite formation. Hill's relative motion equations are used to model the follower satellite's motion relative to the leader. To minimize fuel required to maintain the formation, each satellite is constrained to reside near a natural orbit. Control forces axe applied only to maintain the desired relative motion by correcting for initial offsets and perturbation effects that tend to disperse the formation. The control law is modified to account for the discontinuous nature of the control forces available with the satellite propulsive thrusters. Numerical simulations using a high-fidelity, nonlinear model demonstrate the control law performance for the full nonlinear dynamics with high order perturbations.