Single and Dual Burn Maneuvers for Low Earth Orbit Maintenance.

Optimal control theory suggests maintaining an orbital altitude band for Low-Earth-Orbiting (LEO) satellites using periodic thrusting than forced Keplerian motion, i.e. a trajectory obtained by thrust-drag cancellation. Designing guidance algorithm for orbit maintenance is complicated by the nonlinearities associated with orbital motion. An algorithm developed previously using thrusters firing significantly off the direction of motion successfully maintains an orbital band, but is very inefficient. This thesis develops two different control strategies based on the osculating orbital parameters. taking a conservative approach to keeping within altitude limitations. Thrust is in the local horizontal plane along the direction of flight. Single and dual burn maneuvers are considered for various bandwidths and thruster sizes. The dual burn strategy is somewhat close to a Hohmann transfer. The specified orbital band is generally maintained, with some cases slightly exceeding the upper limit. Propellant consumptions for both maneuvers is significantly better than previous methods. This thesis shows that forward firing thrusters can be used with osculating orbital parameters to obtain efficiencies within forced Keplerian motion values.