  The paper considers the application of feedback control to orbital transfer
maneuvers subject to constraints on the spacecraft thrust and on avoiding the
collision with the primary body. Incremental reference governor (IRG)
strategies are developed to complement the nominal Lyapunov controller, derived
based on Gauss Variational Equations, and enforce the constraints. Simulation
results are reported that demonstrate the successful constrained orbital
transfer maneuvers with the proposed approach. A Lyapunov function based IRG
and a prediction-based IRG are compared. While both implementations
successfully enforce the constraints, a prediction-based IRG is shown to result
in faster maneuvers.
