Constant-magnitude low-thrust orbital transfer with final-approach targeting

Satellite orbit control is essential for numerous space missions, requiring both fuel efficiency and accuracy in the presence of orbital perturbations. Thus far, however, little attention has been given to developing low-thrust closed-loop orbit control with guaranteed stability, accuracy, and performance, while accounting for the constant-magnitude thrust constraint typical to electric propulsion (EP) systems. This research develops a new closed-loop Lyapunov-based control law for low-thrust orbital transfers using the Milankovitch vectorial elements, with a particular emphasis on constant-magnitude thrust systems. Although EP systems are highly fuel-efficient, their constant-magnitude thrust attribute introduces challenges that have been scarcely addressed in previous works. This work suggests a new method to solve these challenges by adopting an integrative approach, wherein the closed-loop orbital transfer algorithms combine a Lyapunov-based controller with linear quadratic regulation and sliding-mode control. Simulations indicate that, compared to existing methods, the newly-proposed integrative approach improves transfer accuracy while guaranteeing stability, eliminating chattering and reducing propellant consumption for transfers to near-circular target orbits.