Low-thrust guidance scheme for Earth-capture trajectories

A new guidance scheme for the Earth-capture phase of a low-thrust spacecraft is developed. The objective of the guidance scheme is to provide the appropriate thrust steering program that will transfer the vehicle from hyperbolic conditions near the Earth's sphere of influence to a circular low-Earth orbit. Blending two control laws that reduce energy and eccentricity, respectively, generates the steering angle commands. The presented guidance design is predictive in nature and does not rely on a stored reference trajectory or reference controls. The guidance algorithm iterates on a single guidance parameter (a blending coefficient) such that a desired performance measure is minimized and boundary conditions are satisfied. Numerical simulations of three-dimensional guided capture trajectories are presented, and results show that the guidance successfully performs the high-energy Earth-capture maneuver. The simplicity of the guidance design makes it a viable candidate for onboard implementation.