Application of a Near-Optimal Feedback Guidance Algorithm to Spacecraft in Dynamically Complex Environments

A near-optimal feedback guidance algorithm is applied to several different applications in the Circular-Restricted Three Body Problem and in proximity operations in LEO modeled by Keplerian motion. In both scenarios gravitational perturbations are introduced in order to assess the algorithm's robustness. Two forms of the guidance algorithm are studied: a zero-effort miss/zero-effort velocity feedback control law and a zero-effort miss/zero-effort velocity feedback control law augmented with a sliding mode. Both guidance laws have previously been applied to the problems of planetary landing, asteroid intercept, and close-proximity maneuvers near an asteroid. This study is motivated by the growing interest in spacecraft autonomy for proximity operations and in cases where a high frequency of open-loop commanded maneuvers is not practical. Results demonstrate that nominal zero-effort miss/zero-effort velocity feedback guidance is suboptimal in all test cases, but performance can be improved through the addition of waypoints and tuning of guidance law parameters. Additionally, the application of a sliding-mode is shown to overcome limitations introduced by gravitational perturbations in some instances.