Spacecraft relative motion planning is concerned with the design andexecution of maneuvers relative to a nominal target. These types of maneuversare frequently utilized in missions such as rendezvous and docking, satelliteinspection and formation flight where exclusion zones representing spacecraftor other obstacles must be avoided. The presence of these exclusion zones leadsto non-linear and non-convex constraints which must be satisfied. In thispaper, a novel approach to spacecraft relative motion planning with obstacleavoidance and thrust constraints is developed. This approach is based on agraph search applied to a virtual net of closed (periodic) natural motiontrajectories, where the natural motion trajectories represent virtual net nodes(vertices), and adjacency and connection information is determined byconditions defined in terms of safe, positively-invariant tubes built aroundeach trajectory. These conditions guarantee that transitions from one naturalmotion trajectory to another natural motion trajectory can be completed withoutconstraint violations. The proposed approach improves the flexibility of aprevious approach based on the use of forced equilibria, and has otheradvantages in terms of reduced fuel consumption and passive safety. Theresulting maneuvers, if planned on-board, can be executed directly or, ifplanned off board, can be used to warm start trajectory optimizers to generatefurther improvements.
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