Guidance algorithm for the final translational phase of autonomous close range Rendezvous and Docking of spacecraft

An orbital maneuver during which two spacecraft starting from a remote distance arrive at the same orbit and approach to a closer distance is often termed a space rendezvous. Rendezvous requires a precise match of the orbital velocities of the two spacecraft which would allow them to remain at a constant distance throughout the mission. This paper proposes a novel guidance algorithm for the final translational phase of an autonomous close range Rendezvous and Docking mission, to guarantee trajectory safety. It ensures that the final translational maneuver is through a predetermined approach corridor. The proposed algorithm employs the linearized Clohessy Wiltshire equations to compute the reference positions and velocities. The multiple impulse firing strategy is utilized to effect the transfer, due to the significant reduction in the maximum trajectory deviation from the docking axis achievable. The trajectory safety is accounted for by the Line of Sight constraint and the Rendezvous and Docking durations satisfying the Line of Sight constraint are computed through the algorithm. An analytical method to determine the maximum trajectory deviation is also proposed and serves as a safety check. The proposed strategies provide a safe trajectory in the final phase of an autonomous Rendezvous and Docking mission where mission safety is critical.