Guidance Algorithms for the Near-Distance Rendezvous of On-Orbit-Servicing Spacecraft

Abstract

This paper presents algorithms for the near-distance rendezvous of on-orbit-servicing spacecraft when approaching, departing and flying around a target vehicle in a circular orbit. These algorithms are based on the closed-form solution of linear Clohessy-Wiltshire equations and adapt the glideslope guidance used in the past for rendezvous and proximity operations of the space shuttle. By using the relationship of either power functions or piece linear functions between distance and speed, the multipulse glideslope approach and departure algorithms of the chaser can be applied at any time and in any direction in space for decelerating when approaching a target or a nearby location and accelerating when departing. The fly-around algorithm enables the chaser to circumnavigate a target in any plane and at any specified time. To save the pulse number for all algorithms, a way to solve the maximum allowable transfer interval between one pulse and the next one is presented, with consideration be given to the constraints about allowable safe velocity and allowable guidance error. Finally, several scenarios are simulated to illustrate these guidance algorithms.