Orbital Rendezvous: When is Autonomy Required?

The ability to control the relative motion of two orbiting spacecraft from the ground is approximately a function of four key parameters: relative state knowledge errors, maneuver execution errors, environment modeling errors, and the time delay between the execution of successive maneuvers. Based on these four parameters an assessment of the ground's capability to control relative position can be made and a minimum safe-approach distance can be determined. Approximate analytic expressions for minimum ground-controlled separations are presented and then validated with a detailed linear covariance analysis. The analytic expressions are shown to be accurate to within +/-25%.