Quantitative Performance for Spacecraft Rendezvous Trajectory Safety

Safety requirement represents one of the most critical aspects when defining the operational profile for a rendezvous mission, especially with the development of autonomous spacecraft rendezvous. A quantitative safety performance index of spacecraft rendezvous trajectory with considering navigation errors and control errors is proposed, which involves the minimum distance between the 3σ ellipsoid of the chaser vehicle and the control zone of the target vehicle and the maximum instantaneous collision probability of these two vehicles. The former is to quantity degree of safety under the condition of no intersection between the 3σ ellipsoid and the control zone, while the latter is to quantity the collision probability when they intersect. The detailed definition of the safety performance index and the simplified calculation methods are provided. The efficiency and effectiveness of this safety index are testified by an example. The different influences of the transfer time, the number of impulses, and the intervals of impulses on the trajectory safety characteristic are analyzed. Several conclusions that would be useful for further safe rendezvous trajectory design are obtained.