Safety Assessment And Mission Planning For GEO Rendezvous Under Spacecraft Colocation Constraints

On-orbit servicing in the geostationary orbit(GEO) which includes on-orbit maintenance, life extension and orbital debris removal is an important developing trend of astronautic technology in future. Rendezvous and docking is a premise of realizing on-orbit servicing. And trajectory safety is always an important requirement or judging index in rendezvous mission designing. Especially for GEO rendezvous, the colocation constraints and the non-cooperative targets bring new challenges to trajectory safety and mission proposal design. Around trajectory safe ty, this dissertation studies the safety assessment method of rendezvous trajectory, rendezvous mission planning method and relative navigation proposal design. The main results achieved in this dissertation are summarized as follows.A rendezvous trajectory safety quantitative pe rformance index eliminating probability dilution is developed.(1) Based on the physical meaning of the trajectory safety assessment elements containing ellipsoid distance, collision probability, warning threshold, a Monte Carlo simulation is proposed to demonstrate the correctness of the computation models.(2) The characteristics of the warning threshold varying with envelope radius, position error distribution, missing alarm probability and time are analyzed, and then a trajectory safety quantitative performance index eliminating probability dilution is defined by changing the mathematical relation between collision probability and warning threshold.The methods of safe mission arranging and trajectory optimization for GEO rendezvous under spacecraft colocation constraints are proposed.(1) Safety performance of the transition trajectories and the fly-around trajectory in GEO rendezvous under spacecraft colocation constraints is analyzed. A mission arranging method is proposed based on the results of safety performance analysis. Furthermore, a safety optimization model is built for mission arranging.(2) A fuel optimization model with safety constraints is built for multi- impulse closing trajectory, and the influences of maneuver proposal, impulse number, colocation constraint, and navigation precision on the optimization results are analyzed.The relative navigation proposal to a non-cooperative target which should satisfy the safety require ments is designed.(1) The measurement capability of general rendezvous sensors to a non-cooperative target is researched, then a relative navigation proposal which combines cameras and laser range finders is proposed.(2) The relative navigation models are respectively built based on different measurement information, and a simulation is performed to demonstrate whether the precision of the relative navigation proposal can satisfy the safety requirements of the rendezvous mission planning results.This dissertation develops the safety assessment method of rendezvous trajectory with uncertainty, and proposes the methods of safe mission arranging and trajectory optimization for GEO rendezvous under spacecraft colocation constraints, which have some theoretical significance. The arranged safe mission plan and optimized safe closing trajectory for GEO rendezvous, as well as the designed relative navigation proposal for a non-cooperative target, have high engineering reference value.