Sensing Technologies for Formation-Flying Spacecraft in LEO using CDGPS and an Interspacecraft Communications System

摘要

This paper describes research on sensing technologies for formation-flying spacecraft in low earth orbit. The approach is based on a combination of carrier-phase differential GPS (CDGPS) sensors and GPS-like transceivers that are combined with the interspacecraft communications system. By providing additional inter-spacecraft range and Doppler measurements to the navigation solution, these on-board transmitters could facilitate the use of CDGPS for orbits in which adequate visibility /geometry to the NAVSTAR constellation is not available. In addition, the carrier-phase cycle ambiguity can be rapidly initialized using relative vehicle motions. The paper discusses this augmentation concept in detail and presents a new algorithm that significantly improves the bias initialization process. The paper also addresses some key measurement errors associated with formation-flying spacecraft separated by long baselines (10-100 km). Experimental results on a new terrestrial testbed are presented to show the vehicle formation undergoing short path initialization and formation maneuvers.