Autonomous navigation of small co-orbiting satellites using C/A GPS code

摘要

Abstract: With the advent of the space station era, a large increase in the volume of the traffic in low earth orbit is anticipated; current methods of monitoring and controlling orbital operation from the ground will not always be feasible. Therefore, the emphasis in spacecraft design and mission planning must be directed toward decreased dependence upon ground support. The first step toward increased autonomy for space activities is the development of reliable on- board navigation and rendezvous techniques. The NAVSTAR Global Positioning System provides the nearest and primary tool for most on-board navigation applications. A combined absolute/relative navigation experiment, presently under analysis in Italy, is described: two space vehicles are constrained to take measurements from the same GPS satellites. The determination of the absolute and relative state vectors is carried out by a Kalman filter that processes the difference between the two vehicle measurements relevant to the same GPS satellites and the absolute measurements of each vehicle. The experiment is implemented with two small co-orbiting satellites, Pegasus/Scout II compatibles, flying in circular orbit at 400 km altitude and maneuvering to vary the distance between the two satellites. Absolute and relative position and velocity are autonomously computed on board the vehicles with accurate so good as to allow GPS-based rendezvous operations and autonomous navigation.!