Autonomous Relative Navigation for Formation-Flying Satellites Using GPS

The Goddard Space Flight Center is currently developing advanced spacecraft systems to provide autonomous navigation and control of formation flyers. This paper discusses autonomous relative navigation performance for a formation of four eccentric, medium-altitude Earth-orbiting satellites using Global Positioning System (GPS) Standard Positioning Service (SPS) and "GPS-like" intersatellite measurements. The performance of several candidate relative navigation approaches is evaluated. These analyses indicate that an autonomous relative navigation position accuracy of 1 meter root-meansquare can be achieved by differencing high-accuracy filtered solutions if only measurements from common GPS space vehicles are used in the independentlyestimated solutions. 1 INTRODUCTION Formation-flying techniques and satellite autonomy will revolutionize space and Earth science missions and enable many small, inexpensive satellites to fly in formation and gather concurrent science data. The Guidance, Navigation, and Control Center (GNCC) at Goddard Space Flight Center (GSFC) has successfully developed high-accuracy autonomous satellite navigation systems using the National Aeronautics and Space Administration's space and ground communications systems and the Global Positioning System (GPS) [Gram 94, Hart 97]. Recently, the GNCC has leveraged this experience to develop advanced spacecraft systems that provide autonomous navigation and control of formation flyers. To support this effort, the GNCC is assessing the absolute and relative navigation accuracy achievable for proposed formations using GPS and "GPS-like" intersatellite measurements. Several universities and corporations are developing GPS transceivers that support this tracking concept for NASA and the Air Force Research Laboratory; these include Johns Hopkins Applied Physics Laboratory, International Telephone and Telegraph, Honeywell, Motorola, Jet Propulsion Laboratory, Cincinnati Electronics, and Stanford University [Baue 99]. Published flight data results ([Braz 96], [Schi 98], [More 98], [Kama 99]) have shown relative orbit determination performance at the meterto decameter-level using relative GPS pseudorange data for rendezvous and docking scenarios in low Earth orbits. This paper addresses the level of relative navigation performance achievable for a different class of missions, i.e. more than two vehicles maintaining a relatively tight formation, in a relatively ecentric orbit. This class of missions is represented by a tetrahedral formation designed to support a proposed mission to study the Earth's aurora. This formation consists of four satellites maintained in eccentric Earth orbits of approximately 500 by 7000 kilometer altitudes, with initial separations of 10 to 30 kilometers. Maneuvers would be performed monthly to maintain this configuration. To https://ntrs.nasa.gov/search.jsp?R=20000061967 2019-10-22T17:09:17+00:00Z