A GPS Receiver for High-Altitude Satellite Navigation

Although GPS has found wide application for precision spacecraft navigation and formation flying applications in low Earth orbit (LEO), its application to geosynchronous (GEO) and other high-altitude missions has been limited to an experimental role because of the sparsity and weakness of the GPS signals present there. To fill this gap, NASA Goddard Space Flight Center (GSFC) has developed a new space-borne GPS receiver called Navigator that can operate effectively in the full range of Earth orbiting missions from LEO to GEO and beyond. Navigator employs special signal processing algorithms in radiation-hardened hardware that enable very fast signal acquisition capabilities and, more importantly, greatly improved sensitivity (a 10-dB improvement over previous space-based GPS receivers). Because of these unique capabilities, Navigator has generated a large amount of interest in the spacecraft navigation community. The first flight version of the receiver has been integrated into a relative-navigation experiment on the Shuttle-based Hubble Space Telescope Servicing Mission 4, due to launch in 2009. Navigator will be also serving as a critical navigation sensor on NASA´s Magnetospheric Multiscale mission, which is one of NASA´s first high-altitude formation-flying missions, NASA´s Global Precipitation Measurement mission, and the Air Force Research Lab´s Plug-and-Play spacecraft. Finally, key aspects of the Navigator design are being integrated into a GPS receiver being developed for NASA´s Orion Crew Exploration Vehicle.