Navigation and orbit computation aspects of the ESA NAVSAT system concept

The requirements of a civilian, low-cost NAVSAT version of the GPS system are discussed. Six regional ground control facilities would compensate for the lack of autonomous navigation capabilities on the 24 NAVSAT spacecraft, a cost-saving measure. A 12 hr orbit for each satellite would yield two passes per day. The stations would maintain continuous uplinks to provide the satellites with navigational guidance for maintaining precision orbits. Continuous links would mandate data compression techniques to increase the data density by a factor of 600 to enable handling the spacecraft with six stations. It is concluded that the NAVSAT system could provide users with position accuracy better than 10 m and velocity data accurate to 10 cm/sec.