Configuration Study of the Navsat System Satellites

摘要

NAVSAT configurations using circular, geosynchronous, and highly eccentric orbits were studied. A civil navigation system based on a combination of satellites placed in geosynchronous and Molniya type orbits seems feasible. The proposed TDMA approach consists of a frame with nine bursts separated by a guard time of 105 msec to avoid overlap between bursts. Antipodal satellites share the same time slot. The down link frequency is 1.956 GHz. The satellite constellation consists of six navigation packages in geosynchronous orbit and 12 satellites in highly eccentric orbits. Each elliptic orbit inclined 63.4 deg with respect to the equatorial plane, carries two spacecraft. Three elliptic orbits present the apogee over the north pole and the other three over the south pole. The apogee and perigee altitude are 39,114 Km and 1250 Km respectively. The constellation guarantees a minimum of four visible satellites.