Geostationary repeaters: a low cost way to enhance civil user performance of GPS and GLONASS

Inmarsat proposes to implement a set of geostationary repeaters operating in the navigation L-band (approximately 1575 MHz) to serve as an overlay to the GPS (Global Positioning System) and GLONASS (the Soviet global navigation satellite system). One major motivation for the overlay is the need expressed by the aeronautical community for an independent, quick response (10 s) external integrity channel. An additional advantage of a navigation band solution is that it would be received by (virtually) unmodified GPS and/or (slightly) modified GLONASS receivers. The integrity, coverage, availability, and timing enhancements that are possible from geostationary augmentation to GPS are discussed. A description of the Inmarsat pseudonoise (PN) test program where GPS-compatible PN-signal formats are transmitted through current Inmarsat satellites is presented to demonstrate the simplicity and practicality of the geostationary repeater augmentation technique.<>