An Availability Study for a Nav-Com Satellite System (NCSS) in Australia

To improve the reliability, accuracy and integrity of GPS SPS services for Civil Aviation and other precise navigation applications, Differential GPS and Ground Integrity Monitoring (GIC) techniques combined with a communication capability are required. In the United States, FAA is investigating the Wide Area Augmentation System (WAAS), which is GPS augmented by Geostationary satellites with GPS-like ranging capability. A satellite system with both communication and navigation functions, which includes either Geostationary satellites (GEO) or Low Earth Orbit (LEO) communication satellites is referred to as a Nav-Com Satellite System (NCSS). This paper examines the technical feasibilities for Australia of acquisition or deployment of a LEO based NCSS constellation, such as the IRIDIUM system, to provide an independent positioning service and/or a NCSS-based GPS-LEO augmentation system. After an overview of the IRIDIUM system and the introduction of NCSS positioning principal the navigation availability studies for IRIDIUM and the GPS-LEO augmentation system are presented. The result show that GPS augmented by the IRIDIUM system provides an efficient Wide Area Augmentation System and also that IRIDIUM in itself provides an independent regional navigation service for considerable large user groups.