NavIC and GAGAN: India's regional navigation constellation and its augmentation system for aviation

Background

Navigation with Indian Constellation (NavIC) is the regional navigation satellite system established by the Indian Space Research Organisation; it was earlier known as the Indian Regional Navigation Satellite System (IRNSS). NavIC is designed with a constellation of 7 satellites and a network of ground stations working round the clock. Three satellites are placed in geostationary orbit, at 32.5°E, 83°E and 129.5°E, and four in inclined geosynchronous orbit with equatorial crossings at 55°E and 111.75°E, at an inclination of 29°. It offers two services, the Standard Position Service (SPS) for civilian users and the Restricted Service (RS) for strategic users, in both the L5 (1176.45 MHz) and S band (2498.028 MHz); a new civilian signal is being introduced in the L1 band (1575.42 MHz). The coverage area includes India and a region up to 1500 km beyond Indian boundary, with user position accuracy better than 20m and timing accuracy better than 50ns. The International Maritime Organisation has recognised NavIC as a component of worldwide radio navigation system for maritime applications. GAGAN is a different thing: GPS Aided Geo Augmented Navigation, implemented by ISRO with the Airports Authority of India, is a satellite based augmentation system (SBAS) for Indian airspace that adds the accuracy, availability and integrity needed for phases of flight from en-route to approach. It is inter-operable with other such systems including the United States' WAAS, the European EGNOS and the Japanese MSAS, and has been certified by the Directorate General of Civil Aviation (DGCA) for RNP 0.1 and APV-1 services.