A step towards initial Satellite based Navigation Services in India: GAGAN & IRNSS

The Indian Space Research Organization (ISRO) and Airports Authority of India (AAI) have implemented the GPS Aided Geo Augmented Navigation-GAGAN project as a Satellite Based Augmentation System (SBAS) for the Indian Airspace. The objective of GAGAN to establish, deploy and certify satellite based augmentation system for safety-of-life civil aviation applications in India has been successfully completed. The system is inter-operable with other international SBAS systems like US-WAAS, European EGNOS, and Japanese MSAS etc. GAGAN GEO footprint extends from Africa to Australia and has expansion capability for seamless navigation services across the region. GAGAN provides the additional accuracy, availability, and integrity necessary for all phases of flight, from enroute through approach for all qualified airports within the GAGAN service volume. GAGAN Payload is already operational through GSAT-8 and GSAT-10 satellites. The third GAGAN payload will be carried onboard GSAT-15 satellite which is scheduled for launch this year.

Initially, Director General of Civil Aviation (DGCA) certified GAGAN for enroute operations (RNP 0.1) on December 30, 2013 and subsequently on April 21, 2015 for precision approach services (APV 1). APV1 Certified GAGAN signals are being broadcast with effect from May 19, 2015. GAGAN is the first SBAS system in the world to serve the equatorial region. GAGAN ionospheric algorithm known as ISRO GIVE Model-Multi-Layer Data Fusion (IGM-MLDF) was developed by ISRO and is operational in the implemented GAGAN System. India has become the third country in the world to have such precision approach capabilities.

GAGAN though primarily meant for aviation, will provide benefits beyond aviation to many other user segments such as intelligent transportation, maritime, highways, railways, surveying, geodesy, security agencies, telecom industry, personal users of position location applications etc.

IRNSS, the Indian Regional Navigation Satellite System, is an ISRO initiative to design and develop an independent satellite-based navigation system to provide positioning, navigation and timing services for users over Indian region. The system is designed with a constellation of 7 spacecraft and a vast network of ground systems operating. The first three satellites (IRNSS-1A, 1B &1C) were launched in 2013-14.

IRNSS-1D, the fourth satellite of IRNSS constellation was successfully launched on March 28, 2015 on board PSLV-C27. The initial tests of the spacecraft have been successfully completed and it has joined the family of IRNSS space segment. With the addition of fourth spacecraft the minimum satellite requirement is met and independent position solution is demonstrated for the first time using an Indian satellite-based navigation system. The unique Geostationary Earth Orbit (GEO) /Geo Synchronous Orbit (GSO) constellation design provides a position accuracy of better than 15 metre for longer duration of 20 hours in a day even with 4 satellites.

ISRO has released the ‘IRNSS Signal-in-Space interface control document for Standard Positioning Service ver 1.0’, the document that comprehensively provides all the information required by user receiver manufacturers. The document is available for download at http://irnss.isro.gov.in.

While GAGAN will redefine navigation over Indian Airspace, IRNSS will provide independent and self reliant satellite based navigation services over Indian region.