GPS Aided Geo Augmented Navigation

The GPS Aided Geo Augmented Navigation or GPS and Geo Augmented Navigation system (GAGAN) is a planned implementation of a regional Satellite Based Augmentation System (SBAS) by the Indian government, which is a system to improve the accuracy of a GNSS receiver by providing reference signals. The Rs. 7,740,000,000 (774 crore) project is being implemented in three phases through 2008 by the Airport Authority of India with the help of the Indian Space Research Organization's (ISRO) technology and space support. The goal is to provide navigation system for all phases of flight over the Indian airspace and in the adjoining area. It is applicable to safety-to-life operations, and meets the performance requirements of international civil aviation regulatory bodies. The final, operational phase of GAGAN is likely to be completed by May 2011. "Gagan" is the transliteration of a Hindi word that means sky.

Technology

The project is being integrated with the geostationary satellite GSAT-4 and has a goal of being operational in 2008. [ [http://www.india-defence.com/reports/2239 ISRO, Raytheon complete tests for GAGAN Satellite Navigational System.] India Defense Website. 20 June 2006.] [K.N. Suryanarayana Rao and S. Pal. [http://www.aiaa.org/indiaus2004/Sat-navigation.pdf The Indian SBAS System – GAGAN] . Abstract from the India-United States Conference on Space Science, Applications, and Commerce. June 2004.] U.S. defense contractor Raytheon has stated they will bid to build the system. [ [http://www.india-defence.com/reports-3966 Raytheon to bid for Geosynchronous Augmented Navigation System (GAGAN) Project] ]

To begin implementing an SBAS over the Indian airspace, Wide Area Augmentation System (WAAS) codes for L1 frequency and L5 frequency were obtained from the United States Air Force and U.S Department of Defense on November 2001 and March 2005. [ [http://www.mycoordinates.org/gagan-update-arjunsingh-mar-06.php GAGAN Update Dr. Arjin Singh, Additional GM, Directorate of Global Navigation System, Airport Authority of India] ] . The system will use eight reference stations located in Delhi, Guwahati, Kolkata, Ahmedabad, Thiruvananthapuram, Bangalore, Jammu and Port Blair, and a master control center at Bangalore.

Technology Demonstration

As a part of the programme, a network of 18 total electron content (TEC) monitoring stations were installed at various locations in India to study and analyse the behaviour of the ionosphere over the Indian region. GAGAN's Technology Demonstration System (TDS) signal in space provides a three-metre accuracy as against the requirement of 7.6 metres. Flight inspection of GAGAN signal is being carried out at Kozhikode, Hyderabad and Bangalore airports and the results have been satisfactory so far. To study the ionospheric behavior more effectively over entire Indian Airspace, Indian universities and R&D labs, which are involved in the development of regional based IONO-TROP model for GAGAN, have suggested nine more TEC stations. [ [http://www.mycoordinates.org/gagan-update-arjunsingh-mar-06.php GAGAN Update Dr. Arjin Singh, Additional GM, Directorate of Global Navigation System, Airport Authority of India] ] The AAI’s efforts towards implementation of operational SBAS can be viewed as the first step towards introduction of modern CNS/ATM system over Indian airspace [ [http://www.mycoordinates.org/gagan-update-arjunsingh-mar-06.php GAGAN Update Dr. Arjin Singh, Additional GM, Directorate of Global Navigation System, Airport Authority of India] ] .

Technology Integration

GAGAN, after its final operational phase completion, will be compatible with other SBAS systems such as the Wide Area Augmentation System (WAAS), the European Geostationary Navigation Overlay Service (EGNOS) and the Multi-Functional Satellite Augmentation System (MSAS) and will provide seamless air navigation service across regional boundaries. While the ground segment consists of eight reference stations and a master control centre, which will have sub systems such as data communication network, SBAS correction and verification system, operations and maintenance system, performance monitoring display and payload simulator, Indian land uplinking stations will have dish antenna assembly. The space segment will consist of one geo-navigation transponder.

Indian Regional Navigational Satellite System

The Indian government has stated that it intends to use the experience of creating the GAGAN system to enable the creation of an autonomous regional navigation system called the Indian Regional Navigational Satellite System (IRNSS) and that it might use the GSAT-4 satellite as a technology demonstration system phase of the proposed navigational system. [ [http://www.isro.org/newsletters/spaceindia/aprsep2006/Satnavindustry.htm SATNAV Industry Meet 2006] . ISRO Space India Newsletter. April - September 2006 Issue.]

Effective Flight Management System

Flight Management System based on GAGAN will then be poised to save operators time and money by managing climb, descent and engine performance profiles. The FMS will improve the efficiency and flexibility by increasing the use of operator-preferred trajectories.It will improve airport and airspace access in all weather conditions, and the ability to meet the environmental and obstacle clearance constraints. It will also enhance reliability and reduce delays by defining more precise terminal area procedures that feature parallel routes and environmentally optimised airspace corridors.

* GAGAN will increase safety by using a three-diemensional approach operation with course guidance to the runway, which will reduce the risk of controlled flight into terrain i.e, an accident whereby an airworthy aircraft, under pilot control, inadvertently flies into terrain, an obstacle, or water.
* GAGAN will also offer high position accuracies over a wide geographical area like the Indian airspace. These positions accuracies will be simultaneously available to 80 civilian and more than 200 non-civilian airports and airfields and will facilitate an increase in the number of airports to 500 as planned. These position accuracies can be further enhanced with ground based augmentation system.

See also

* Global Positioning System
* GNSS Augmentation
* Wide Area Augmentation System
* MSAS

References