The Directorate General of Civil Aviation (DGCA) has successfully completed India’s first satellite-based landing system (SLS) approach on a commercial jet aircraft, using an IndiGo Airbus A320 at Maharana Pratap Airport in Udaipur, Rajasthan. The aircraft executed a Localiser Performance with Vertical Guidance (LPV) approach powered by GAGAN, India’s indigenous satellite-based augmentation system jointly developed by ISRO and the Airports Authority of India (AAI). This milestone extends satellite-guided precision landing capability from turboprop aircraft to mainline commercial jet operations for the first time in the country.
What Is GAGAN?
GAGAN stands for GPS Aided GEO Augmented Navigation. It is India’s Satellite-Based Augmentation System (SBAS), a navigation system that improves the accuracy, integrity, and reliability of standard GPS signals for aviation use. GAGAN does not replace GPS or function as an independent navigation system like India’s NavIC. Instead, it works as an overlay that corrects errors in GPS signals caused by atmospheric disturbances, satellite clock drift, and orbital inaccuracies, and then broadcasts the corrected data to aircraft.
The system was jointly developed by the Indian Space Research Organisation (ISRO) and the Airports Authority of India (AAI). An agreement between the two agencies was signed in August 2001, and GAGAN became fully operational in May 2015 after receiving certification from the DGCA. India is the fourth country in the world to have an indigenous SBAS, after the United States (WAAS), Europe (EGNOS), and Japan (MSAS). It is also the first SBAS to serve the equatorial anomaly region, where ionospheric disturbances are most severe and pose unique challenges for satellite navigation.
How GAGAN Works
GAGAN operates through three integrated segments that work together to deliver precision navigation data to aircraft cockpits.
The Ground Segment
A network of 15 Indian Reference Stations (INRES) is strategically placed across India at locations including Ahmedabad, Bengaluru, Delhi, Kolkata, Guwahati, Jammu, Nagpur, Porbandar, Port Blair, and Thiruvananthapuram. These stations continuously monitor raw GPS signals and detect errors caused by atmospheric conditions, satellite clock drift, and orbital deviations. The data is transmitted in real time to two Indian Master Control Centres (INMCC) located in Bengaluru and Delhi, which process the information, compute correction values, and generate integrity messages. The corrected data is then sent to three Indian Land Uplink Stations (INLUS) for broadcast to space.
The Space Segment
Three ISRO geostationary communication satellites carry the GAGAN navigation payload: GSAT-8 (launched 2011, positioned at 55 degrees East), GSAT-10 (launched 2012, 83 degrees East), and GSAT-15 (launched 2015, 93.5 degrees East). These satellites remain fixed over the Indian subcontinent at an altitude of approximately 35,786 kilometres and broadcast the correction signals on the L1 frequency (1575.42 MHz) , the same frequency used by GPS. This means aircraft with SBAS-capable GPS receivers can use GAGAN corrections without additional hardware.
The User Segment
Aircraft equipped with GAGAN-enabled GPS receivers receive both the raw GPS signals and the correction data from the geostationary satellites simultaneously. The onboard receiver applies the corrections to compute a highly accurate position, reducing errors from several metres to within 3 metres or better. This level of precision is essential for executing LPV approaches, especially during poor visibility or adverse weather conditions.
Analogy · How GAGAN Augments GPS Expand analogy
Think of GPS as a school clock that is sometimes a few minutes off. GAGAN is like a teacher who checks the clock against a precise wristwatch every second, notes the error, and announces the correct time over the school intercom so everyone in every classroom gets the accurate time instantly.
What Is a Satellite-Based Landing System?
A Satellite-Based Landing System (SLS) uses satellite navigation signals rather than ground-based radio transmitters to guide an aircraft during its final approach and landing. The conventional Instrument Landing System (ILS) relies on radio beams transmitted from equipment installed at the airport. While ILS is highly reliable, installing and maintaining it at every airport is expensive, costing several crores per runway end. This is why many smaller and regional airports in India operate without precision landing capability.
The LPV (Localiser Performance with Vertical Guidance) approach bridges this gap. It provides pilots with both lateral (left-right) and vertical (up-down) guidance that is functionally equivalent to an ILS approach, but without requiring any ground-based equipment at the airport. The guidance comes entirely from satellite signals augmented by GAGAN. An LPV approach can guide an aircraft down to 200 feet above the runway threshold, matching the performance of a Category I ILS.
During the Udaipur demonstration, the IndiGo Airbus A320 used an LPV approach to land at Maharana Pratap Airport. The aircraft’s onboard SBAS receiver processed GAGAN-corrected GPS signals to compute its precise position relative to the runway, enabling a safe and accurate landing. IndiGo had first introduced LPV operations on its ATR turboprop fleet in 2022 and has since expanded SBAS-enabled capability across its aircraft fleet.
Why This Milestone Matters for Indian Aviation
The successful SLS approach on a commercial jet has far-reaching implications for India’s aviation sector, which is one of the fastest growing in the world.
Safety at Smaller Airports
Nearly half of all Controlled Flight Into Terrain (CFIT) accidents worldwide occur during approach and landing phases that lack vertical guidance. LPV approaches address this vulnerability directly by providing precise vertical guidance down to 200 feet without requiring expensive ground installations. Airports that cannot justify the cost of an ILS can now offer precision approach capability using GAGAN, significantly improving safety margins.
AAI has already published 23 LPV approach procedures at airports across India, with plans to exceed 40 by the end of 2026. As more airports adopt these procedures, even remote airstrips in hilly or fog-prone regions can benefit from reliable satellite-guided approaches.
Reducing Weather-Related Disruptions
Flight delays, diversions, and cancellations due to poor visibility are a persistent challenge in Indian aviation, particularly during winter fog in northern India and monsoon conditions across the country. Satellite-based approaches are less susceptible to weather-related limitations compared to non-precision approaches that rely solely on pilot judgement. Wider deployment of GAGAN-enabled LPV procedures can reduce operational disruptions and improve on-time performance.
Lower Infrastructure Costs
Installing an ILS at a single runway end can cost ₹5 crore to ₹10 crore or more, with recurring maintenance expenses. SLS eliminates this need entirely by using space-based augmentation. For a country with more than 130 operational airports and plans to add many more under the UDAN regional connectivity scheme, the cost savings are substantial. The economic case for satellite-based landing is especially strong at smaller airports with lower traffic volumes.
A Boost for Regional Connectivity
The UDAN (Ude Desh ka Aam Nagrik) scheme, launched in 2016, aims to make air travel affordable and widespread by connecting underserved regional airports. Many of these airports lack ILS equipment. GAGAN-enabled LPV approaches can provide precision landing capability to these airports at minimal additional cost, directly supporting the government’s regional connectivity goals.
India’s Growing Satellite Navigation Ecosystem
The Udaipur demonstration is the latest milestone in India’s expanding satellite navigation capabilities. GAGAN’s journey began with a Technology Demonstration System (TDS) phase completed in 2007, followed by the Final Operational Phase (FOP) that led to full certification. The DGCA certified GAGAN for RNP 0.1 (Required Navigation Performance of 0.1 nautical miles) in December 2013 and for APV-1 (Approach with Vertical Guidance) in April 2015, making it the world’s first SBAS certified in the equatorial region.
Beyond aviation, GAGAN has applications in maritime navigation, railway operations, road transport, surveying, precision agriculture, and disaster management. The GAGAN Messaging Service (GMS) is already used by INCOIS (Indian National Centre for Ocean Information Services) to broadcast emergency alerts to fishermen at sea. More than 250 aircraft in India are currently equipped with GAGAN-enabled receivers, and this number is expected to grow rapidly as more airlines adopt the technology.
India also operates NavIC (Navigation with Indian Constellation) , an independent regional navigation satellite system comprising a constellation of satellites. Unlike GAGAN, which augments GPS signals, NavIC is a standalone system that provides positioning, navigation, and timing services over India and a region extending 1,500 kilometres beyond its borders. Together, GAGAN and NavIC give India a robust, dual-layered satellite navigation capability covering both augmentation and independent positioning needs.
| Feature | GAGAN | NavIC |
|---|---|---|
| Type | Satellite-Based Augmentation System (SBAS) | Independent Regional Navigation System |
| Function | Augments/corrects GPS signals | Provides independent position data |
| Coverage | Indian FIR and beyond (Africa to Australia) | India + 1,500 km beyond borders |
| Satellites | Payloads on 3 GSAT (GEO) satellites | 8 dedicated satellites (IRNSS series) |
| Primary Sector | Civil aviation | Strategic, civilian, and commercial |
| Year Operational | 2015 | 2018 (fully) |
Key Takeaways
- DGCA successfully conducted India’s first satellite-based landing system (SLS) approach on a commercial jet, an IndiGo Airbus A320, at Udaipur’s Maharana Pratap Airport using the GAGAN system.
- The aircraft executed a Localiser Performance with Vertical Guidance (LPV) approach, providing both horizontal and vertical guidance equivalent to a Category I ILS without ground-based equipment.
- GAGAN (GPS Aided GEO Augmented Navigation) is India’s Satellite-Based Augmentation System jointly developed by ISRO and AAI, using three geostationary satellites (GSAT-8, GSAT-10, GSAT-15) to broadcast GPS correction data.
- India is the fourth country in the world to have an indigenous SBAS, after the US (WAAS), Europe (EGNOS), and Japan (MSAS), and the first SBAS certified for the equatorial anomaly region.
- The GAGAN ground segment consists of 15 Indian Reference Stations (INRES) , two Indian Master Control Centres (INMCC) in Bengaluru and Delhi, and three Indian Land Uplink Stations (INLUS) .
- AAI has published 23 LPV approach procedures across Indian airports with plans to exceed 40 by the end of 2026, while over 250 aircraft are already equipped with GAGAN-enabled receivers.
