What is Gagan and how did it help an IndiGo jet land safely?

An IndiGo Airbus A320 made aviation history on June 27 after becoming the first passenger jet in India to land using Gagan, the country's satellite-based navigation system.

The aircraft landed at Udaipur under the supervision of the Directorate General of Civil Aviation (DGCA). Unlike conventional approaches that rely on ground-based radio equipment, the aircraft used satellite signals to guide its descent.

Although smaller turboprop aircraft had previously used the system, this marked the first time a commercial passenger jet completed such a landing in India.

What is Gagan?

Gagan, which stands for GPS Aided GEO Augmented Navigation, was jointly developed by the Indian Space Research Organisation (Isro) and the Airports Authority of India (AAI).

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The system is supported by the Gagan Signal-In-Space through Isro's GSAT-8 and GSAT-10 satellites.

Unlike GPS or NavIC, Gagan does not independently determine a location. Instead, it improves the accuracy of GPS signals by correcting errors before the information reaches the aircraft.

NavIC functions as India's independent navigation system, while Gagan acts as an additional layer that enhances existing GPS signals.

Why ordinary GPS is not enough

GPS signals used in everyday devices can have errors of several metres. While this may be acceptable for navigation on the ground, it is not precise enough for aircraft landings.

The signals are affected by the ionosphere, an electrically charged layer in the atmosphere. Over India, these disturbances can change rapidly because of the equatorial ionisation anomaly, making corrections essential for aviation.

How the system works

Gagan uses 15 precisely surveyed ground stations across the country. These stations compare the actual location with the position reported by GPS.

Any difference is treated as an error. The correction is then calculated and transmitted to satellites positioned above the equator, which relay the information back to aircraft.

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The system also provides integrity information, warning pilots if the navigation data cannot be trusted.

Why the Udaipur landing is important

The IndiGo aircraft carried out an LPV approach, providing both horizontal and vertical guidance during landing.

This approach offers guidance similar to the Instrument Landing System used at major airports, but without requiring expensive ground equipment.

For India, the successful landing demonstrates how satellite-based navigation can support safer operations, reduce costs and improve connectivity at smaller airports, especially in regions with challenging weather conditions.

FAQs:

What is Gagan?

Gagan is India's satellite-based system that improves GPS accuracy for aviation navigation.

Why is the IndiGo landing significant?

It was the first time an Airbus A320 in India landed using the Gagan navigation system.