Source : INDIA TODAY NEWS
On the afternoon of June 27, 2026, an IndiGo Airbus A320 dropped gently towards the runway at Udaipur. From a window seat, nothing looked unusual.
Yet the aircraft was not being guided down by the ground-based radio beams that line most big-city runways.
It was being talked down by satellites parked thousands of kilometres above India.
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Under the watch of the Directorate General of Civil Aviation (DGCA), it became the first jet in India to land using Gagan, the country’s own homegrown navigation system, media reports said.
Small turboprop planes had managed it before. A passenger jet never had.
A turboprop is a smaller, slower aircraft powered by a propeller that is spun by a jet engine, the kind used on short regional routes, such as IndiGo’s ATR fleet, rather than the larger jets like the A320 that fly busier sectors.
WHAT IS GAGAN, AND WHO BUILT IT?
Gagan stands for GPS Aided GEO Augmented Navigation. It was built jointly by the Indian Space Research Organisation (Isro) and the Airports Authority of India (AAI).
The Gagan Signal-In-Space (SIS) is available through Isro’s GSAT-8 and GSAT-10.
It is not a fleet of navigation satellites like GPS. Think of it instead as a helper that sits on top of GPS and quietly checks its homework, correcting the mistakes before they reach the pilot.
It is easy to mix Gagan up with NavIC, the other Indian navigation system in the news, but the two do opposite jobs.
NavIC, short for Navigation with Indian Constellation, is a standalone positioning network that finds your location on its own, much like GPS.
Gagan does not navigate by itself at all. It exists only to sharpen and police the signals that GPS is already sending.
WHY IS LANDING A PLANE WITH GPS SO HARD?
The GPS in your phone is usually accurate to a few metres.
That is fine for finding a coffee shop. It is nowhere near sharp enough to bring a 70-tonne jet down through clouds.
As GPS signals travel to Earth, they are slowed and bent by the ionosphere, an electrically charged layer of the upper atmosphere.
Over India, which sits beneath a restless band called the equatorial ionisation anomaly, those errors are unusually large and shift from minute to minute.
HOW DOES GAGAN FIX GPS ERRORS?
A network of 15 ground stations across India, whose exact positions are known to the centimetre, constantly compares where GPS thinks they are with where they truly are. That gap is the error.
A control centre calculates the correction, beams it up to satellites hovering over the equator, and those satellites broadcast it straight back down to the aircraft.
According to Isro, the Gagan signal currently reaches aircraft through two communication satellites, GSAT-8 and GSAT-10, both holding a fixed spot high above the equator, so they always have India in view.
The plane’s receiver applies the fix.
Just as importantly, it is told how much to trust the answer, and if the signal cannot be trusted, the system warns the pilot within seconds.
WHY DOES THE UDAIPUR LANDING MATTER?
The flight flew what is called an LPV approach, short for Localiser Performance with Vertical Guidance.
In plain language, it hands the pilot both left-right and up-down guidance to the runway, much like the costly ground-based Instrument Landing System (ILS), but without a single piece of equipment at the airport itself.
That is the real prize. Fitting ILS into every small airport is expensive. Gagan offers the same precise, ILS-style descent using a system that already exists in orbit.
Isro lists two main aims for Gagan. The first is to give civil aviation the accuracy and integrity it needs, integrity being the promise that the system can be trusted, or will flag the instant it cannot.
The second is smoother air traffic management over Indian skies, letting planes fly more direct routes. It is also designed to work alongside similar systems abroad, so an aircraft can cross national borders without losing guidance.
For a country building regional airports at speed, that means safer landings in poor weather, fewer diversions and lower costs. India is one of only a handful of nations with such a system, and the only one proven over the difficult equatorial sky.
– Ends
SOURCE :- TIMES OF INDIA
