This story is part of “India Invented This?” — The Better India’s weekly trivia series that uncovers the Indian minds, ideas and innovations behind inventions that have shaped the way we live. From ingenious solutions created by scientists and engineers to technologies developed in response to some of India’s biggest challenges, each story goes beyond the invention to explore the problem it solved, the impact it created and why it still matters today.
On a foggy winter morning, a road can disappear from view within minutes. Cars slow down, headlights come on, and even familiar turns suddenly feel uncertain.
Now imagine being 700 feet above the ground, trying to land an aircraft when the runway ahead is hidden behind a thick veil of fog.
So, when the sky turns unclear, how do planes know where to land?
The answer, in part, lies in a piece of Indian technology called Drishti — a homegrown runway visibility measuring system that helps pilots and air traffic controllers know just how much of the runway can actually be seen.
And behind this technology is aerospace scientist Dr Shubha Venkatesha Iyengar, who spent more than four decades at the CSIR-National Aerospace Laboratories (NAL), working on technologies designed to make flying safer in difficult weather.
Giving runways a pair of eyes
Fog, rain, dust and smog can make the final moments of a flight particularly challenging. Pilots need to know the Runway Visual Range (RVR), essentially, how far down the runway they can see.
That is where Drishti comes in.
Developed by Dr Shubha and her NAL team, Drishti offers a homegrown solution for measuring runway visibility in fog and rain. Photograph: (Drafsplanet)
The system uses a transmitter and receiver placed about 30 metres apart. A beam of light travels between them, and the system measures how much that light is scattered or absorbed by particles in the atmosphere. From this, it calculates visibility and sends real-time information to pilots and air traffic controllers.
In dense fog, visibility can fall below 25 metres. On a clear day, it can stretch beyond 2,000 metres. Drishti is designed to measure across this wide range, giving aviation teams a clearer picture of conditions on the ground.
It may sound like a small task, but in aviation, a few metres of visibility can make a meaningful difference.
An Indian answer to an Indian problem
Before Drishti, Indian airports largely depended on imported transmissometers for runway visibility measurements. These systems were expensive and could be difficult to maintain.
Dr Shubha and her team at NAL set out to build an indigenous alternative that could withstand the weather conditions Indian airports regularly encounter.
The result was a system that was not only developed to meet international aviation standards, but was also significantly more affordable than comparable imported equipment. Its components could be serviced locally, making maintenance easier too.
Drishti measures runway visibility in real time, helping pilots and air traffic controllers navigate poor weather. Photograph: (The Times of India)
Drishti was first deployed at airports including Delhi, Kolkata and Lucknow around 2014. By early 2026, the system had been installed at more than 100 locations across India, including civilian airports and Indian Air Force bases. Delhi’s Indira Gandhi International Airport became the first Indian airport to be fully equipped with the indigenous system across all its runways.
The woman behind the technology
For Dr Shubha, this work was part of a much longer journey in science.
The youngest of nine siblings, she studied at Central College, where she topped both her BSc and MSc before going on to earn a PhD. Her father encouraged her to pursue science at a time when relatively few women entered the field.
In 1974, she joined the National Aerospace Laboratories in Bengaluru.
Over the next four decades, she worked on aviation technologies addressing some very practical problems — including fog, rain, and poor visibility that can affect aircraft operations. She eventually served as a Distinguished Scientist and headed NAL’s Airport Instrumentation division.
Her work is a reminder that some of India’s most consequential innovations are not always the ones we see.
Sometimes, innovation is simply about helping someone see a little farther.
From foggy runways to safer landings, Dr Shubha Venkatesha Iyengar’s work earned her the Padma Shri. Photograph: (The Economic Times)
With Drishti, that someone could be a pilot approaching a runway on a foggy morning, with hundreds of passengers waiting to arrive safely.
In 2026, Dr Shubha’s contribution to aerospace engineering and aviation safety was recognised with the Padma Shri. But perhaps the most fitting tribute to her work is already built into the skies above India: when visibility falls, her technology helps bring clarity back to the runway.
