Nisar: The billion-dollar radar that can see through clouds and darkness

India Today

27-07-2025

When Nisar, a.k.a the Nasa-Isro Synthetic Aperture Radar, takes flight aboard India's GSLV Mk-II rocket from the Satish Dhawan Space Centre, Sriharikota, on July 30, 2025, it won't just be another Earth observation satellite in orbit, it will be a technological marvel, the likes of which the world has never seen before.The satellite will be placed in a sun-synchronous polar orbit, 747 km above Earth, completing 14 orbits every day.advertisementIn just 97 minutes, Nisar will circle the planet once, and in 12 days, it will have mapped nearly every inch of Earth's landmass and ice sheets. For scientists, climate researchers, and disaster managers, this is a dream come true.
The mission's open-source data will be freely available to researchers. (Photo: Isro)
WHAT MAKES NISAR A GAME-CHANGER?
At its heart, Nisar carries a world-first technology – a dual-frequency Synthetic Aperture Radar (SAR). Most radar imaging satellites work with a single frequency, but Nisar carries two powerful radar systems: L-band radar (24 cm wavelength) built by Nasa and S-band radar (12 cm wavelength) developed by Isro.This unique combination allows Nisar to 'see' through clouds, thick forest canopies, smoke, and even in complete darkness.More importantly, it can detect tiny changes in the Earth's surface, as small as a few millimeters. That means scientists can track how much a glacier has shifted, how much a fault line has moved after an earthquake, or even how much a city is sinking due to groundwater depletion.
Nisar is set to become something more – a guardian that can sense Earth's heartbeat. (Photo: Nasa)
Nisar achieves this precision through a special technique called Interferometric Synthetic Aperture Radar (InSAR). Think of it like taking two radar 'photos' of the same place a few days apart and comparing them to spot tiny differences.Nisar sends out invisible radar waves to Earth's surface and listens for the waves that bounce back. By carefully analysing the timing (or 'phase') of these returning waves, InSAR can detect changes as small as a centimeter, like the ground shifting slightly after an earthquake or a glacier moving over time.advertisementThis creates detailed maps showing how Earth's surface is changing, helping scientists predict disasters or monitor climate shifts with incredible accuracy, no matter the weather or time of day.All this data is made possible thanks to its massive 12-meter gold-plated deployable mesh antenna – the largest radar imaging antenna ever launched into space. For comparison, it's almost as wide as a badminton court when fully unfolded.
WHY THE WORLD NEEDS NISAREarth's rapid changes are outpacing the capabilities of traditional satellites, which often lack the precision needed to capture critical details. Nisar bridges this gap with its high-resolution, all-weather, day-and-night imaging, delivering a near real-time view of our planet's dynamic systems.It will revolutionise our understanding by:advertisementTracking climate change: Observing polar ice loss, glacier shifts, and permafrost thawing with unprecedented accuracy.Disaster management: Identifying subtle signs of land subsidence, landslide risks, and fault-line movements to predict earthquakes early.Agriculture & water security: Forecasting crop yields, monitoring soil moisture, and mapping groundwater depletion to ensure resource sustainability.Forests & ecosystems: Measuring deforestation, forest biomass, and the carbon storage potential of vegetation to support conservation efforts.In simple terms, Nisar will give us a near-real-time 'health check-up' of the Earth every few days.
It has the largest radar imaging antenna ever launched into space. (Photo: Nasa)
A BILLION-DOLLAR PARTNERSHIPNisar is one of the most expensive Earth observation missions ever undertaken, with a total cost estimated at $1.5 billion (Rs 12,500 crore).Nasa's contribution, covering the L-band radar, radar electronics, GPS receivers, and engineering support, is approximately $1.2 billion (Rs 10,000 crore).Isro's contribution, which includes the S-band radar, satellite bus, launch vehicle, and ground systems, is around Rs 788 crore (approximately $93 million).Despite the significant investment, the mission's open-source data will be freely available to researchers and governments worldwide, offering immense value for global scientific and climate research efforts. THE ROAD AHEADFor decades, satellites have been our eyes in the sky, but Nisar is set to become something more – a guardian that can sense Earth's heartbeat.By tracking movements invisible to the naked eye, it promises to help humanity understand natural hazards, prepare for disasters, and fight climate change.advertisementWhen it finally unfurls its giant golden antenna in orbit, Nisar will mark not just a triumph of space technology but also a symbol of international cooperation for the planet's future.(This is an authored article by Manish Purohit. Manish is a solar energy and spacecraft solar panel expert with extensive experience in managing critical space missions, including Chandrayaan-2 and Mangalyaan)- EndsMust Watch