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India and the United States are set to launch one of the most advanced Earth observation satellites ever built. The NASA-ISRO Synthetic Aperture Radar (NISAR) mission will lift off on July 30, marking a new chapter in Indo-US space collaboration, 50 years after the landmark SITE project.
NISAR will scan the planet every 12 days, detecting changes as small as a few centimetres across land, ice, water, and vegetation. Each pixel of its radar image will represent an area about half the size of a tennis court. The data will be freely available to scientists and used to predict floods, monitor coastal erosion, assess crop loss, and respond quickly to disasters. It will also support ship tracking and improve forest mapping.
This is the first satellite jointly developed by NASA and ISRO. The US agency has provided the L-band radar, while ISRO has contributed the S-band radar and will handle the launch from Indian soil. The combination of L- and S-band radars gives NISAR the unique ability to capture both surface detail and sub-surface changes, day or night, even through cloud cover.
“Using SAR, we can measure ground displacement down to even millimetre precision,” NASA-JPL project scientist Paul Rosen told Times of India. “It lets us read Earth’s surface like a series of moving frames.”
A leap from SITE to NISAR
NISAR’s launch comes exactly 50 years after another significant India-US collaboration—the Satellite Instructional Television Experiment (SITE). In 1975, SITE began beaming educational programming to 2,400 villages across six Indian states using NASA’s ATS-6 satellite. Launched just weeks after Prime Minister Indira Gandhi declared the Emergency, SITE reached nearly two lakh people, trained 50,000 science teachers, and delivered practical advice to farmers. It was dubbed “the largest sociological experiment in the world.”
“Fifty years ago, we used a NASA satellite to beam educational programmes,” said former ISRO deputy director Arup Dasgupta, who was involved in SITE. “Today, we are launching their payload along with our own Synthetic Aperture Radar on an Indian launcher.”
Precision tool for a shifting planet
NISAR will observe everything from Himalayan glaciers and glacial lakes to the farms of Punjab and the beaches of California. Its radar will help track the evolution of glacial lakes and improve understanding of GLOF (glacial lake outburst flood) risks, an increasingly urgent concern in the Himalayas.
“We’ve never had such a tool for studying Himalayan snow, glaciers and lake systems,” said Prof PG Diwakar of the National Institute of Advanced Studies. He also noted the L-band radar’s capability to penetrate forest canopies and assess biomass, making it invaluable for conservation work.
“A dual-band SAR like this has never flown before,” he said. “L-band opens up deeper imaging and new interferometric applications. You can track deformation, subsidence, and seismic shifts in much finer detail.”
In disaster-prone areas, the satellite’s interferometric accuracy will aid early detection of ground shifts. It can also assist in monitoring oil spills and other environmental hazards.
A legacy decades in the making
NISAR traces its lineage to Seasat, NASA’s 1978 satellite that was the world’s first to carry a spaceborne SAR. Though it operated for just 105 days, Seasat’s legacy transformed Earth observation science. Nearly five decades later, NISAR will continue that work for at least three years, beaming down more data each day than any previous remote-sensing satellite.
“This will be the first mission between US and India to observe Earth in such a detailed way,” said Nicola Fox, associate administrator at NASA’s science mission directorate.
For India, which will lead the launch, NISAR strengthens its global scientific profile. For NASA, it extends a legacy of innovation in Earth science. Together, the agencies have built a satellite that doesn’t just take snapshots—but watches the Earth evolve in real time.
