28-07-2025
In Nisar collaboration, space exploration paths converge
The Nasa-Isro Synthetic Aperture Radar (Nisar) mission will lift off on Wednesday. At first glance, it's the world's most expensive Earth observation satellite: a $1.5-billion mission, 2,800 kg observatory, carrying two different radar frequencies (L-band and S-band), capable of detecting centimetre-level surface changes globally every 12 days. A technical marvel. And notably, its data will be freely available and open to the public.
But, Nisar is more than a satellite. It represents the quiet convergence of two space philosophies — one born from the urge to explore the planets, and the other grounded in the belief that space should serve people back home. Nisar is the first mission of its kind: a dual-band Synthetic Aperture Radar (SAR) satellite that can measure Earth's changing ecosystems, dynamic surfaces, and ice masses. It will provide insights on biomass, natural hazards, sea level rise, and groundwater, and will support a host of other applications.
But, the mission didn't start that way. It began as a proposal, DesDynI, a Nasa-only mission aimed at studying hazards and global environmental change — technically ambitious, but logistically challenging. That is, until Isro joined in. A rare kind of collaboration followed. Both Isro and Nasa contributed critical components rooted in their respective space programmes. Nasa brought its L-band radar and the deployable mesh reflector, Isro built the S-band radar, added the satellite bus, and will launch it aboard a GSLV. They created something neither could have done alone — not at this scale, not with this coverage, and certainly not with this economics.
This partnership of dual-band SAR was only possible because of the long and distinct paths that led Nasa's Jet Propulsion Laboratory (JPL) and Isro's Space Applications Centre (SAC) to this moment. Nasa-JPL had explosive beginnings, literally. In the 1930s, Caltech graduate students known as the 'Suicide Squad' began testing rocket engines in the Arroyo Seco canyon near Pasadena. Their makeshift experiments occasionally caused explosions that shook the campus. But, they also laid the foundation for what would become one of the world's foremost planetary science institutions.
Nasa-JPL went on to lead landmark missions — from Magellan's radar mapping of Venus to the Cassini-Huygens mission that revealed Saturn and its moons in stunning detail, and the Shuttle Radar Topography Mission (SRTM), which redefined how we map Earth from space. Its ethos, Dare Mighty Things, reflected its relentless pursuit of interplanetary exploration.
Isro's SAC, based in Ahmedabad, grew from a different vision. SAC-Isro was built on the belief that space should serve society. In 1975, SAC led the Satellite Instructional Television Experiment (Site), broadcasting educational TV to more than 2,400 Indian villages via a Nasa satellite, a global first in using space for mass communication. Its Earth observation journey, too, began humbly — with a challenge close to home: coconut root-wilt disease in Kerala. Traditional detection was slow, prompting PR Pisharoty, the Indian physicist and meteorologist considered to be the father of remote sensing in India, to successfully use aerial infrared photography. This sowed the seeds for the Indian Remote Sensing (IRS) programme.
That spirit of innovation endured. From airborne SAR trials in the 1980s to the wake-up call of the Kargil War, SAC-Isro played a key role in shaping India's all-weather imaging capability, culminating in RISAT-1, the country's first indigenously developed radar imaging satellite. Since then, it has contributed to landmark missions like Chandrayaan and Mangalyaan, all the while staying true to its founding principle.
In 2014, following Prime Minister Narendra Modi's visit to the US, the Nisar partnership was formalised when Nasa administrator Charles Bolden and then Isro chairperson K. Radhakrishnan signed documents in Toronto to launch a joint Earth-observing satellite mission. It was a symbolic and strategic handshake between two spacefaring nations.
Nasa is providing the mission's L-band synthetic aperture radar, a high-rate communication subsystem for science data, GPS receivers, a solid-state recorder and payload data subsystem. Isro is providing the spacecraft bus, the S-band radar, the launch vehicle and associated launch services.
Nisar proves that international space partnerships can be complementary. Its model — shared costs, aligned objectives, and different expertise coming together — is a blueprint for future collaborations.
Two roads diverged in the space age, and today they converge at Nisar. It's a powerful reminder that progress doesn't always come from working in isolation. Real breakthroughs happen when diverse approaches, ecosystems, and capabilities come together with a shared purpose. Nisar signals that the future of space lies in collaboration, not competition.
Gaurav Seth is CEO and co-founder, PierSight, an Indian space tech startup, and Steffi Joseph works with PierSight. The views expressed are personal.
