NISAR: a joint Earth radar goes public

The most useful satellite of 2026 may be one that does not take photographs at all. NISAR, the NASA-ISRO Synthetic Aperture Radar satellite, was launched on 30 July 2025, and public releases of its data began in July 2026. It carries two radars: an L-band radar from NASA and an S-band radar from ISRO, mounted on a single spacecraft. Radar can see through cloud and darkness, and by comparing images taken on repeat passes, scientists can measure movements of the ground, ice, and vegetation down to centimetre scale.

That capability explains the long list of promised uses. The same data stream can track how glaciers and ice sheets flow, how forests grow or are cleared, how soil moisture changes before a harvest, and how land shifts after an earthquake or before a volcanic eruption. For a country that depends on the monsoon and faces floods, droughts, and coastal change, an open radar record is infrastructure, not just science. The joint character of the mission matters too: it is the first hardware collaboration of this scale between NASA and ISRO, with each agency contributing a radar instrument and sharing the data.

Public release is the key word. A satellite that only its builders can use is a demonstration; a satellite whose data anyone can download becomes a public good. Researchers, state agencies, and disaster managers can test the data against ground measurements and build their own tools on top of it, which is also how errors get found and corrected. The release schedule in 2026 therefore mattered more than the launch date in 2025, because it marked the point at which NISAR stopped being a mission and started being a resource.

There are limits to keep in view. Radar measures change, not causes: it can show a hillside moving or a wetland shrinking, but explaining why still needs fieldwork, weather data, and local knowledge. And data volume is itself a challenge, since frequent global radar coverage produces far more information than any single team can read. The value of NISAR will depend on whether Indian institutions build the processing, training, and archive systems to use it.