Overexploitation of groundwater is a worrying issue across India that is causing, among other problems, land subsidence. Mining, infrastructure building, etc, in the fragile Himalayas, are also causing land subsidence and disasters are waiting to happen, as the people of Joshimath found out recently. But so far, there have been no precise measurements of the changes that are taking place to the land or ice surfaces in different geographies across India, or for that matter around the world.

The Himalayan glaciers are melting, but there are disagreements about the rate of melt and how close the day is when the rivers they feed could start to dry up. Soon, however, we may have precise measurements of these phenomena and more, made by eyes in space. Thanks to the most ambitious project in India-US space cooperation to date, the NISAR satellite.

The NASA-ISRO Synthetic Aperture Radar (NISAR)

The NASA-ISRO Synthetic Aperture Radar (NISAR), the conception of which began more than 15 years ago alongside the India-US civil nuclear deal talks and the building of a strategic partnership between the two countries, is on track to be launched in the first quarter of 2024, according to Laurie Leshin, the Director of the famed Jet Propulsion Laboratory (JPL) in Pasadena, California, and NASA’s NISAR Project Manager Phil Barela.

Leshin and Barela were in Bengaluru to catch up on the progress on NISAR at ISRO, signaling that the work on the final testing and assembly of the spacecraft is entering the final stages. Some 160 of their colleagues from JPL’s NISAR team have traveled to the U R Rao Satellite Centre over the last nine months and worked alongside their ISRO counterparts, speeding up progress on the project after it was hit by delays through 2020-21 due to the Covid pandemic.

A Multifaceted Satellite

The NISAR is a deceptively simple concept. It puts an L-band Synthetic Aperture Radar (SAR) and an S-band SAR on a single spacecraft platform that will be launched into an orbit 747 km high by a GSLV Mk II rocket. But it is also an ambitious project.

Using these sophisticated radars that can look through clouds, bad weather and even foliage, NISAR is meant to observe changes in the earth’s land and ice surfaces planet-wide, sweeping 240 km wide swathes of these surfaces twice every 12 days, making measurements of the elevation of these surfaces to a fraction of an inch and being able to detect changes down to centimeters or less by overlapping images from different sweeps.

These changes would be good enough to measure the rate of land subsidence, indicate earthquakes and volcanoes building up, the rate of glacier melt, changes in soil moisture – extremely important for farmers – and carbon content and many other phenomena.

In effect, NISAR is a climate change observing satellite, disaster monitoring satellite and agriculture-assisting satellite all rolled into one.

The NISAR project is a testament to the growing partnership between India and the United States in space exploration and scientific research. It is also a reminder of the importance of international cooperation in addressing global challenges such as climate change and natural disasters.