On July 30, a historic moment in space collaboration is set to unfold at the Indian Space Research Organisation’s (ISRO) Sriharikota launch facility. Aboard a GSLV Mk-II rocket will soar the NASA-ISRO Synthetic Aperture Radar satellite—NISAR—an ambitious joint Earth observation mission between India and the United States. This marks more than just a technological milestone; it signifies a deepening of Indo-U.S. scientific ties and a shared commitment to understanding the planet through the most sophisticated Earth-monitoring tool ever launched.
NISAR is no ordinary satellite. It is a culmination of over a decade of development, engineering excellence, and international cooperation. Weighing approximately three tonnes and costing over \$1.5 billion, it stands as one of the most expensive Earth observation satellites ever created. But what truly sets NISAR apart is its powerful dual-frequency synthetic aperture radar (SAR), which will scan Earth’s surface in unprecedented detail, monitoring everything from natural disasters and climate changes to shifts in vegetation, ice sheets, and even agricultural productivity.
Unlike conventional imaging satellites that rely on visible light, NISAR’s SAR technology uses microwaves, allowing it to penetrate clouds, smoke, and vegetation to gather precise surface data under all weather conditions, day or night. The satellite will orbit Earth in a sun-synchronous polar trajectory at an altitude of 747 kilometers, ensuring consistent lighting conditions in its observational passes. This allows for uniform comparison of surface changes across time—a critical capability for long-term monitoring.
At the heart of NISAR’s capability lies its dual radar system: an L-band SAR (1.257 GHz) contributed by NASA and an S-band SAR (3.2 GHz) developed by ISRO. The L-band radar, with its longer wavelength, will be particularly effective in detecting deformations beneath forest canopies or through soil, making it ideal for tracking earthquakes, subsidence, and glacial movement.
The S-band, on the other hand, will capture finer surface-level features like crops and shallow water bodies, making it invaluable for Indian applications such as precision agriculture, disaster response, and groundwater monitoring.
One of NISAR’s defining features is its massive 12-meter-wide mesh reflector antenna, which unfurls in orbit to facilitate high-resolution scanning across a wide 240-kilometer swath. The radar’s SweepSAR design allows digital beam steering, enabling simultaneous acquisition of large areas without compromising resolution. The system promises a spatial resolution of 3 to 10 meters and vertical sensitivity at the centimeter scale—enough to detect slight ground movements that could forewarn of landslides or infrastructure failure.
NISAR’s scientific and applied objectives span six key areas: solid Earth processes, ecosystems, ice dynamics, coastal and ocean activity, disaster response, and specialized studies including infrastructure stability, oil reservoir tracking, and food security analysis.
It will provide repeated scans of the Earth’s surface every 12 days, creating a dynamic temporal record of our changing planet. This will include annual maps of aboveground biomass at a hectare-level resolution, quarterly cropland activity assessments, and high-resolution flood and drought maps.
In the context of climate change and increased vulnerability to natural hazards, the value of such data cannot be overstated. It will empower scientists to better understand geophysical and atmospheric phenomena, governments to plan urban infrastructure or respond to crises, and conservationists to monitor forest cover and biodiversity loss. During natural disasters, NISAR can be directed to generate “damage proxy maps” in under five hours, offering near real-time support to emergency responders.
The significance of NISAR also lies in its democratic data policy. All data generated by the satellite will be made freely available, usually within hours, to users worldwide. This open-access approach not only fosters scientific collaboration but also supports underserved regions with critical information that might otherwise be inaccessible.
The satellite’s global coverage will be extensive, although certain high-latitude regions above 60º may face intermittent data acquisition due to orbital constraints.
The engineering behind NISAR reflects a fine orchestration of international expertise and technological prowess. ISRO has provided the spacecraft bus—the structural backbone that manages power, data handling, and propulsion—as well as the entire S-band radar electronics, the high-rate Ka-band telecom system, and a gimballed high-gain antenna. These contributions were designed and built at the Space Applications Centre in Ahmedabad. NASA, through its Jet Propulsion Laboratory (JPL), supplied the L-band radar system, the antenna structure, a 9-meter carbon composite boom, and avionics including a high-capacity data recorder and GPS.
After assembling the radar systems at JPL, the spacecraft was integrated and underwent its final tests at ISRO’s Satellite Centre in Bengaluru. From here, it will embark on its journey aboard ISRO’s GSLV Mk-II, an indigenously developed launch vehicle capable of delivering heavy payloads into geostationary and polar orbits.
Mission operations post-launch will be jointly handled, with daily flight commands issued from ISRO’s Telemetry, Tracking and Command Network in Bengaluru. Meanwhile, NASA’s Near Earth Network will handle most of the data downlink, supported by ground stations in Alaska, Norway’s Svalbard archipelago, and Chile.
These facilities will receive an estimated three terabytes of radar data daily, which will be mirrored by India’s National Remote Sensing Centre (NRSC) for domestic processing and distribution.
Crucially, NISAR reflects a shift toward not only technological advancement but also mission-specific customisation. While the L-band radar will operate globally, ISRO has reserved routine use of the S-band radar over India, focusing on localised data needs in agriculture, forestry, and hydrology. The tailored dual-polarisation capabilities—where radar waves are transmitted and received in varying orientations—will further enable the satellite to differentiate between surface materials like snow, soil, and biomass, aiding in more accurate land cover and land use classifications.
In the broader narrative of Earth observation, NISAR is set to redefine benchmarks. It exemplifies how space-based platforms can address urgent global concerns, from melting polar ice caps and shrinking forests to groundwater depletion and earthquake forecasting. It also sets the stage for future collaborations between global space agencies, wherein the confluence of diverse expertise can yield assets far greater than the sum of their parts.
Furthermore, as geopolitical tensions increase and the global climate crisis deepens, data sovereignty and access to high-resolution Earth observation become crucial components of national security and sustainable development. NISAR, by securing guaranteed access to vital Earth data for India and providing a robust stream of open data for the global scientific community, becomes not just a scientific mission but a strategic one.
With a minimum mission lifespan of three years—extendable to at least five based on design parameters—NISAR is poised to deliver transformative insights into the Earth’s dynamic processes. As the countdown begins for its launch from Sriharikota, the world waits not just for another satellite to be hurled into space, but for a new era in understanding our planet to begin. For ISRO and NASA, and indeed for humanity, NISAR represents the powerful synergy of cooperation, curiosity, and commitment to protecting the only home we have—Earth.
Dipak Kurmi
(the writer can be reached at dipakkurmiglpltd@gmail.com)
Tuesday, August 26, 2025