NISAR (NASA-ISRO Synthetic Aperture Radar Mission) is the first joint satellite mission of ISRO and NASA. It is a dual-frequency microwave imaging mission carrying L-band and S-band Synthetic Aperture Radar (SAR), with the capability to acquire fully polarimetric and interferometric data. The mission is designed to image the global land and ice-covered surfaces, including islands, sea ice and selected oceans, at a 12-day interval.
NISAR was launched onboard GSLV-F16 from the Satish Dhawan Space Centre (SDSC SHAR), Sriharikota on July 30, 2025 at 1740 hrs IST. ISRO stated that the launch vehicle would inject the satellite into a 743 km Sun-synchronous orbit with an inclination of 98.40°, while the broader mission configuration mentions a 747 km circular Sun-synchronous polar orbit (6 PM) with an inclination of 98.405°. On November 28, 2025, it was stated that GSLV-F16 delivered NISAR to orbit, with all mission stages and cryogenic stage performance described as flawless.
The primary objective of NISAR is to study land and ice deformation, land ecosystems, and oceanic regions in areas of common interest to the Indian and US science communities. The mission is intended to help scientists understand the changes taking place on Planet Earth through the combined use of S-band and L-band SAR data from a single platform.
NISAR will help measure woody biomass and its changes, track changes in the extent of active crops, and understand changes in wetland extent. It will also map Greenland and Antarctica’s ice sheets, study the dynamics of sea ice and mountain glaciers, and characterize land surface deformation related to seismicity, volcanism, landslides, subsidence, and uplift associated with changes in subsurface aquifers and hydrocarbon reservoirs. Further applications mentioned include ground deformation, ice sheet movement, vegetation dynamics, sea ice classification, ship detection, shoreline monitoring, storm characterization, changes in soil moisture, mapping and monitoring of surface water resources, and disaster response.
The unique dual-band SAR system of NISAR uses the advanced SweepSAR technique, which provides high resolution and large swath imagery. The satellite is described as the first satellite to observe Earth with a dual-frequency SAR, using NASA’s L-band and ISRO’s S-band, both operating through NASA’s 12 m unfurlable mesh reflector antenna. The mission provides an observable swath of about 240–242 km with 5–100 m resolution. It follows a free and open data policy.
The spacecraft is built around ISRO’s I-3K structure and has a lift-off mass of about 2400 kg, with one reference specifically mentioning 2392 kg. It is a 70V bus, 3-axis stabilized spacecraft. It carries two major payloads, namely the L-band SAR and S-band SAR. The satellite uses a large 12 m diameter common unfurlable reflector antenna mounted on a deployable 9 m boom.
The S-band radar system, data handling and high-speed downlink system, the spacecraft, and the launch system were developed by ISRO. The L-band radar system, high-speed downlink system, solid-state recorder, GPS receiver, and the 9 m boom carrying the 12 m reflector were delivered by NASA. ISRO is responsible for satellite commanding and operations, while NASA provides the orbit maneuver plan and RADAR operations plan. Ground station support for downloading acquired images is provided by both ISRO and NASA, after which the processed data are disseminated to the user community.
The complex payloads and mainframe systems of NISAR were designed, developed, qualified and realised over a period of 8 to 10 years. The S-band SAR and L-band SAR were independently developed, integrated and tested at ISRO and JPL/NASA respectively. The Integrated Radar Instrument Structure (IRIS), consisting of both the S-band and L-band SAR and other payload elements, was integrated and tested at JPL/NASA and then delivered to ISRO. The mainframe satellite elements and payloads were later assembled, integrated and tested at URSC/ISRO.
The NISAR mission phases are broadly classified into Launch Phase, Deployment Phase, Commissioning Phase, and Science Operations Phase. During the Deployment Phase, the satellite’s large 12 m reflector is deployed in orbit through a complex multi-stage deployable boom designed and developed by JPL/NASA. During the Commissioning Phase, the first 90 days after launch are dedicated to In-Orbit Checkout (IOC), including initial checks, calibrations of mainframe elements, and JPL engineering payload and instrument checkout. The Science Operations Phase begins after commissioning and continues until the end of mission life, with regular orbit maintenance maneuvers, calibration and validation activities, and a coordinated observation plan for both radar systems.
After the successful launch of NISAR, the 12 m diameter antenna reflector was successfully deployed. The antenna was launched in a stowed condition on a 9 m boom tucked close to the satellite. The unfolding of the boom joints began on August 09, 2025 and continued over five days, covering wrist, shoulder, elbow and root deployments. The reflector assembly mounted at the end of the boom was successfully deployed on August 15, 2025, and the performance of the antenna systems was described as satisfactory. These operations were carried out from ISTRAC, ISRO, with support from JPL/NASA.
Since the first acquisition on 19 August 2025, the NISAR S-band SAR has been regularly imaging over the Indian landmass and global calibration-validation sites in various operating configurations. For calibration, corner reflectors were deployed around Ahmedabad, Gujarat, and a few more locations in India. Data acquired over the Amazon rainforests were also used to calibrate spacecraft pointing and images. Based on these observations, the payload data acquisition parameters were fine-tuned, resulting in high-quality images.
The first S-band SAR image, acquired on 19 August 2025, captured the fertile Godavari River Delta in Andhra Pradesh. The image clearly showed various vegetation and land-use classes such as mangroves, agriculture, arecanut plantations, and aquaculture fields. This highlighted NISAR’s S-band SAR capability to map river deltas and agricultural landscapes with precision. On the 100th day of NISAR in orbit, the S-SAR images were released to the public by the Chairman, ISRO/Secretary, DOS, and the commencement of the science phase was officially announced.
According to the ISRO chief, NISAR was to be declared operational on November 7, 2025 after the completion of data calibration. It was stated that the satellite has the ability to monitor most of the planet’s land and ice surfaces twice every 12 days. The data were described as outstanding, and the satellite was considered highly useful.
The mission life of NISAR is 5 years. It is a major Earth observation mission because it combines two SAR systems of different wavelengths on a single satellite platform. The mission is expected to generate critical data for studying Earth’s changing surface and environment, while also demonstrating strong long-term technical cooperation between ISRO and NASA/JPL extending over more than a decade.
A later example of NISAR’s capability was an image of Mount St. Helens in the United States, captured on November 10, 2025 and reported later. This image demonstrated the ability of L-band SAR to observe the Earth’s surface through clouds. Surface features were represented in different colours: magenta for strong reflection from flat surfaces like roads and buildings, yellow for landform, moisture and structural effects, yellow-green for vegetation such as forests and wetlands, and dark blue for relatively smooth surfaces like water bodies or barren mountaintops. Purple square patches with straight edges indicated likely man-made landscape changes, such as deforestation or regrowth in previously cleared areas.
NISAR is a landmark joint Earth observation mission of NASA and ISRO, combining L-band and S-band SAR imaging on a single platform. Its all-weather, day-and-night, 12-day repeat global observation capability, advanced SweepSAR technology, large 12 m reflector antenna, and broad scientific applications make it one of the most significant satellite missions for monitoring the changing Earth system.