A joint mission in orbit
NISAR lifted off from Satish Dhawan Space Centre in India at 12:10 GMT on July 30, 2025. The NASA–ISRO Synthetic Aperture Radar mission brings together the Indian Space Research Organisation and NASA, the space agency of the United States. Its two radar instruments were developed to observe small changes in Earth’s surface, with applications ranging from Himalayan glacier retreat to landslide-prone terrain. A roughly 240-kilometre-wide observation swath supports the mission’s global mapping programme.
After launch, ISRO chairman V Narayanan emphasised the international scientific demand for the measurements and the closer relationship between the agencies. NASA deputy associate administrator Casey Swails described the collaboration as a pathfinder. The Reuters launch report linked the mission to climate and natural-hazard monitoring. Its scientific objectives include tracking changes as small as a centimetre, alongside repeated observations of much larger areas of land and ice.
Launch checks and hardware responsibilities
The ISRO Geosynchronous Satellite Launch Vehicle carried NISAR into a Sun-synchronous polar orbit, the launcher’s first mission to that type of orbit. Ground controllers established communication about 20 minutes after liftoff and confirmed that the spacecraft was functioning as expected. At launch, the team planned a commissioning period of roughly 90 days. Engineering checks and the deployment of the large antenna reflector were still ahead of the observatory before routine scientific work could begin. The launch and the subsequent instrument checkout were separate stages of preparing the mission.
NASA’s Jet Propulsion Laboratory supplied the L-band radar, reflector, deployment boom, science-data communications hardware, GPS receivers, recorder and payload data subsystem. ISRO’s Space Applications Centre in Ahmedabad developed the S-band radar and its calibration, processing and science algorithms. U R Rao Satellite Centre in Bengaluru supplied the spacecraft bus. Vikram Sarabhai Space Centre provided the launch vehicle, while Satish Dhawan Space Centre handled launch services. Satellite operations belong to ISRO’s Telemetry Tracking and Command Network; the National Remote Sensing Centre in Hyderabad handles S-band reception, operational products and distribution.
Two radars and a large data stream
The instruments use different microwave wavelengths: approximately 25 centimetres for L-band and 10 centimetres for S-band. Each responds differently to surface features, moisture and roughness. L-band can penetrate forest canopies, while S-band is useful for observing crops and smaller vegetation. Their combined measurements cover a wider range of surface characteristics than either instrument alone. The two instruments were integrated with a modified ISRO I3K spacecraft bus and tested before ISRO transported the satellite to the launch centre in May 2025.
NASA projected that the mission would generate about 80 terabytes of data products daily during its prime mission. Processing, storage and distribution were designed around cloud computing, with access open to users. The planned science programme encompasses several distinct kinds of observation:
- land deformation and natural hazards;
- forests, wetlands and agricultural fields;
- ice sheets, glaciers and permafrost.
Turning echoes into surface measurements
Synthetic aperture radar combines measurements taken as an instrument moves along its flight path. The antenna sends microwave pulses towards Earth and records returning echoes. Those signals carry information about travel time, strength, frequency and interactions with surfaces. Movement between the spacecraft and the ground produces small frequency changes known as Doppler shifts. Computer processing accounts for these changes and combines the measurements into a focused image. This processing provides detail that a conventional radar would need a much larger physical antenna to obtain.
Interferometry and polarimetry extract different information from radar observations. An interferogram compares images acquired at different times and uses changes in the echoes’ delay to reveal displacement. Polarimetry compares the orientation of transmitted and returning waves. Regular structures and irregular vegetation can change those orientations differently, helping researchers distinguish land cover. In NASA’s explanation of the SAR technique, these methods connect the raw signals to studies of earthquakes, deforestation and flooding. They measure different properties rather than producing interchangeable pictures of the same phenomenon.
How the partnership developed
Paul Rosen, NISAR’s project scientist at JPL, first travelled to India in late 2011 to discuss an Earth-observing radar collaboration. NASA and ISRO agreed in 2014 to develop the joint mission. Its origins included NASA’s proposed DESDynI project, whose name referred to deformation, ecosystem structure and the dynamics of ice. That L-band concept followed the National Academy of Sciences’ 2007 decadal survey. ISRO was considering an S-band satellite, and the two science teams proposed combining their interests in a dual-band observatory.
Rosen connected NISAR to a longer history of radar observations from space. NASA’s Seasat mission in the 1970s produced early scientific radar images, followed by the Shuttle Imaging Radar programme and Shuttle Radar Topography Mission. Rosen analysed Seasat data during summer work at JPL as a student beginning in 1981. In a January 2025 interview, he explained that NISAR’s products would serve ecosystem, cryosphere and solid-Earth research, as well as applications such as soil-moisture and water-resource monitoring. Free cloud access was part of that planned distribution system.
Forests and wetlands
Forests retain carbon in wood, while wetlands hold carbon in organic soils. NISAR’s L-band signals can pass through leaves and branches and return information from trunks and the ground beneath. Repeated observations can reveal whether forest cover has thinned, disappeared or grown. Cloud penetration is useful in frequently overcast tropical regions where optical observations can be interrupted. NASA’s forest-science team expected the measurements to improve knowledge of terrestrial carbon sources and sinks, particularly in less dense forests vulnerable to clearing and degradation.
Wetlands contain an estimated 20–30% of the carbon in Earth’s soil while occupying around 5–8% of its land surface. Flooded soils can release methane as bacteria digest organic material; drying exposes stored carbon to oxygen and can release carbon dioxide. NISAR’s repeated observations are intended to track the extent, frequency and duration of inundation, including seasonal and annual variation. Researchers can combine those measurements with separate greenhouse-gas observations to study the carbon cycle. Radar measurements of changing inundation and independent measurements of gas releases contribute different parts of that investigation.
Ice movement in several environments
The mission’s orbit provides coverage of Antarctica’s interior, including areas closer to the South Pole than many earlier imaging-radar missions observed. L-band signals can penetrate snow to help track underlying ice movement, while S-band is more sensitive to snow moisture associated with melting. Both operate through darkness and cloud, including the long polar winter. Scientists plan to follow ice moving from central Antarctica towards the coast and examine changing conditions where ice meets the ocean. Floating ice shelves and the land-based glaciers behind them form connected parts of that system.
NISAR also supports studies of mountain glaciers and sea ice. In the Himalayas, repeated observations through cloud can help researchers follow glacial lakes and assess flood hazards. ISRO glaciologist Sushil Kumar Singh highlighted the difficulty clouds create for instruments using visible light. At both poles, radar can follow the movement and extent of sea ice. Sea ice influences exchanges of heat and moisture between ocean and atmosphere and reflects incoming sunlight. These observations concern different environments from the grounded ice sheets, although all belong to the mission’s cryosphere programme.
Water beneath and above the ground
Groundwater withdrawal can lower the water table and compact aquifers in alluvial basins, causing the land surface to sink. Prolonged compaction can permanently reduce an aquifer’s ability to recharge. NASA’s water-science plans use surface deformation as an indirect indicator of these subsurface changes. Existing measurements from wells, levelling and GPS surveys can be sparse in space and time. Repeated radar measurements across whole aquifers can help managers identify new subsidence and follow areas where sinking continues. The measured quantity is movement of the surface, interpreted alongside knowledge of the groundwater system.
NASA identified an ability to map deformation of a few millimetres monthly over broad areas at resolutions of a few tens of metres as useful for groundwater studies. Those measurements could extend monitoring into places with limited ground networks. The mission can also map water in lakes and rivers and follow flooding beneath vegetation canopies. In areas with standing vegetation, radar observations can detect small water-level changes. Flood mapping and subsidence monitoring therefore draw on different features of the returning signals and address different water-management questions.
Infrastructure screening with ground follow-up
In a November 2024 JPL presentation, research scientist Cathleen Jones explained how interferometry could help identify movement requiring closer investigation on the ground. Engineer Allen Cadden described a proposed application at Yeager Airport in Charleston, West Virginia. A major slope failure in 2015 disrupted operations and damaged the runway safety overrun area. Engineers designed a replacement wall and installed instruments within it. Cadden envisaged using NISAR to follow deformation of the wall and its surroundings, with the aim of detecting movement early enough to assess the problem and consider remediation.
Georgette Hlepas of the U.S. Army Corps of Engineers described the mission as a supplement to existing monitoring programmes. She cited an inventory of more than 700 dams and over 2,000 miles of levees, with projects serving water supply, hydropower and flood control. Large and remote sites are difficult to monitor at every point. Her proposed use of NISAR was as a screening tool: identify areas needing closer inspection or additional instruments. This was an intended application presented before launch, rather than a record of completed satellite inspections or a certified warning service.
The spacecraft and observation cycle
ISRO’s mission configuration describes an approximately 2,400-kilogram spacecraft built around an I3K structure, with a 70-volt electrical bus and three-axis stabilisation. A deployable nine-metre boom supports the common 12-metre reflector used by both radar instruments. The configuration combines an approximately 240-kilometre observable swath with product resolutions ranging from five to 100 metres. These resolution figures concern the size of features represented in different products; the mission’s measurements of small changes in position describe another property of the observations.
The planned circular science orbit is 747 kilometres high with an inclination of 98.405 degrees. ISRO lists a five-year mission life and divides operations into launch, deployment, commissioning and science phases. Initial checks, calibration and instrument checkout prepare the observatory for science. Subsequent manoeuvres maintain its orbit, while observation plans and engineering activities are coordinated to limit conflicts. The mapping programme has a 12-day repeat cycle, with observations of land and ice from the mission’s radar coverage. Calibration and validation remain part of the science operations programme after the initial engineering checkout.
Deployment and the first images
The reflector successfully unfurled on August 15, 2025, after commands were sent to the satellite. JPL described the 12-metre antenna as the largest reflector NASA had deployed in space. Its deployment put a shared component of both radar systems into its operating configuration. The operations team monitored temperature, tension and revolutions during deployment. Telemetry indicated nominal progress before controllers confirmed successful reflector deployment. The team then planned to turn on and tune the radars, acquire Earth images and continue tuning through the commissioning period. The deployment presentation placed the beginning of science operations at approximately 90 days after launch. That sequence distinguished successful deployment from the further work needed to prepare calibrated scientific observations.
NISAR’s L-band radar captured Maine’s Mount Desert Island on August 21, 2025. In the released image, dark areas represented water, green showed forest and magenta marked hard or regular surfaces such as bare ground and buildings. Bar Harbor appeared at the island’s northeastern end. NASA described the radar as resolving objects as small as about five metres, revealing narrow waterways and small islands. The colours encoded differences in radar response and land cover. They were not the colours a camera using visible light would record over the same landscape.
On August 23, L-band observations covered land around North Dakota’s Forest River, spanning Grand Forks and Walsh counties. Forests and wetlands lined the river, with farmland to its north and south. Dark agricultural plots indicated fallow fields, while lighter areas represented pasture or crops; circular patterns reflected centre-pivot irrigation. NASA released these preliminary images on September 25 and said the spacecraft had reached its operational 747-kilometre orbit in mid-September. The release then anticipated a November science phase, keeping the early imagery separate from the later routine programme.
From initial imagery to provisional products
NASA subsequently announced provisional L-band data on July 20, 2026. The products were fully calibrated but had undergone validation at a limited number of sites worldwide. NASA’s mission data information identifies the Alaska Satellite Facility Distributed Active Archive Center as the archive for publicly available NISAR data. ISRO released processed S-band products through its Bhoonidhi portal. This later release status adds a dated stage to the mission’s development: the open-access programme includes product calibration and validation, with the limited geographical extent of provisional validation retained as a qualification.
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