India’s Nasa-Isro Synthetic Aperture Radar (NISAR) mission has crossed a defining milestone, unfurling its giant radar eye in space and returning its first sharp views of the country’s changing landscape.
A new radar eye over India
Exactly 100 days after lifting off on GSLV‑F16 from Sriharikota on July 30, 2025, NISAR has transitioned from commissioning to full science operations, with its first high‑resolution S‑Band radar image showcasing the intricate Godavari River delta in Andhra Pradesh. The scene, released by ISRO, reveals mangroves, crop fields, arecanut plantations and aquaculture ponds in fine detail, underscoring the satellite’s ability to map complex coastlines and wetlands critical to India’s food security and climate resilience.
Orbiting in a 747 km sun‑synchronous polar orbit, NISAR is designed to revisit almost every land and ice surface on Earth every 12 days, detecting ground movement on the scale of centimeters to support disaster warning, ecosystem monitoring and long‑term climate studies. By combining ISRO’s S‑Band radar with NASA’s L‑Band system on a single platform, the mission delivers an unprecedented, dual‑frequency look at Earth’s surface, from forests and farms to glaciers and coastal zones.
The high‑stakes antenna deployment
At the heart of NISAR’s capability is its 12‑metre diameter radar reflector antenna, NASA’s largest deployable antenna ever flown in Earth orbit, which was launched in a tightly folded configuration on a 9‑metre boom. Following the successful insertion of NISAR into its intended orbit, engineers began a carefully choreographed deployment sequence on August 9, 2025, gradually unfolding the boom’s “wrist, shoulder, elbow and root” joints over five days to full extension.
The reflector assembly, mounted at the end of the boom, was then swung out and locked into place on August 15, 2025, completing the mechanical transformation of the spacecraft from a compact launch configuration into a wide‑aperture radar observatory. All operations were conducted from ISRO’s Telemetry, Tracking and Command Network (ISTRAC) in Bengaluru, with engineering and operational support from NASA’s Jet Propulsion Laboratory (JPL), ensuring that both the S‑Band and L‑Band radar chains met their performance targets.
From first pings to precision imaging
Just days after the antenna was commissioned, NISAR began an initial series of “data grabs” to verify how the radar instruments interacted with the deployed reflector and boom structure. The S‑Band system started imaging on August 19, 2025, capturing scenes over India and a network of international calibration sites in different instrument modes, from wide‑swath mapping to higher‑resolution spotlight observations.
Engineers used specially installed corner reflectors near Ahmedabad in Gujarat, along with scenes over the Amazon rainforest, to fine‑tune NISAR’s pointing accuracy and radiometric calibration. These targets, with well‑known scattering characteristics, allowed teams to iteratively adjust the radar parameters until the measurements converged on the required precision, yielding data quality suitable for demanding applications in agriculture, forestry, geoscience and hydrology.
Seeing through clouds, day and night
Unlike optical imaging satellites that depend on sunlight and clear skies, NISAR’s synthetic aperture radar can observe Earth’s surface at any time of day and through cloud cover, haze and light rain. This all‑weather visibility is especially important for India’s monsoon‑dominated regions and disaster‑prone river basins, where timely data on flooding, erosion and crop conditions is often obstructed by persistent cloud.
The first Godavari delta image vividly illustrates this strength, revealing the fine texture of vegetation, water channels and human land use in a single S‑Band snapshot. As the mission scales up, repeated radar passes over deltas, coasts and river plains will allow scientists to track shoreline retreat, sediment movement, subsidence and salinity intrusion, offering early warning for communities and planners.
Science agenda: from farms to glaciers
NISAR’s observing strategy is built around repeated, systematic coverage that enables change detection over days, months and years rather than isolated “one‑off” images. In agriculture, the radar can sense crop structure and moisture, supporting yield estimation, drought assessment and irrigation planning, even when fields are shrouded in monsoon clouds.
In forestry and ecology, the combination of S‑Band and L‑Band backscatter will help quantify biomass, track deforestation and degradation, and monitor the health of mangroves and other critical ecosystems. Over the Himalayas and polar regions, repeated radar passes will be used to observe glacier motion, snowpack evolution and ice‑related hazards, feeding into water‑resource planning for downstream populations and refining climate models.
Disaster alerts and climate intelligence
One of NISAR’s most consequential promises lies in its ability to measure subtle ground deformation that can precede or follow earthquakes, landslides and volcanic events. By creating radar interferograms—maps of phase differences between repeated passes—the mission can detect centimeter‑scale shifts in the ground, supporting early warnings, post‑disaster damage mapping and more accurate hazard assessments.
For floods and cyclones, frequent radar coverage over floodplains, coastal belts and urban regions will contribute to near‑real‑time inundation maps, helping agencies plan evacuations, relief logistics and infrastructure protection. Over longer timescales, NISAR’s consistent, calibrated record of land use, vegetation and ice changes is expected to become a key global dataset for tracking how the planet responds to rising temperatures and shifting weather patterns.
An Indo‑US partnership in orbit
NISAR is among the most ambitious joint missions ever attempted by ISRO and NASA, with an estimated cost of around 1.5 billion dollars shared between the partners. NASA contributed the L‑Band radar system, the 12‑metre deployable reflector and 9‑metre boom, as well as key elements of the spacecraft bus, while ISRO provided the S‑Band radar, the satellite platform, launch on GSLV‑F16 and mission operations.
The smooth deployment of the radar antenna and the quality of the early science data now stand as a proof point for this collaboration, demonstrating that complex, shared missions can be executed on time and with high technical performance. For India, NISAR strengthens its position as a frontline provider of Earth‑observation data to both domestic users and the global community, while for the United States it showcases advanced radar and deployable‑structure technology flying on a partner’s launch vehicle.
A game‑changer for Earth observation
With the antenna fully deployed, calibration campaigns yielding top‑tier imagery and systematic mapping now under way, NISAR is poised to become a cornerstone of Earth‑observation efforts in the coming decade. From river deltas like the Godavari to Himalayan glaciers and tropical forests, its dual‑frequency radar will deliver a continuous, high‑precision record of how Earth’s surface is changing under the pressures of climate and human activity.
