(GIST OF YOJANA) NISAR: Science from Orbit, impact on Earth

GIST OF YOJANA : NISAR: Science from Orbit, impact on Earth

DECEMBER-2025

NISAR: Science from Orbit, impact on Earth

Context:

NASA-ISRO SAR (NISAR) is a Low Earth Orbit (LEO) observatory launched into a Sun Synchronous Polar Orbit (SSPO) at an altitude of 747 km. NISAR has capability to map the entire globe in 12 days and provide spatially and temporally consistent data for understanding changes in Earth’s ecosystems, ice mass, vegetation biomass,sea level rise, groundwater and aid in the study of natural hazards like earthquakes, tsunamis, volcanoes and landslides.

About NISAR:

The all-weather, day-night imaging satellite carries L and S dual-band Synthetic Aperture Radar (SAR), which operates with the Sweep SAR technique to achieve a large area on ground (swath) and with high-resolution data. The SAR payloads mounted on the Integrated Radar Instrument Structure (IRIS) and the spacecraft bus are together called an observatory. The NISAR spacecraft is configured using ISRO’s I3K bus utilising the capabilities to the fullest with respect to accommodation, power generation, thermal management, etc.

Capabilities of NISAR:

Time-varying displacements over Himalayan and Antarctic cryosphere regions at 12 days interval at a scale of 100 metres,
Measure the glacier faces and wet snow coverintheHimalayanregionat12-day intervals, and sea ice drift near Indian Antarctic stations at 3 days or better,
Above-ground woody biomass of forests and its disturbance over the Indian region at the hectare scale,
Actively growing cropland and inundated areas over India,
Soil moisture at 100 m resolution over Indian regions,
In support of response to major natural or anthropogenic disasters, the mission system is capable of providing revised scheduling for new acquisitions within 24 hours of an event or an event forecast notification and delivering data within 5 hours of being collected,
Mangrove cover map of India every year at a spatial resolution of 25 m,
Sea ice characteristics over the seas surrounding India’s Antarctic polar stations at 500 m resolution at an average sampling interval of 6 days.

NISAR Integration and Test was carried out in four stages, and the major activities at each stage are given below:

Stage-1, when the L-SAR, S-SAR, and other deliverables were designed, integrated and tested in their respective countries.
During Stage-2 the two radars, the L-band Synthetic Aperture RADAR (L-SAR) and the S-band Synthetic Aperture RADAR (S-SAR) by ISRO, were mechanically and electrically integrated, and the two systems were tested together for joint operations at JPL.
The third stage provided confidence in the system performance as an Integrated Radar Instrument System (IRIS) during which the Payload Chain Systems (Radar, Data Handling, Recorder, Boom, Reflector, Data Downlink) were evaluated in the space environment.
During Stage-4 the IRIS was integrated with the spacecraft bus. The deployable 12 m reflector, solar panels and the data downlink antenna were finally assembled, preparing NISAR for launching tests.

NISAR in Orbit

NISAR was launched into the designated orbit by GSLV Mark-11 (F16) on 30 July 2025. The spacecraft had carried fuel to correct its orbit, maintain it (altitude: 727 and 767 km, 6 PM descending node, mean local time +/- 5 minutes), safeguard itself from threats and also enough to de-orbit once its life is completed. However, the initial orbit given by the launch was well within the error bounds such that NISAR life extends by several more years.

The S-SAR and L-SAR saw their first light in orbit on 21st and 22nd of August respectively. The SAR images, commonly called pepper & salt images, are not visually appreciable, but the satisfaction on the faces of the engineers who processed the data showed that the quality of the images was as expected. Subsequently, NISAR fired its thrusters to achieve the final science orbit and began the calibration of the RADARs. NISAR during its science phase will generate almost 80Tb, which will be downloaded on ground stations of both ISRO and NASA. L-SAR data is downloaded on NASA stations and S-SAR data on ISRO stations.