NISAR (NASA-ISRO Synthetic Aperture Radar) Satellite

Posted 19 Aug 2025

Updated 21 Aug 2025

3 min read

Why in News?

The NISAR satellite was successfully launched from Satish Dhawan Space Centre, Sriharikota.

About NISAR satellite

NISAR is an L and S-band, global, microwave imaging mission, with capability to acquire fully polarimetric and interferometric data.

Developed jointly by ISRO and the American space agency NASA
- NASA provided the L-band radar, GPS receiver, high-rate telecom system, Solid-State Recorder, and the 12-meter deployable antenna.
- ISRO contributed the S-band radar, the spacecraft bus, the GSLV-F16 launch vehicle, and associated systems and services.
- In terms of total investment, NASA has contributed about $1.16 billion, while ISRO has pitched in with $90 million.
Weight: 2,392 kg
Launch Vehicle: ISRO's Geosynchronous Satellite Launch Vehicle (GSLV)-F16.
Orbit: Sun Synchronous Polar Orbit
- It is the first time a GSLV rocket was used to place a satellite into a 743 km Sun-Synchronous orbit (SSO).
- GSLV is typically used for placement in Geosynchronous Transfer Orbit/GTO (35 786 km).
- SSO is a polar orbit where satellites are in sync with Sun, matching earth's rotation around sun and appearing to be in the same position relative to sun.
Mission Life: 5 years

Technical Features

SweepSAR (Swept Synthetic Aperture Radar): It is a technique used in radar imaging to produce high-resolution, wide-swath images across a broad range of terrain.
Repeat Cycle: The NISAR mission will provide high-resolution data every 12 days to monitor land changes across Earth.
Dual-band Synthetic Aperture Radar (SAR):
- L-band SAR operates at 24 cm wavelength and can penetrate forest canopy, ice, and soil, useful for biomass and deformation studies.
- S-band SAR operates at 12 cm wavelength and will excel at quantifying changes such as tree canopy height and melting snowpack.
- It is world's first Earth observation satellite to integrate both L-band and S-band SAR on a single platform.
Antenna and Resolution The satellite features a large, 12-metre diameter common unfurlable reflector antenna.
- This antenna system is capable of producing images with a resolution comparable to those from a simple ground-based antenna 20 km in diameter.
Open-Data Policy: Information collected will be freely available to global scientific community benefiting developing countries.

About SAR

SAR is a type of active data collection where an instrument sends out a pulse of energy and then records the amount of that energy reflected back after it interacts with Earth.
Unlike optical imagery, which is a passive data collection technique based on emitted energy, SAR imagery is created from the reaction of an emitted pulse of energy with physical structures (like mountains, forests, and sea ice) and conditions like soil moisture.

Why is it Synthetic?

For a given wavelength, the longer the antenna, the higher the spatial resolution.
In order to get a spatial resolution of 10 m, a physical radar antenna about 4,250 m long would be needed, which is impractical.
- For this, a Synthetic Aperture Radar has been developed.
- In this concept, a sequence of acquisitions from a shorter antenna are combined to simulate a much larger antenna, thus providing higher resolution data.

Conclusion

NISAR is a powerful tool for sustainable development, disaster preparedness, and climate resilience. For India, it marks a leap in Earth observation capability, ensuring better planning, policy-making, and fulfilment of developmental goals.