The Nasa-Isro Synthetic Aperture Radar (Nisar) satellite, set for launch aboard Isro’s GSLV on July 30, boasts the most advanced radar system ever deployed on an Earth observation satellite.
About the size of a pickup truck, Nisar’s core innovation is its dual-frequency radar payload: an L-band radar from Nasa and an S-band radar from Isro, marking the first time two different radar frequencies operate together in space.
Nisar’s L-band system uses a 24-centimeter wavelength, while its S-band employs a 10-centimeter wavelength. These allow the satellite to detect a wide range of Earth features in unprecedented detail, from deep within forests to subtle shifts in soil moisture or glacial ice.
Each radar band offers unique advantages. The longer-wavelength L-band penetrates dense vegetation and is optimal for monitoring landscape topography and forests, while the S-band excels at tracking soil and ice features with high sensitivity, particularly in polar regions.
The mission’s technological centerpiece is a 12-meter deployable mesh reflector, the largest ever launched by Nasa, attached to a 9-meter boom. This shared antenna supports both radars, enabling simultaneous or independent operation and covering swaths over 240 kilometers wide during each pass.
Nisar leverages the innovative “SweepSAR” technique: instead of scanning from side to side like traditional radars, it rapidly transmits and receives pulses across the entire swath, capturing echoes in quick succession and processing the data in real time.
This approach provides continuous, high-resolution, wide-area mapping of Earth’s surface.
Together, the L- and S-band radars operate in fully polarimetric mode (transmitting and receiving in multiple polarisations) and produce time-series data that can detect ground movement as small as 4 millimeters per year.
Nisar will generate a staggering 80 terabytes of data products daily, all processed and distributed via the cloud for global scientific access.
This historic collaboration between Nasa and Isro enables Nisar to systematically map the planet with a spatial resolution as fine as 3 meters, revolutionising how scientists monitor earthquakes, volcanoes, glaciers, and vegetation change, and offering unparalleled insights into Earth’s dynamic systems.
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