Exploring Earth Like Never Before: The Revolutionary NISAR Satellite from NASA and India

This data can assist in identifying the existence of an object or surface, its distance, and its velocity, though the resolution remains too low to create a distinct image. Initially imagined at Goodyear Aircraft Corp. in 1952, SAR addresses this challenge.

“It’s a method to produce high-resolution images from a low-resolution apparatus,” stated Paul Rosen, NISAR’s project scientist at JPL.

As the radar moves, its antenna perpetually sends out microwaves while detecting echoes from the ground. Due to the instrument’s motion in relation to Earth, there are minor variations in frequency in the returning signals. This phenomenon, known as the Doppler shift, causes a siren’s tone to rise as an emergency vehicle approaches and then fall as it moves away.

The processing of these signals by a computer resembles a camera lens that redirects and focuses light to yield a crisp photograph. With SAR, the spacecraft’s trajectory acts as the “lens,” and the processing compensates for the Doppler shifts, enabling the echoes to be combined into a singular, clear image.

Employing SAR

One form of SAR-based visualization is an interferogram, a mix of two images captured at different times, revealing the variances by assessing changes in echo delays. Although they may resemble abstract art to an untrained observer, the multicolored concentric bands in interferograms depict how much land surfaces have shifted: The closer the bands, the greater the movement. Seismologists utilize these visualizations to assess land deformation caused by earthquakes.

Another variant of SAR analysis, known as polarimetry, gauges the vertical or horizontal alignment of returning waves compared to that of transmitted signals. Waves reflecting off linear structures like edifices generally return in a similar orientation, whereas those reflecting from irregular features, such as tree canopies, return differently. By charting the differences and intensities of the return signals, researchers can discern an area’s land cover, which is valuable for examining deforestation and flooding.

Such analyses exemplify how NISAR will assist researchers in gaining deeper insights into processes that impact billions of individuals.

“This mission encompasses a broad spectrum of science directed toward a unified objective of examining our evolving planet and the consequences of natural hazards,” remarked Deepak Putrevu, co-leader of the ISRO science team at the Space Applications Centre in Ahmedabad, India.

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