Data from the L-band radar of the U.S.-Indian NISAR (NASA-ISRO Synthetic Aperture Radar) satellite has been instrumental in generating an image of Nunatak Zaterjabshijisha, a prominent peak in East Antarctica. This mountain extends into an ice stream that flows northeast towards the ocean, creating significant stress in the ice. The resulting strain causes deep fissures known as crevasses, prominently visible as sharp green lines in the image, which was captured in August 2025 and affectionately dubbed “Hummingbird” by NISAR scientists.
The image utilizes a color-coded system to illustrate variations in how polarized microwave signals interact with the ice. NISAR transmits radar waves with horizontal polarization over Antarctica. The returned signals—whether horizontal, vertical, or a combination—provide vital information about the reflecting surfaces.
Signals returning with horizontal polarization are indicative of smooth surfaces, such as polished ice, and are represented in magenta. In contrast, vertical polarization signals suggest interactions with irregular surfaces, such as crevasse faces, due to partial refraction or scattering at various angles. This phenomenon, known as volumetric scattering, is depicted in green.
White regions in the image indicate areas where both magenta and green signals are strongly backscattered, suggesting a balanced mix of surface and volumetric scattering.
Figure A offers an annotated view of this significant image.
The NISAR project is managed by NASA’s Jet Propulsion Laboratory, affiliated with the California Institute of Technology. This collaboration encompasses the U.S. segment of the mission, which includes the satellite’s L-band SAR and antenna reflectors. The Indian Space Research Organization contributed the spacecraft bus and its S-band SAR. Notably, the NISAR satellite is pioneering in that it hosts two SAR instruments at differing wavelengths and harnesses its satellite capabilities for comprehensive data collection. The giant drum reflector, measuring 39 feet (12 meters) in diameter, is officially recognized as the largest radar antenna reflector dispatched into space by NASA.
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Source: science.nasa.gov