NASA and ISRO have begun releasing data from the NISAR satellite's dual radar systems, offering researchers new insights into the movement and structure of Antarctic ice and other dynamic Earth surfaces
Researchers now have access to a new stream of data from the NASA-ISRO Synthetic Aperture Radar (NISAR) satellite, which is providing detailed radar observations of Earth's land and ice. The mission, a collaboration between NASA and the Indian Space Research Organisation (ISRO), is designed to systematically monitor changes in the planet's surface, with a particular focus on dynamic regions such as glaciers, forests, and wetlands. The first public data releases, which began on July 20, mark a significant milestone as the mission approaches its first anniversary since launch.
Dual-Band Radar and Antarctic Imaging
NISAR is equipped with two synthetic aperture radar instruments: an L-band system provided by NASA and an S-band system from ISRO. These instruments operate at different microwave wavelengths, allowing the satellite to penetrate cloud cover and, in some cases, snow and ice. In August 2025, during system testing, the L-band radar captured a striking image of Nunatak Zaterjavshijsja, a mountaintop in East Antarctica surrounded by flowing glacial ice. The processed data revealed a fractured landscape, with crevasses appearing as sharp green lines and smoother ice surfaces rendered in magenta. The resulting image, notable for its intricate structure, has been likened to the shape of a hummingbird, though this resemblance is coincidental rather than physically meaningful.
The radar's ability to distinguish between surface and subsurface features is a key advantage over optical imaging. While visible-light satellites show Antarctica as a largely uniform white expanse, NISAR's radar can detect differences in ice structure and stress, providing clues about glacier movement and the formation of crevasses. The mission's data products are expected to support research into ice dynamics, ecosystem monitoring, and natural hazard response.
Data Release and Mission Status
Since its launch from India's Satish Dhawan Space Centre on July 30, 2025, NISAR has undergone a year of calibration and algorithm refinement. The satellite now surveys nearly all land and ice-covered surfaces on Earth twice every 12 days, generating dozens of terabytes of data daily. As of July 20, the U.S. mission team has begun continuous release of calibrated L-band data collected since June 17, while the Indian team is distributing S-band data through the Bhoonidhi portal. Earlier limited releases included sample and pre-calibrated products, but the current phase marks the start of routine, large-scale data availability.
All NASA synthetic aperture radar data, including NISAR's L-band products, are hosted at the Alaska Satellite Facility Distributed Active Archive Center. The mission's coverage extends from near the South Pole to 77.5 degrees north latitude, enabling global monitoring of land deformation, ice flow, and surface changes. The dual-band approach allows for complementary observations: the L-band can penetrate vegetation and ice, while the S-band is sensitive to surface features such as forest canopies.
Interpreting the Radar Signal
The colors in NISAR's processed images correspond to the polarization of the returned radar signal. Horizontal polarization, shown as magenta, typically indicates smooth surfaces like undisturbed ice, while vertical polarization, rendered in green, is associated with volume scattering from irregular features such as crevasses. Areas where both polarizations are strong appear white, suggesting a mix of surface and subsurface scattering. This method provides a richer understanding of ice structure than optical images alone.
For comparison, an optical image of Nunatak Zaterjavshijsja taken by the Landsat 9 satellite in November 2025 shows the region as almost entirely white, with only subtle shadows hinting at underlying topography. NISAR's radar, by contrast, reveals the internal structure of the ice and the mechanical stresses imposed by the mountain. Such detailed imaging is essential for understanding how glaciers respond to obstacles and for tracking changes over time.
Mission Architecture and Scientific Context
NISAR is the first free-flying satellite to carry two synthetic aperture radar instruments at different wavelengths. The spacecraft's 12-meter-wide drum-shaped reflector is the largest radar antenna NASA has deployed in space. The U.S. component, managed by Caltech's Jet Propulsion Laboratory, provided the L-band radar and antenna, while ISRO contributed the spacecraft bus and S-band radar. The mission's design enables frequent, high-resolution mapping of Earth's surface, supporting a wide range of geophysical and environmental studies.
Recent NISAR observations have included urban grids, agricultural regions, landslides, earthquakes, and subsiding land, complementing airborne campaigns such as those described in Science Report's coverage of NASA's new airborne Earth missions. As the mission transitions into routine science operations, researchers anticipate that the growing dataset will improve models of ice flow, land deformation, and ecosystem change, though the interpretation of radar signals remains subject to calibration and environmental complexity.
Synthetic aperture radar (SAR) is a remote sensing technique that uses the motion of a spacecraft or aircraft to simulate a much larger antenna, achieving high spatial resolution. By transmitting microwave pulses and recording the returned signal, SAR instruments can image Earth's surface regardless of weather or lighting conditions. Polarization analysis-measuring the orientation of the returned signal-enables researchers to distinguish between surface types and structural features. However, interpreting SAR data requires careful calibration and an understanding of how different materials scatter radar waves, making ground validation and algorithm development essential for extracting reliable scientific information.
