BT Explainer: Why NISAR's 'hummingbird' image from Antarctica is more than just a stunning space photograph

A striking image captured by the NASA-ISRO Synthetic Aperture Radar (NISAR) satellite has captivated scientists and space enthusiasts around the world. The radar image, which appears to show a giant hummingbird with outstretched wings across Antarctica's frozen landscape, is not a real bird but a remarkable example of how advanced radar technology can reveal hidden features of Earth's surface that are invisible to conventional satellites.

The image was produced using data collected by NISAR's L-band radar over East Antarctica. At its centre is Nunatak Zaterjavshijsja, a rocky mountain peak that protrudes through the continent's vast ice sheet. As glaciers slowly move northeast towards the ocean, the mountain acts as an obstacle, creating immense stress on the flowing ice. This pressure fractures the surrounding ice into deep cracks known as crevasses, which form a pattern resembling the outline of a hummingbird when viewed through radar imagery.

How is NISAR different from conventional satellites?

Unlike optical satellites that rely on sunlight and capture images in visible light, NISAR uses Synthetic Aperture Radar (SAR). It transmits microwave radar signals towards Earth and analyses the signals that bounce back after striking the surface. Because radar waves can penetrate clouds, darkness and even parts of snow and ice, NISAR can observe regions that are often difficult or impossible to monitor using traditional imaging satellites.

This makes the satellite especially valuable for studying remote environments like Antarctica, where prolonged darkness, cloud cover and harsh weather frequently limit optical observations.

What do the colours reveal?

The vibrant colours in the image are generated from radar data rather than natural light. Areas shown in magenta represent relatively smooth ice surfaces that reflect the radar signal back with horizontal polarisation. Green highlights rougher surfaces, particularly the walls of crevasses, where the radar waves scatter in multiple directions and return with vertical polarisation. White indicates areas where both types of signals are strong, suggesting a combination of smooth surface reflections and complex internal ice structures. These differences help scientists understand the physical characteristics of glaciers in far greater detail than visible-light images alone can provide.

Why does it matter?

The image is more than a visual curiosity. It showcases NISAR's ability to monitor glacier movement, detect changes in ice-sheet stability and improve understanding of how climate change is affecting Antarctica. Since melting Antarctic ice is a major contributor to global sea-level rise, continuous observations can help scientists improve climate models and forecast future environmental changes. The satellite will also support studies of earthquakes, landslides, forests, wetlands and land deformation across the globe.

Jointly developed by NASA and the Indian Space Research Organisation (ISRO), NISAR is the world's first Earth observation mission to carry two Synthetic Aperture Radar instruments operating at different wavelengths—NASA's L-band radar and ISRO's S-band radar. The spacecraft also carries a 12-metre (39-foot) radar reflector, the largest radar antenna reflector ever launched by NASA. With the mission now releasing data for researchers worldwide, scientists expect NISAR to become one of the most important tools for tracking changes to Earth's land, ice and ecosystems over the coming years.