Automatic Detection of Low-Backscatter Targets in the Arctic Using Wide Swath Sentinel-1 Imagery

Abstract

Low backscatter signatures in Synthetic Aperture Radar (SAR) imagery are characteristic to surfaces that are highly smooth and specular reflective of microwave radiation. In the Arctic, these typically represent newly formed sea ice, oil spills, and localized weather phenomena such as low wind or rain cells. The operational monitoring of low backscatter targets can benefit from a stronger integration of freely available SAR imagery from Sentinel-1. We therefore propose a detection method applicable to Sentinel-1 Extra Wide-Swath (EW) SAR scenes. Using intensity values coupled with incidence angle and Noise-Equivalent Sigma Zero (NESZ) information, the image segmentation method is able to detect the low backscatter targets as one segment across sub-swaths. We use the Barents Sea as a test site due to the abundant presence of low backscatter targets with different origins, and of long-term operational monitoring services that help cross-validate our observations. Utilising a large set of scenes acquired in the Barents Sea during the freezing season (November - April), we demonstrate the potential of performing large-scale operational monitoring of local phenomena with low backscatter signatures.