Sea Ice Transition Detection Using Incoherent Integration and Deconvolution

Abstract

Currently, reflectometry-based sea ice detection methods rely on observables extracted from delay-Doppler maps (DDM)s, which are sensitive to ice in the specular zone. Due to the size of the glistening zone, the transition from open seas to sea ice in the specular zone can take up to 10 s for satellite platforms and no methods exist that can process this. In this article, using DDMs collected by TechDemoSat-1, we demonstrate that this transition is comprised of a response that is fixed in the spatial domain, at the ice edge, and moving in the delay-Doppler domain. This is the first observation of persistent nonspecular coherent reflections from sea ice. The delay-Doppler trajectory of the ice response is shown to correspond with a point that is located on the ambiguity free line. Furthermore, the response is point-like as it suffers from delay and Doppler walk suggesting that it originates from a small spatial footprint, i.e., the first (few) Fresnel zone(s). Exploiting these facts, we then propose a technique that integrates the ice response in the spatial domain after preprocessing. This results in the edges of the ice sheet being emphasized as all of the power received during the transition phase maps to the edge of the sheet. We also propose to compensate for the delay-Doppler walk during preprocessing by modifying Woodward's ambiguity function when deconvolution is performed.