Geocalibrating Millimeter-wave Spaceborne Radiometers for Global-scale Cloud Retrieval

The planned EUMETSAT Polar System-Second Generation (EPS-SG) Ice Cloud Imager (ICI) radiometer will provide quantitative estimates of ice clouds and snowfall from space. ICI has 11 channels in the millimeter and sub-millimeter wave range (from 183 up to 664 GHz). These wavelengths allow to detect ice clouds, whereas the emission signal from the surface is predominantly masked by high water vapor opacity. The latter is a problem for the geolocation assessment because current methods, comparing coastlines in imagery data with the known geographic locations, are not readily applicable to ICI channels. However, in very dry atmospheric conditions the geolocation validation technique could be still based on the observations at 183.3±7 GHz. This work proposes to evaluate geolocation error over the two biggest ice shelves (Ross and Filchner-Ronne) in the Antarctic region as surface natural targets, using as a coastline reference, data derived from Sentinel-1 synthetic aperture radar (SAR) imagery.