Look Angle Correction for SMAP L-Band Radiometer Using Geolocation Measurements

Abstract

Geolocation of the radiometer footprint in scanning instruments such as SMAP has been successfully demonstrated using the change in antenna temperature as the radiometer scans across land/water boundaries (coastlines). This measurement provides the distance of the footprint from the nominal coastline, but it does not provide information about the error in look angle and azimuth of the antenna boresight vector needed to correct for the geolocation error. A method for doing this is reported using fore and aft crossings of the boundary. The approach is demonstrated using the SMAP radiometer simulator and then applied to SMAP data over the west coast of Madagascar. The error estimates of 0.3 degrees for look angle and 0.15 degrees for azimuth are consistent with independent estimates.