Precipitation Effects for Ka-band SAR

Abstract

Space-borne Synthetic Aperture Radar (SAR) imaging is often considered to possess both day/night and all weather operational capabilities. Whereas the first argument is true since we are dealing with an active sensor; the second does not hold in cases for which the operating frequencies are above ~ 3 GHz. Indeed, the SAR performance can be significantly affected by atmospheric effects (losses), especially at unfavourable weather conditions. The principal reason for the restriction on the use of these higher frequencies can be found in clear air losses (water vapour and oxygen), cloud attenuation and attenuation due to precipitation, primarily rain. The purpose of this interim report is to review, identify and assess the major propagation effects in SAR imaging and investigate their relevance for the case of X-band and Ka-band frequencies; i.e. the intention is to explain the underlying physical background of the effects, especially the reflection and attenuation due to precipitation.