Modeling and interpretation of ultra-wideband microwave scattering measurements of simulated sea ice

Abstract

An ultra-wideband radar and a plane-wave antenna operating over a frequency range from 500 MHz to 18 GHz were used to measure the scattering response of bare saline ice, snow-covered ice and pancake ice at the US Army Cold Regions Research and Engineering Laboratory (CRREL) during the 1994 and 1995 winter seasons. Measurements were made at incidence angles between 0/spl deg/ and 50/spl deg/ with VV polarization. To estimate the scattering coefficient as a function of frequency, the authors had to extract the wideband response of the target. They used the Thomson's Multiple Windows technique to estimate the high-resolution spectrum and to extract the wideband response of the signal. At 0/spl deg/, the scattering from bare ice stayed fairly constant with about 1- to 2-dB variation across the 2- to 18-GHz frequency range. This indicates that the coherent component dominates over this frequency range. For pancake ice, the scattering increased from 21 to 29 dB with increasing frequency, which indicates an increasing contribution from the incoherent component with increasing frequency. In contrast, the scattering from snow-covered ice decreased from 25 to 19 dB with increasing frequency, which indicates a decreasing contribution from the coherent component at the higher frequencies. At 30/spl deg/ incidence angle, the scattering increased as a function of frequency, which is an indication of dominant incoherent scattering. The angular response of the scattering coefficients obtained using the plane-wave system show that surface scattering dominates at least until 30/spl deg/ for all the ice types. The results were compared with some simple models.