Ultra-wideband radar measurements over bare and snow-covered saline ice

The authors developed an ultra-wideband radar operating over frequencies from 500 MHz to 18 GHz and used it in conjunction with a plane-wave illuminator to perform radar backscatter measurements over pancake, bare and snow-covered saline ice. The ice was grown in an outdoor pond at the U.S. Army Cold Regions Research and Engineering Laboratory, Hanover, NH. Data were acquired over incidence angles from 0° to 50° with VV and HH polarizations. Data were also collected on surface roughness, snow properties and ice structure. The combination of wide bandwidth and plane-wave illumination allowed the authors uniquely to identify returns from air-snow and snow-ice interfaces. Returns from the snow-ice interface were about 10 dB higher than those from the snow-air interface. At 0° incidence scattering from bare saline ice varied little with frequency over the frequency range from 5 to 18 GHz, whereas scattering from pancake ice increased from about 16 dB at 5 GHz to 27 dB at 18 GHz. In contrast scattering from snow-covered ice decreased by about 10 dB over the same frequency range. For both bare and snow-covered saline ice, the scattering coefficient decreased by more than 40 dB with over the angular region from 0° and 30°. The rapid decay of the scattering coefficient is indicative of the presence of a coherent component near vertical and of the dominance of surface scattering over this angular region