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

The authors developed an ultra-wideband radar operating over the frequencies from 2 to 18 GHz. They used this system in conjunction with a plane-wave illuminator to perform radar scattering measurements over bare and snow-covered saline ice. They made these measurements over saline ice grown in an outdoor pond at the U.S. Army Cold Regions Research and Engineering Laboratory, Hanover, NH. They collected radar data over incidence angles from 0/spl deg/ to 50/spl deg/ in conjunction with measurements of surface roughness, snow properties and ice structure. The combination of wide bandwidth and plane-wave illumination allowed them uniquely to identify returns from air-snow and snow-ice interfaces. They found that the snow-ice returns were at about 10 dB higher than those from the air-snow interface. The results also show that scattering from bare saline ice is dominated by ice surface at frequencies lower than about 10 GHz and incidence angles less than about 30/spl deg/. They also determined angular and spectral responses for smooth bare, snow-covered and pancake ice. For pancake ice the scattering coefficient at 30/spl deg/ increased from -22 at 2 GHz to about -10 at 15 GHz. Over incidence angles from 0/spl deg/ to 30/spl deg/ at 5.5 GHz, the scattering coefficient decreased by about 30 dB for pancake ice, and by about 45 dB for bare and snow-covered ice. They also compared data from laboratory observations with field measurement made during the International Arctic Ocean Experiment in 1991. For pancake ice the average scattering coefficient from laboratory observations is within 1 dB of field observations. This shows that simulation of pancake ice in the laboratory is successful.