| The polar oceans and seas are seasonally covered by a thin sheet of sea ice formed by the freezing of ocean surface water. For a long time, navigators, climatologists and other researchers have been interested in sea ice properties and behavior because of the role sea ice plays in predicting global warming trends and in determining navigation in polar regions.; Sea ice parameters such as thickness and age are usually extracted by using remote sensors like orbiting satellites that utilize electromagnetic waves to illuminate the surface of the ice. A portion of these waves is scattered back to the remote sensor. Using inverse models, the sea ice characteristic are inferred from the backscattered signals. In order to develop inverse models, use is made of laboratory measurements and forward electromagnetic models. In this thesis we measure the backscattered electromagnetic field from an artificially grown sea ice sheet with known physical parameters and develop a numerical model for sea ice scattering. From the measurements and model conclusions are drawn about the sources of scattering in sea ice.; The instrumentation consists of an offset parabolic reflector antenna fed with an ultra-wide-band horn antenna. The reflector is used to illuminate the surface of the ice and receive scattered returns. The advantage of this type of antenna versus other types, such as horn antennas, is the angular resolution it permits since the radiated wavefront is a plane wave over the aperture of the reflector. Also wide-band features are desirable since they give good range resolution and insight about the frequency dependence of the electromagnetic scattering from ice sheets.; A dielectric constant probe is also built to measure the in-situ sea ice complex dielectric constant for different temperatures, salinity, and depth.; The numerical model for sea ice scattering is developed using the Finite Difference Time Domain technique (FDTD). By comparing the numerical results to the measurements, we can relate the scattered signature to the physical parameters of sea ice and test approximate analytical techniques for sea ice scattering. |
