Passive remote sensing of three-layered anisotropic random media

We have developed the theoretical model for scattering and propagation of the electromagnetic wave in three-layered anisotropic random media to study passive microwave remote sensing of earth terrain media. The dyadic Green's functions (DGF) for three-layered anisotropic media, which are assumed to be tilted uniaxial, are used with the Born approximation to calculate the bistatic scattering coefficients and the emissivities. The theoretical results are used to interpret passive remote sensing data from multi-layered random media such as multi-year sea ice. In remote sensing of earth terrain, it is known that wave scattering plays an important role in the electromagnetic response of radars in active remote sensing and of radiometers in passive remote sensing. The more realistic terrain model should partition the entire scattering medium into subregions of random media, each with different statistical property. The importance of the anisotropic random medium model in nature has been recognized by many people. To take into account both the layered structure and anisotropic property, we will study the multi-layered anisotropic random media. Based on the wave theory under the Born approximation where a single scattering process is considered and all the multiple reflections at the boundaries are considered, the bistatic scattering coefficients are first derived. By using the energy conservation and reciprocity arguments, the bistatic scattering coefficients are integrated over the upper hemisphere and are subtracted from unity in order to calculate the emissivities (e) for the random-medium layer at viewing angles (θ_oi, φ_oi) with horizontal (H) or vertical (V) polarization for application to passive microwave remote sensing. Emissivity is a very useful parameter to evaluate especially for discriminating various types of media because it is a direct measure of the radiant flux from the medium. The flux varies with electrical and physical properties which in turn depend on the type of the medium.