Microwave Remote Sensing of Random Media Using Multiple Scattering Theory
The modified radiative transfer (MRT) theory is used to study electromagnetic wave scattering from a half -space anisotropic random medium. Microwave remote sensing is the application which is of interest here. The MRT equations are solved under the first order approximation. The scattering coefficients and the emissivities are respectively calculated for active and passive remote sensing. We identify the effects due to multiple scattering by comparing our results with those of single scattering. Several numerical data are shown in order to highlight the characteristics of our results. As an application our theoretical model is used to interpret measured passive remote sensing data of multiyear sea ice. In order to study the validity of the first-order approximation the MRT equations are reexamined. For simplicity the isotropic case is considered. We extend our first -order solutions to obtain higher-order solutions and thus express the backscattering coefficients as an infinite series. The second-order solutions are shown to be important for cross-polarized backscattering. Further, while studying the second-order scattering processes the absence of some 'phase' terms is noticed. We offer explanation for this and suggest that the present MRT equations be further modified. Next we consider a half-space random medium with a random boundary and seek a multiple scattering solution. The Dyson equation and the Bethe-Salpeter equations are derived using the Feynman diagram techniques; these equations respectively govern the mean field and the field correlation. The various scattering processes are identified with the help of the Feynman diagrams. We notice the scattering interaction between the random medium and random surfaces. As the final topic the polarimetric bistatic scattering characteristics of layered random media are investigated. First the bistatic Mueller matrix of a half-space random medium is derived. The power received by the receiving antenna is the quantity chosen to be optimized. For the case when the transmitting and the receiving antennas have identical polarizations the optimum polarizations are derived and the results show they include both linear and elliptical polarizations. Also the conditions for maximum and minimum power are obtained. As further examples the above procedure is applied to two other cases.
- Pub Date:
- ELECTROMAGNETIC WAVES;
- Physics: Radiation; Physics: Optics; Physics: General; Remote Sensing