Radar contrast polarization dependence on subsurface sensing

Planar homogeneous layers with rough boundaries often are used as a model of sea ice, glaciers, the upper soil, and other natural layered structures for interpreting the results of remote sensing using very high frequency (VHF) radio waves. In the framework of small perturbation theory (sloping surface roughness with low heights compared with radio wavelength), the surface backscattering (radar) specific cross section (SCS) from a layered media with a rough upper boundary has been calculated. The radar contrast (RC) was introduced as the ratio of the SCS of a layered medium to the SCS of a homogeneous medium. It was shown that the RC of buried interfaces between the two media is an oscillating function of the probing signal frequency, the angle of incidence, and the layer thickness. The RC does not depend on surface roughness and, after averaging these oscillations, it increases with increasing radio wavelength and the dielectric permeability of a layer substance, and decreases with increasing layer thickness (or the depth of object burying) and soil conductivity. The RC for horizontal polarization always exceeds the RC for a vertically polarized probing signal and increases with increasing angle of incidence. For the Brewster angle of incidence, the RC for a vertically polarized probing signal has a minimal value and becomes equal to zero for unabsorbed media, although in this case all energy of the incident wave penetrates into the layer and does not reflect at all into the upper half-space for zero approximation (for a smooth upper boundary). For both polarizations, the RC was investigated numerically for two different media, dry sand and humid clay, as a function of frequency and layer thickness, and it was shown that the RC can have a value of several decibels even for objects buried in dry sand at a depth of several tens of meters