Geophysical subsurface probing with radio-frequency interferometry

The radio-frequency interferometry method can be used to probe interiors of celestial bodies and terrestrial areas with low conductivity. Several glaciers have been studied with this technique. An experiment based on this method was designed for Apollo 17 to examine the lunar subsurface. In order to interpret the interference patterns, We have studied theoretically the electromagnetic fields due to a dipole antenna on the surface of a horizontally stratified -layered medium. Three approaches are used to calculate the interference patterns: 1 ) direct numerical integration; 2) asymptotic evaluation by the saddle point method; and 3) residue series approach. The asymptotic approach leads to the geometrical optics interpretation. The residue approach leads to modal analysis. Validity of the formulation is checked by comparisons with analogue model tank experiments and actual field data obtained from glaciers.