Reflecting Sub-Ice Surfaces Observed by Radio Echo Sounding System

Abstract

The reflection coefficient (R) at the interface of two media provides information on their electromagnetic nature. If the first medium is known, e.g. air (or ice, that in a broad interval of physical conditions maintains certain propagative characteristics nearly constant), the electromagnetic properties of the second medium can be determined. Hence, the ice/seawater, ice/water and ice/rock interfaces exhibit different reflection coefficients which can be detected by means of a RES system (Tabacco et al., 1999; Tabacco et al., 2000). The length of the radio wave does not allow the employment of sophisticated antennas, and so folded dipoles are arranged beneath the wings of the aircraft. As a consequence, the transmitted radio wave beam illuminates a relatively large area, and the power of the echo signal greatly depends on the shape of the reflecting surfaces. An electromagnetic analysis shows that, in certain conditions, the variations in amplitude detected by the system are mainly due to focusing or defocusing effects determined by the shape of the reflectors (Bianchi et al., 2001; Tabacco et al., 1999).