On the shape of reflecting surfaces investigated by a 60 MHz radar

Radio echo sounding (RES) systems for ice thickness measurements are practically the only suitable equipment for large-scale radar flight surveys in polar regions. The length of the radio wave carrier does not allow the
employment of sophisticated antennas, so folded dipoles are used, arranged beneath the wings. As a consequence, the transmitted radio wave beam illuminates a relatively large area, making the power of the echo signal related in a significant way to the shape of the reflecting surfaces. An electromagnetic analysis shows that the amplitude variations detected by the system, under certain conditions, are mainly due to focusing or defocusing effects determined by the shape of the reflectors.