Averaged Pulse-Shape Measurements of Radar Sea Return at Near-Vertical Incidence

Some average pulse-shape measurements of radar sea returns at near-vertical incidence are presented. The measurements were made at a 75-cm wavelength, from light aircrafts flying at altitudes of 2 to 2.3 km over various water surfaces. Greater knowledge of the return shapes could help the design of high-accuracy radar altimeters. It could also contribute to several areas of remote sensing. Both specular and scattered reflections were observed in all the returns, with clear distinction between the two components. Dominance by either the specular or the scattered component was observed, the first one being the more frequent. Real-time averaging was obtained by utilizing a sampling technique. This enabled a reduction of the system bandwidth to several hertz, allowing the use of low peak-power RF pulses (1 W), and low-speed chart recorders. Twenty-one recorded average returns are given, along with an interpretation of the recordings and a description of the measuring system.