Sovremennye problemy distantsionnogo zondirovaniya Zemli iz kosmosa, 2019, Vol. 16, No. 6, pp. 221-234
Doppler spectrum of microwave signal backscattered by sea surface at small incidence angles
V.Yu. Karaev
1 , Yu.A. Titchenko
1 , E.M. Meshkov
1 , M.A. Panfilova
1 , M.S. Ryabkova
1 1 Institute of Applied Physics RAS, Nizhny Novgorod, Russia
Accepted: 15.10.2019
DOI: 10.21046/2070-7401-2019-16-6-221-234
The spectral and energy characteristics of the backscattered microwave radar signal contain information about the parameters of the scattering surface. At present, the main information parameter is the backscattering radar cross section, which is determined by the geometry of the underlying surface. The information on the movement of the sea surface is contained in the Doppler spectrum of the reflected radar signal. In this paper, we consider the properties of the Doppler spectrum at small angles of incidence, when the quasi-specular backscattering mechanism dominates. The dependences of the width and shift of Doppler spectrum on the speed and direction of the wind and the incidence angle are constructed. It is shown that even for pure wind waves there is an ambiguous relationship between wind speed and Doppler spectrum parameters, which leads to ambiguity in solving the inverse problem. Numerical estimates showed that the parameters of antenna beam have a strong effect on the width and shift of the Doppler spectrum and this effect can be used to create simpler measurement schemes and develop new retrieval algorithms, which is especially important for orbital radars.
Keywords: width and shift of the Doppler spectrum, Kirchhoff approximation, two-scale model of scattering surface, small incidence angles, wind waves, antenna beam
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