A method of image reconstruction for snow search radar using an estimated permittivity of snow

For the image reconstruction of the snow search radar based on the principle of multifrequency holography method, the values of the relative permittivity of snow to be interrogated are needed. Since the relative permittivity of snow changes by various factors, it was necessary to measure it by some means at the same time as the search. The relative permittivity of the snow with low water content which is the medium of the snow search radar has a strong correlation with the density of the snow. Hence, the relative permittivity was estimated by measurement of the density in the past. To eliminate such a procedure, it is necessary to estimate the relative permittivity of the snow from the multifrequency hologram which comprises the data obtained by the snow search radar. In the multifrequency hologram, the information along the frequency axis and that on the azimuth axis are recorded independently. In addition, the distance information in each axis varies in the direction opposite to that of the change of relative permittivity. This property was used for automatically estimating the relative permittivity of snow by discriminating the focusing of the reconstructed image. In this paper, a method is presented for estimating the relative permittivity of snow from the data of the snow search radar. The results are given for processing of actual data.