ISSN 2070-7401 (Print), ISSN 2411-0280 (Online)
Sovremennye problemy distantsionnogo zondirovaniya Zemli iz kosmosa
CURRENT PROBLEMS IN REMOTE SENSING OF THE EARTH FROM SPACE

  

Sovremennye problemy distantsionnogo zondirovaniya Zemli iz kosmosa, 2020, Vol. 17, No. 4, pp. 38-48

Method and results of passive measurement of the specular component of snow cover reflection in millimeter wave range

V.A. Golunov 1 
1 Kotelnikov Institute of Radio Engineering and Electronics RAS, Fryazino Branch, Fryazino, Moscow Region, Russia
Accepted: 21.07.2020
DOI: 10.21046/2070-7401-2020-17-4-38-48
A method for measuring the specular reflection from snow cover based on the contrast of the brightness temperature of the illuminating radiation in the specular direction has been developed. The method is implemented at an incidence angle of 55 using a radiometer operating at 94 GHz and receiving both vertically and horizontally polarized radiation. The contrast of the radio brightness temperatures of the illuminating radiation in the specular direction is created by successively replacing atmospheric radiation with blackbody radiation at ambient temperature. As the object under study, a fresh snow layer is used. The volume density of the snow sample is 0.177, the thickness is 0.04 m, the thermodynamic temperature is 271 K, the transverse size is 0.4 m, and the longitudinal size is 0.6 m. The sample is placed alternatively on a metal sheet, sandy soil, ceramic tile, blackbody at ambient temperature, and blackbody at liquid nitrogen temperature. Using the experimental data of measuring the specular reflection coefficient, the values of the extinction coefficient of the snow lying on the surfaces of ceramic tiles and metal sheets are calculated. The calculations are performed within the framework of two alternative models, one of which takes into account the effective refractive index of snow, and the other does not. It is shown that only within the framework of the latter model the values of the extinction coefficient do not depend on the type of underlying medium. This means that radiation at 94 GHz does not refract at the air-snow and snow-underlying environment boundaries.As the object under study, a fresh snow layer is used. The volume density of the snow sample is 0.177, the thickness is 0.04 m, the thermodynamic temperature is 271 K, the transverse size is 0.4 m, and the longitudinal size is 0.6 m. The sample is placed alternatively on a metal sheet, sandy soil, ceramic tile, blackbody at ambient temperature, and blackbody at liquid nitrogen temperature.
Using the experimental data of measuring the specular reflection coefficient, the values of the extinction coefficient of the snow lying on the surfaces of ceramic tiles and metal sheets are calculated. The calculations are performed within the framework of two alternative models, one of which takes into account the effective refractive index of snow, and the other does not. It is shown that only within the framework of the latter model the values of the extinction coefficient do not depend on the type of underlying medium. This means that radiation at 94 GHz does not refract at the air-snow and snow- underlying environment boundaries.
Keywords: snow, millimeter waves, thermal radiation, specular reflection, refraction
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