Sovremennye problemy distantsionnogo zondirovaniya Zemli iz kosmosa, 2021, Vol. 18, No. 3, pp. 298-306
Use of special screens simulating scattered radiation by a medium to measure the equivalent cross-section of particles
G.P. Arumov
1 , A.V. Bukharin
1 1 Space Research Institute RAS, Moscow, Russia
Accepted: 12.05.2021
DOI: 10.21046/2070-7401-2021-18-3-298-306
Three methods for measuring the equivalent cross section of scattering particles are proposed. The dependence of the angular transformation of the beam on the ratio of the unnormalized moments of the second and first orders for the particle cross sections is the basis for the first method. The use of 3D screens to measure unnormalized first and second order moments by photometry is the basis for the second method. Processing of digital imaging of particles is the basis for the third method. An intermediate equivalent screen, consisting of monodisperse specular spherical particles, can be created as a result of such measurements. This screen has the same basic coefficients (backscatter coefficient, extinction coefficient) and angular distortion of the beam as the investigated scattering object. The ratio between the backscatter and extinction coefficients for an equivalent screen can be modeled using a spherical segment and a truncated cone. With this approach, the use of methods for solving the ill-posed inverse problem is minimal, since only two microphysical parameters are applied to describe the equivalent model of a scattering object. These parameters are the equivalent cross section and concentration of equivalent scattering particles. It is noted that the method is applicable for non-spherical particles with cross-sections in the form of convex geometric figures. Different values for the equivalent cross section of the non-convex geometric figures can be measured by means of 2D and 3D screens. Such a discrepancy may indicate the presence in the scattering layer of cross sections from nonspherical particles in the form of intersecting curved lines. The proposed approach is characterized by unambiguous transitions both from the lidar dataset to the equivalent screen and from the microstructure of the scattering layer to the equivalent screen.
Keywords: backscattering coefficient, extinction coefficient, ill-posed inversion problem, unnormalized moment, cross section, non-spherical particles, equivalent screen, scattering medium, 3D screen, 2D screen
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