Selection of the optimal traces for remote measurements of the microstructure of a scattering object produced from particle images

Abstract

An urgent problem of remote monitoring of scattering particles in the lower atmosphere is the development of methods for obtaining information about the microstructure of the scattering layer from the measured backscatter signal. The main parameters of the microstructure of the surface layer of the atmosphere include the concentration and cross-sectional of particles. In lidar sensing, the main measured quantities are the backscatter coefficient and the extinction coefficient. For single-frequency lidar sounding, these coefficients can be associated with an equivalent scattering medium consisting of monodisperse particles. This makes it possible to interpret the backscatter coefficient and extinction through the microstructure of an equivalent medium. In lidar sounding, the quantity directly related to the transverse particle size is the angular size of the halo around the beam propagating in the scattering medium. On the example of a two-position probing scheme, methods for measuring the angular size of the halo around a beam that has passed through a scattering screen are considered. The diffusing screen is an opaque plane with holes whose projections are the images of particles. It is shown that if the angular size of the beam passing through the screen is doubled, then the measurement scheme will be optimal. This can be achieved either by choosing a linear magnification, according to which the images of particles on the screen are created, or by moving the screen along the probing line. The implementation of these methods makes it possible to describe the polydisperse and non-spherical particles contained in the surface layer of the atmosphere through the cross section of equivalent particles. It becomes possible to use remote methods in the problem of monitoring the surface layer of the atmosphere.