Phase approximation of the Huygens-Kirchhoff method in problems of reflections of optical waves in the turbulent atmosphere

The present paper investigates the applicability of a spectral phase approximation of the Huygens-Kirchhoff method (SPAHKM) and a phase approximation of the Huygens-Kirchhoff method (PAHKM) for calculating the fluctuations of the wave scattered from a regular object in a turbulent medium. A reflected-field representation that is rigorous within the framework of a quasioptical approximation is used in the form of a Huygens-Kirchhoff integral which contains the Green’s-function product as a function of the point-source effect (the location Green’s function) in an inhomogeneous medium under conditions of direct wave propagation. For the location Green’s function and its statistical moments the integral equations have been obtained whose free terms correspond to SPAHKM and PAHKM. The first terms of the Neumann series of the given integral equations have been calculated and the applicability of SPAHKM and PAHKM for calculating weak and strong fluctuations of the reflected wave intensity has been considered.