Evaluation of equivalent spheres for use in modeling nonspherical aerosol modulation transfer functions

摘要

Abstract: This paper evaluates equivalent sphere approaches for modeling nonspherical aerosols in MTFs calculations. A Monte Carlo simulation is used to calculate the image of point source in a scattering medium. The MTF is then found using a 2-D FFT on the resulting image (power distribution). The aerosol phase functions are computed using Mie theory for spherical particles and the Method of Extended Boundary Conditions for nonspherical particles. Spheres with radii determined by the nonspherical aerosol volume, surface area, orientation averaged radius, semi- minor axis length, and semi-major axis length are considered. Sample MTF results are presented for a 2:1 axial ratio prolate spheroid at a wavelength of 9.2 $mu@m. !19