Determination of Optical Properties by Inversion of Multiple Scattering Data: Analytical Program

摘要

An experimental and analytical study to test the effectiveness of a time-dependent inverse radiative transfer algorithm for estimating the single scattering properties of optically-thick media was investigated. The inversion algorithm requires measurements of the time resolved backscattered radiances following a pulsed illumination of an optically-thick atmosphere. The project consisted of three components: a) further analytical development of the algorithm to numerically test the sensitivity of the estimated scattering properties to errors caused by its application in circumstances where it is less accurate or to inaccuracies in the experimental measurements, b) radiative transfer calculations to simulate the experiments, and c) application of the algorithm to results from experiments to test its viability in practice. To model the atmosphere, most of the measurements were accomplished with 532 nm, 35 ps duration pulses from a frequency doubled, passively mode locked Nd: YAG laser and a 10 ps resolution streak camera. Estimates of the single scatter albedo of weakly absorbing particles were obtained with a relative error of less than 1%. Estimates of the scattering asymmetry factor were found to be unreliable when particle diameters were much less than the wavelength of the scattered light, but relative errors of only a few percent were achieved when particle diameters were comparable to or larger than the wavelength. (jhd)