Simulation And Experimental Verification Of Sky Background Radiation On Oblique Path

Sky background radiation refers to the luminance distribution of the scattered light formed in the atmosphere after the solar radiation is absorbed and scattered by atmospheric molecules and aerosol particles.The variation of the sky background radiation can provide support for the detection and identification of space targets,target tracking and imaging and atmospheric feature inversion.Therefore,the distribution of sky background radiation research is of great significance in aerospace,infrared imaging,guidance and aerial detection.The distribution of sky background radiation is particularly important for the accurate detection of skew visibility in the daytime.In this paper,the simulation and experimental verification of the sky background radiation over an oblique path will be carried out.It provides technical support for the accurate calculation of slanting visibility.First,thesis based on the theory of the brightness of sky background radiation,the atmospheric transmission characteristics of sky background radiation are simulated,and the scattering and absorption characteristics of atmospheric molecules and aerosols at visible bands are discussed.Based on the absorption coefficient of single spectral line and Rayleigh scattering theory provided by HITRAN database,the scattering and absorption of atmospheric molecules were simulated and analyzed,and the optical depth and transmittance of molecules were obtained.Based on the Mie scattering theory of spherical particles,the scattering and absorption characteristics of four types of aerosols,including urban aerosol,rural aerosol,oceanic aerosol and cloud drop,were simulated and analyzed,and different aerosol scattering and extinction parameters were obtained.Based on DISORT algorithm of layered medium,the radiation transmission equation is solved based on SBDART mode.The distribution characteristics of sky background radiation under different aerosol types,weather conditions and geometric positions are discussed.The distribution trend of direct solar radiation and each layer of scattered radiation is analyzed,and the influence of aerosol single scattering albedo and asymmetric factor on the results is obtained,which provides a basis for the calculation and analysis of actual atmospheric sky background radiation.Finally,the calculation and verification of the actual atmospheric sky background radiation brightness by combining the lidar with SBDART mode are presented.The scattering phase function of 2N order Legendre polynomial was used to replace the H-G phase function,and the aerosol data actually measured by lidar was used as the input parameter of SBDART mode.And then thesis used SBDART to calculate the distribution of the sky background radiation on the oblique path under the actual sunny weather conditions.At the same time,the comparison of solar direct radiation results measured by segment solar photometer shows that the two have a strong positive correlation.Coefficient of association greater than 0.9,it can ensure the reliability of the calculated sky background radiation.The results show that the distribution of the sky background radiation on the oblique path obtained by combining the lidar and SBDART mode can guarantee the accurate calculation of the slanting visibility.