Study Of Spectral Radiation And Scattering Characteristic Of Background And Target

The radiation and scattering characteristics of target and ground plays an important role in target detecting and recognition,the design of the seeker of the guided weapons,the design and evaluation of stealth of target.The basic principle of target detection is the discrimination of its characteristic with that of the background.Moreover,the environment influences the temperature of the target,the reflected radiation of the target and the transmission of the emitted and reflected radiation to the sensor.The effect of its ambient environment is so important that it’s meaningless to study the characteristic of the target without the attention of the environment.With the usage of the remote sensing data,the atmospheric transmission and emission characteristic,the radiation and scattering characteristic of the non-Gaussian rough sea surface and the non-uniform non-Lambertian rough land surface and the scattering of background radiation on the target surface are studied in this work.As most targets’ surfaces are non-Lambertian in the visible-infrared band,the BRDF is applied to express their anisotropic reflectance.The BRDF of skin samples are obtained by its relationship with the differential scattering coefficient which can be calculated based on the scattering theory of rough surface with its spectral refractive index.An empirical or semi-empirical statistical model can be established by the optimization algorithm with the finite calculation value.The genetic algorithm(GA)is utilized to optimize the unknown parameters of the semi-empirical five-parameter BRDF model and the modeling results are in good agreement with the direct calculation resultsThe built-in atmospheric models are applied to evaluate the transmission and emission of the atmosphere in most previous studies.However,these models are either more suited to American atmosphere or the average seasonal and latitude variations.The ERA-Interim data of ECMWF are used to construct the atmospheric models of different regions of China in 4 seasons.Then these models are imported in MODTRAN 6.0 to study the transmission and emission of the atmosphere,the solar irradiance and sky radiance.The sea surface is a major background in the battlefield environment.The sea surface emissivity model proposed by Wu and Smith treats the slope distribution sea surface as Gaussian without consideration of the wind direction.Based on their model,a sea surface emissivity model for the anisotropic sea surface is presented which takes wind direction into consideration.The sea surface BRDF model proposed by Ross has an analytical form and has been widely used.The radiance characteristic in different spectral bands of the seas neighboring our country is studied with the sea surface temperature,wind speed and direction data from ERA-Interim.At the end of September and early October in 2018,the sea surface brightness distribution in the middle and long wave bands was measured continuously at the marine meteorological science experimental base in Maoming,Guangdong.The experimental data was compared with the sea surface brightness model established by theoretical data,and the error was within the acceptable range.There’re many different kinds of land covers and their radiation and scattering characteristics can be affected by many factors,it’s difficult to construct theoretical models.As remote sensing data has large space and longtime coverage,the MODIS data are utilized to study the characteristics the spectral emissivity,BRDF and albedo of four major land covers including mixed forest,grassland,cropland and barren land in China.The land surface is treated as smooth uniform Lambertian surface when modeling the reflected radiation of the ground on the target surface,combined the MODIS data,the radiance model of the rough non-uniform non-Lambertian land surface are presented.The radiation of target is composed of thermal emission and reflection of ambient environment.The geometrical model is constructed and their surface is divided into triangular facets.The invisible facets are abandoned with the aid of Open GL,which is a computer graphics library.Then the scattering radiance of targets including sea skimming missiles,aerial fixed wing aircrafts,midcourse missile and satellite are studied.The surface of complex targets is usually composed of thousands or even tens of thousands of triangular facets,and moreover radiations from the sky and ground are distributed in the entire space,serially run on CPU is time-consuming.The multi-core CPU,Intel Xeon Phi co-processor and NVIDIA GPU has developed rapidly,the calculation of scattering of background radiation on the target surface is ported on these platforms by Open MP,Open ACC and CUDA and efforts are made to optimize the implementations based the characteristic of the platform.Optical detecting is an important method for space targets detecting.Based on the STK,the trajectory and attitude of missile and the orbit of satellite are modeled.With the reports of STK and coordinate transfer,the scattering intensity of missile is evaluated.