【作者】 杨春平；

【导师】 吴健；

【作者基本信息】 电子科技大学 ， 光学， 2008， 博士

【摘要】 天空背景光谱辐射特性及其场景仿真是地面对空中目标探测、地对空遥感等领域的研究热点。地对空光学探测系统在工作时，观测系统除了接收到目标自身的辐射和目标对太阳辐射的散射辐射外，还包括大气分子、气溶胶以及云等微粒对太阳辐射的散射辐射、大气自身的热辐射以及太阳的直接辐射等，它们构成了地对空观测时的背景辐射。对于观察系统而言，能否从复杂的背景中区分出目标的关键之一在于目标与背景的光谱辐射亮度之间的对比度，因此天空背景光谱辐射亮度分布是对空监视、空中目标搜索及跟踪等应用必须考虑的基本数据。本文正是针对上述问题，对天空背景光谱辐射特性的计算方法和数值场景生成的方法作了创新性和探索性研究，为探测系统仿真提供了基础依据。本文的主要研究内容和结果为：1．分析了大气分子和气溶胶微粒的消光参数垂直廓线数据库的构建方法；研究了大气分子、气溶胶等的散射象函数，分析了不同情形下散射象函数的表述形式；2．研究了无云大气情形下天空背景辐射亮度的近似计算方法；基于输运理论，研究了辐射传输方程的建立过程；对辐射传输方程的通用解法进行了分析，介绍了求解多层介质辐射传输方程的修正Eddington近似法和离散坐标法，给出了计算实例。计算结果表明：与利用离散坐标法的计算结果相比，利用修正Eddington近似法计算多次散射的贡献具有足够的精度，而且计算速度更快；3．研究了典型水云和冰云消光参数的近似计算方法，计算结果表明：利用本文提出的近似法计算值与利用Mie理论计算出的结果符合较好；提出了典型云对天空背景辐射亮度影响的计算方法；4．从能量守恒定律出发，建立了朗伯地表对下行辐射的反射作用引起天空背景辐射亮度的解析计算模型。利用射线追踪原理，提出了地表与大气之间单次反射、多次反射影响天空光谱辐射亮度的计算方法。计算结果表明：随着地表反射率的增加，地表反射对天空背景辐射亮度的影响也随之增强，同时在观察方向靠近地平线时，这种影响急剧增加，即存在明显的“临边增亮”效应；5．分析了天空背景场景的数值仿真方法，同时利用辐射传输理论和分形理论对云场景仿真方法进行了研究，开发了天空背景辐射亮度计算和场景生成软件以及与目标背景合成场景的接口程序，软件中包括有云状态时的仿真程序。更多还原

【Abstract】 While a spatial object is observed by a ground detection system,besides thescattered solar radiance by the object oneself and its own thermal radiance,the systemwill receive some undesirable radiance,which includes scattered radiance by theatmospheric molecules and aerosols and cloud particles,atmospheric thermal radiance,direct solar radiance and so on.The radiance mentioned above constitutes total skybackground radiance.The object-background radiance contrast is a key parameter fordistinguishing an object from the sky background,so the spectral radiance and its scenedistribution constitute the basic database for application to some detection system suchas sky monitoring,aerial target searching and tracking.In the thesis,spectral radianceand scene simulation method for sky background are explored and investigated;thisprovides an important reference to the detection system simulation.The main contents and results are as follows:1.Methods of establishing vertical extinction parameter profile database foratmospheric molecules and aerosols are analyzed.Some scattering phase functions areintroduced for atmospheric molecules and aerosol particles,and their expresses aregiven out under some different conditions.2.Detailed research about the stream approximation of computing downwardspectral radiance for the cloudless sky background is also carried out.A process settingup the Radiative Transfer Equation (RTE) is studied in detail based on the transporttheory.And a universal solution to the RTE is obtained.The discrete ordinate method(DISORT) and the modified Eddington approximate method are employed to treat theproblems of the multiple scattering for the multilayer atmosphere.And some calculationexamples are given out.The results show that the modified Eddington approximatemethod has sufficient precision at least for the examples considered,but shortercomputer time,as compared with the DISORT.3.Approximate methods for computing extinction parameters of the typical waterclouds and ice clouds are studied.Numerical results show that the calculated values based on the new method is consistent well with the values on Mie theory.A way tocalculate cloud affection to the sky background is investigate.4.Based on the energy conservation law and an assumption that the ground is aLambertian reflecting surface,a model is developed to calculate the additional skyradiance due to the ground reflection.According to the ray tracing principle,a newmethod was proposed to compute the effection of the reflection radiance between theearth’s albedo surface and the atmosphere.The results show that sky radiance increasesrapidly with the increase of the ground albedo while a viewing zenith angle is close to90°,i.e.,there is a limb-brightening effect for sky radiance.5.Methods of numerical scene simulation for sky background are analyzed andstudied,and the radiative transfer theory and fractal geometry algorithms aresimultaneity employed to simulate cloud scene.A software was designed to computegeneral spectral radiance and simulate numerical scene for sky background,whichincludes a primary simulation program for cloudy sky also,and an interface programpackage with the object-background synthesis scene is developed.更多还原