【作者】 张寅；

【导师】 丛明煜； 王治乐；

【作者基本信息】 哈尔滨工业大学 ， 光学工程， 2016， 博士

【摘要】 大气是天基光学遥感链路上的重要环节,对大气辐射特性的认知程度直接影响到光电探测系统的设计与评估水平,进而影响到探测数据的信息质量与有效性,是探测/遥感任务成功执行的前提;另一方面,从大气的光谱辐射特性中可以反演出地球系统在广域时空范围内的物性状态变化信息,是研究地球科学的重要手段。目前,实测积累与数字仿真是提高对大气背景认识水平的两种最有效手段。本文以我国首颗红外大气背景遥感卫星的业务需求为应用背景,立足于测量数据的定量化处理与后期应用,对红外大气背景图像数据的处理技术与仿真方法开展了深入系统的研究,在数据处理方面的研究成果已经应用于该卫星的地面数据处理系统,而在云层图像仿真方面建立的模型与形成的方法可以为我国天基红外成像探测系统的指标论证、性能评估以及大气的物性参数反演等工作提供理论与数据支持。论文的研究工作从以下五个方面开展:在总体技术研究方面,阐述了我国大气背景遥感卫星红外相机的工作原理、测量模式与系统组成;在此基础上,根据相机的测量任务与实际工况,将辐射定标和几何信息解算作为测量数据处理中的核心内容,并设计了研究方案;结合实测图像数据与实际应用需求,分别提出了基于大气背景辐射亮度图像数据统计特性和基于场景建模与辐射传输的云层图像仿真方案。在测量数据的辐射定标处理技术方面,从红外相机测量对象的辐射特性出发,给出了红外相机的辐射定标原理与黑体选择依据,并对地面定标试验方法与结果进行了描述;根据在轨定标试验制定了数据处理流程,结合实际下传数据,总结出三类无效数据的特征与相应剔除方法;分析了相机在轨响应衰减现象,建立了具有一定物理意义的相机响应衰减模型;在此基础上,提出了相机内部污染容限的判断准则与定标系数的估计方法。在测量数据的几何信息处理技术方面,根据相机的实际观测模式与测量对象,将拍摄图像分类为地球背景、临边背景与空间背景;分析了不同类型背景所关注的几何信息差异,设计了不同的几何解算内容,并给出了相应的计算方法;利用卫星实际下传的姿轨等数据,将几何解算结果与STK进行了比对,验证了计算模型的正确性,同时给出了实测图像几何解算结果的应用举例。在实测大气背景辐射亮度数据统计特性分析与仿真应用方面,分析了红外短波实测图像的辐射亮度分布与功率谱密度统计特性,在此基础上,论证了利用分形理论进行云层仿真的可行性与合理性;引入二维多尺度叠加分形算法构造云层图像的纹理结构;通过数值实验,研究了分形算法控制参数与生成图像统计特征之间的关系,对算法的参数估计问题进行了探讨;基于红外相机实测云层图像,验证了仿真方法的有效性和可用性。在基于三维场景建模与辐射传输的云层图像仿真方面,使用三维多尺度叠加分形算法构造云层的空间含水量分布;给出了球形粒子与随机取向的非球形粒子的单次散射特性计算方法;重点对水平取向平板粒子的镜向散射相函数进行了建模研究,并利用T矩阵与Monte-Carlo法进行了模型验证;根据云层和大气的光学特性,建立了适用于吸收波段的三维辐射传输模型与相关k分布参数优化方法,并使用球谐离散坐标法对计算精度进行了验证;最后,利用上述仿真体系对不同结构、不同高度、不同散射特性的三维云层进行了仿真应用。更多还原

【Abstract】 Atmosphere is an important part in space-based optical remote sensing chain. The cognition degree of atmospheric radiative characteristics directly affects the design and evaluation of photoelectric detection systems, and then the information quality and effectiveness of obtained data, thereby being a prerequisite for successfully executing remote sensing or detection missions. On the other hand, physical state changing information of the earth system over a wide range of spatial and temporal scales can be retrieved from the spectral radiative characteristics of the atmosphere, which is an important means to study earth sciences. At present, measurement and digital simulation are the two most proven ways to improve the knowledge level of the atmospheric background.This dissertation regards the mission requirement of China’s first atmospheric remote sensing satellite as the application background. The processing techniques and simulation methods of the infrared atmospheric image data are investigated deeply and systematically for the purpose of quantitative treatment and future application of the measured data. The research findings in data processing have already been applied to the satellite ground data processing system, while the formed models and methods in cloud image simulation are of great value to the specification determination and performance evaluation of space-based infrared imaging systems as well as to the inversion of atmospheric physical parameters both in theoretical and technical assistance. The main contents of this dissertation are organized as following:General design of the research scheme. The operation principles, modes and composition of the infrared camera are explained. Considering the practical measurement tasks and operating conditions of the camera, the radiometric calibration and geometric information acquirement are regarded as the core contents in measured data processing, and their corresponding research schemes are designed. According to the measured data and the practical application requirements, t wo simulation schemes are proposed, one relies on the statistic characteristics of the measured atmospheric radiance image data, and the other is on the basis of scene modeling and radiative transfer calculation.Study on the processing technologies of radiometric calibration. The calibration principle and the selection basis of calibration source are given from the radiative characteristics of measuring objects. The process and results of the pre-launch calibration test are presented. The data processing flow is formulated according to the process of the on-orbit radiometric calibration test. Three types of invalid calibration data are summarized and their filtering strategies are provided as well. A degradation model is proposed to characterize the camera response over time, and its applications are discussed in determining contamination tolerance and estimating calibration coefficients.Study on the processing technologies of acquiring the geometric information attached to the measured data. The imaging data are classified into earth background, limb background and space background according to the observing modes and measuring objects. The required geometric information for different background types is determined after analyzing, and their calculation models are provided and validated by comparing with STK results using the actual downlinked camera status data. Application examples of the solved geometric information are given at the same time.Study on the statistical characteristic analysis and simulation application of the measured atmospheric radiance data. The radiance distribution and power spectral density of the shortwave infrared(SWIR) images are analyzed. The feasibility and rationality of using fractal theory to generate cloud image are demonstrated. The two-dimensional(2D) rescale-and-add(RSA) fractal algorithm is introduced to construct the cloud texture structure. By numerical experiment, the relationship between the RSA algorithm parameters and the statistical characteristics of the simulated images is studied, and the method of parameter estimation is discussed. The measured images and the simulated images are compared to validate the effectiveness of the proposed simulation method.Study on the cloud image simulation method based on three-dimensional(3D) scene modeling and radiative transfer calculation. The RSA algorithm is extended to 3D to generate the spatial structure of cloud liquid/ice water content. The calculation methods of single scattering properties for spherical particles and randomly oriented non- spherical particles are given. The specular scattering phase function for horizontally oriented particles is modeled theoretically as a research focus, and is validated by the T-matrix and the Monte-Carlo method. A 3D radiative transfer model and a new optimization technique for the correlated k distribution parameters are proposed specially for absorption bands, and their accuracy is validated using the spherical harmonics discrete ordinate method(SHDOM). Finally the above simulation system is applied to 3D clouds with different structures, hei ghts and scattering properties.更多还原