月表微波辐射与散射计算及次表层结构探测

发布时间：2018-03-08 10:03

本文选题：微波遥感　切入点：辐射与散射　出处：《华中科技大学》2012年博士论文　论文类型：学位论文

【摘要】：上世纪六十年代开始,人类通过各种方式展开了对月球的探测,希望通过研究月球地形、地貌、内部结构和物质组成等信息,了解月球及其它星球的形成和演化历史,并带动一系列相关学科的创新和发展。在探月过程中,微波遥感技术是探测全月球表层土壤内部结构和物质组成的重要手段。由于对月探测的成果无法像对地遥感那样直接取样验证,因此探测结果的正确性依赖于对遥感数据的认识、处理和分析。在这个过程中,月壤模型的建立和分析尤为关键,也成为探月中的重要研究方向。虽然月球距地球十分遥远,但微波辐射理论和电磁散射理论为月壤辐射与散射特性的研究提供了强有力的理论基础,而计算机性能的提高以及高性能、集群式工作站的出现更是为定量计算月表辐射亮温和散射系数等特性提供了硬件基础。通过这种数值计算的方式,可以有效地研究不同月壤模型的辐射与散射特性,并在此基础上提出月表探测方案及月壤相关参数的反演方法。将理论分析结果与实测数据对比,有利于正确阐释遥感数据中的月壤特征,认识月壤内部的真实结构。因此,本文围绕月表辐射和散射的数值计算展开了相关研究工作,主要包括：首先对微波辐射测量和电磁散射计算的基础理论进行了介绍,在总结月壤相关研究(如月表粗糙度、月壤温度剖面、月壤模型等)的基础上,结合月壤次表面结构和水冰探测的需要,提出了包含月表粗糙性的多层物理模型,为研究粗糙月表的辐射与散射特性打下基础。同时,为减少数值计算的复杂度,采用高斯随机粗糙面,研究了一维粗糙面和二维粗糙面间的差异。研究结果表明,当二维粗糙面在两个维度上具有相同的粗糙度时,可以采用一维粗糙面进行模拟仿真,有利于降低数值计算的复杂度。其次,基于多层月壤物理模型,研究了月表辐射亮温和散射特性的计算方法。对于辐射亮温,提出了微波辐射传输理论与矩量法相结合的混合方法,用于研究粗糙月表的辐射亮温,并对方法的有效性进行了验证。研究结果表明：月表粗糙度会对辐射亮温产生影响,且与辐射计极化状态和观测角有密切关系；通过调整辐射计观测角,在垂直极化状态下能够将粗糙度的影响降至较低水平,从而利于月壤参数的反演。对于月壤散射特性,研究了次表面回波与表面回波的相干性,并在此基础上提出了采用步进频率雷达进行次表面结构探测的方案。结合矩量法计算结果,对探测方案的性能进行了讨论,结果表明：步进频率信号能提供更丰富的散射信息,使该方案在月表粗糙度较大情况下,仍然能够对次表面结构进行探测,但需要分层面上下媒质的介电常数差异足够大。在数值计算方法研究的基础上,对月壤中可能存在的水冰带来的影响进行了分析。当月壤中含有水冰时,会引起发射率增加、辐射亮温升高等现象,但单一的探测手段不足以对水冰的存在及含量进行判断,需借助多遥感设备进行复合探测,并对月壤参数进行联合反演。再次,为了配合月表散射特性计算,针对月壤模型的大尺度、多层粗糙面等结构特点,提出了广义带状矩阵迭代(GBMIA)算法,并用矩量法对新算法的精确度进行了检验。结果表明：GBMIA既降低了存储量,又节省了计算时间,并且不会对计算结果带来太大误差,适合研究月表散射特性。最后,研究了系统空间分辨率的增强算法。采用信号处理方式等效于减小天线波束覆盖范围,从而降低月壤模型的计算规模。仿真和实验结果表明,本文通过改进高频提升法,使系统空间分辨率进一步提高,而且反演结果更准确。
[Abstract]:In the beginning of 60s, humanity has launched the lunar exploration through a variety of ways, hope through the study of lunar topography, landform, internal structure and material composition information, understand the formation of the moon and other planets and the evolution history, and promote the innovation and development of a series of related disciplines. In lunar exploration process, microwave remote sensing technology is an important means to detect the whole lunar surface soil internal structure and material composition. Because the moon exploration results not as verification of remote sensing as a direct sampling, so the correctness of the results depends on the knowledge of remote sensing data, processing and analysis. In this process, the lunar regolith model construction and analysis has become particularly critical, an important research direction of lunar exploration.
Although the moon is very far from the earth, but provides a strong theoretical basis on the theory of microwave radiation and electromagnetic scattering theory of lunar radiation and scattering properties, and the improvement of computer performance and high performance, appearance of the cluster workstation is to provide a hardware based shot brightness temperature and scattering coefficient characteristics for the quantitative calculation of the lunar radiation. Through the numerical calculation, the radiation and scattering characteristics can effectively study different lunar soil model, based on the inversion method of lunar regolith scheme and related parameters. The comparison between theoretical analysis results and the measured data are lunar features for the correct interpretation of remote sensing data, know the real structure of July the soil inside. Therefore, the calculation carried out the relevant research work of this paper focuses on numerical lunar radiation and scattering, including:
The basic theory of microwave radiation first measurement and calculation of the electromagnetic scattering are introduced in the related research summary of lunar regolith (surface roughness, such as lunar regolith model of temperature profile, etc.) on the basis of combining with the need of lunar subsurface structure and detection of water ice, which contains the physical model of surface roughness of multilayer and lay the foundation for the radiation and scattering characteristics of rough surface. At the same time, to reduce the complexity of numerical calculations, the Gauss studies the one-dimensional random rough surface, rough surface and rough surface. The difference between the results of the study show that, when the two dimensional rough surface in two dimensions with the same roughness. The one-dimensional rough surface is simulated. To reduce the complexity of calculation.
Secondly, based on the physical model of multilayer regolith, calculation method of the surface radiation brightness temperature and scattering characteristics. The brightness temperature, proposes a hybrid method combining microwave radiative transfer theory and the method of moments, for the study of rough surface radiation brightness temperature, and the effectiveness of the method was verified. The results of the study show that the surface roughness will affect the brightness temperature, and radiometer polarization state and observation angle are closely related; perspective angle by adjusting the radiation, the effect of roughness can be reduced to a lower level in the vertical polarization, thus contributing to the inversion of lunar regolith parameters. The scattering characteristics of lunar regolith, research the coherence time surface echo and surface echo, and on the basis of the step frequency radar surface structure detection scheme. The calculation results with the method of moments, the detection scheme of can The discussion shows that the stepped frequency signals can provide more information of scattering, the scheme on the lunar surface roughness is larger, can still detect the surface structure, but need to face layered medium dielectric constant difference is large enough. Based on the numerical method research, influence water ice may exist in lunar regolith have been analyzed. The soil containing water ice, will cause the emission rate increased, the brightness temperature rising phenomenon, but a single means is not enough to exist and content on the ice to judge, to compound detection by means of multi remote sensing equipment, and the lunar regolith parameters were combined inversion.
Again, in order to cope with the surface scattering characteristics for large scale calculation, regolith model, multilayer rough surface structure characteristic, proposed a generalized banded matrix iterative (GBMIA) algorithm, and test the accuracy of the new algorithm using the moment method. The results show that GBMIA not only reduces the amount of storage, but also saves computing time not too much, and the error of calculation results, suitable for surface scattering characteristics research.
Finally, the system spatial resolution enhancement algorithm. By using the signal processing method is equivalent to reduce the antenna beam coverage, so as to reduce the calculation scale of lunar soil model. The simulation and experimental results show that the improved high-frequency lifting method, the spatial resolution of the system further improved, and the accuracy of the inversion results.

【学位授予单位】：华中科技大学
【学位级别】：博士
【学位授予年份】：2012
【分类号】：P184

【参考文献】