基于DEM的月表亮温模拟的研究

发布时间：2018-06-21 06:14

本文选题：嫦娥一号 + DEM　；参考：《华中科技大学》2012年硕士论文

【摘要】：月壤厚度是探索月球的四大重要目标之一，反演月壤厚度需要建立准确的微波辐射亮温模型。本文详细讨论了月壤辐射传输模型的发展过程及影响亮温的重要因素，如地形、邻坡散射和微尺度的粗糙度，并在现有的亮温模型基础之上，利用嫦娥一号CCD影像与辐射计的同轨特性，添加了重要的地形因素，从理论上可以模拟月表任意时刻、任意位置的亮温，并且能够直接和微波辐射计实测数据相比较，这是新模型与之前的亮温模型之间最突出的区别。为了利用与微波辐射计同轨扫描的CCD影像生成DEM，本文首先介绍了基于三线阵CCD影像的三维建模的流程，并以Hercules撞击坑为例，发现计算的DEM主要存在粗差簇和粗差线两种粗差，讨论了这两种粗差的特点和形成原因，并提出局部仿射变换抑制粗差簇，以角锥体法代替经典答解方法来抑制粗差线。最后以有效太阳辐照度图像较好地反映出DEM中的撞击坑的轮廓信息，通过比较证明修正后的DEM精度有了较大的提高，并由此得到一些关于粗差线的初步结论。在得到DEM之后，通过地形修正和遮蔽可计算出有效太阳辐照度，并通过实例证明了地形修正的确能够造成辐照度的局部增强和局部衰减，并且遮蔽区域和CCD影像较好地符合。然后针对当前的热传导方程不能适用于任意月壤厚度的问题，分析了热传导方程的迭代稳定条件，并提出了一种新的自适应分层方法。为了与实测数据相比较，在计算出DEM每个网格点的温度后，采用基于天线方向图的方法对亮温进行归一化，得到了和微波辐射计同时刻、同区域的模拟亮温。针对Hercules坑的实测微波数据在白天和夜晚都出现较大波动的现象，模拟了Hercules坑在这两个时刻的亮温，还验证了平坦区域的亮温变化情况。结果表明：模拟亮温的变化趋势总体上和实测亮温相符合，，从而直接证明了地形能够对亮温造成较大影响。此外，本文对亮温发射角和天线方向图进行了初步分析，并得到了一些结论。
[Abstract]:The thickness of lunar soil is one of the four important objectives of lunar exploration. It is necessary to establish an accurate bright temperature model of microwave radiation for retrieving the thickness of lunar soil. In this paper, the development process of lunar soil radiative transport model and the important factors affecting the brightness temperature, such as topography, adjacent slope scattering and micro-scale roughness, are discussed in detail. By using the same orbit characteristic of Chang'e 1 CCD image and radiometer, an important terrain factor is added, which can theoretically simulate the bright temperature at any position and at any time on the moon surface, and can be compared directly with the measured data of microwave radiometer. This is the most striking difference between the new model and the previous bright temperature model. In order to make use of CCD images scanned in the same orbit with microwave radiometer to generate demm, this paper first introduces the process of 3D modeling based on three-line CCD images. Taking the Hercules impact crater as an example, it is found that there are two kinds of gross errors in Dem. The characteristics and causes of these two gross errors are discussed. The local affine transformation is proposed to suppress the gross error clusters and the corner cone method is used instead of the classical solution method to suppress the gross error lines. Finally, the contour information of the impact crater in Dem is well reflected by the effective solar irradiance image, the accuracy of the modified Dem is proved to be greatly improved by comparison, and some preliminary conclusions about the gross error line are obtained. After getting Dem, the effective solar irradiance can be calculated by terrain correction and masking, and it is proved by an example that topographic correction can cause local enhancement and local attenuation of irradiance, and the shaded area is in good agreement with CCD image. Then the iterative stability condition of the heat conduction equation is analyzed and a new adaptive stratification method is proposed to solve the problem that the current heat conduction equation is not suitable for any lunar soil thickness. In order to compare with the measured data, after calculating the temperature of each grid point of Dem, the method based on antenna pattern is used to normalize the brightness temperature, and the simulated bright temperature at the same time as the microwave radiometer is obtained. Aiming at the phenomenon that the observed microwave data of Hercules crater fluctuate greatly during day and night, the light temperature of Hercules crater at these two times is simulated, and the variation of light temperature in flat region is verified. The results show that the variation trend of simulated brightness temperature is consistent with the measured light temperature in general, which directly proves that the topography can have a great influence on the light temperature. In addition, the light temperature emission angle and antenna pattern are preliminarily analyzed and some conclusions are obtained.
【学位授予单位】：华中科技大学
【学位级别】：硕士
【学位授予年份】：2012
【分类号】：P184.53

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