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不同尺度粗糙度对月壤微波辐射亮温影响研究

发布时间:2019-01-10 20:02  文章来源:笔耕文化传播
【摘要】:月球表面是粗糙面,既存在地形起伏的大尺度粗糙度,也存在微小尺度的粗糙度。目前国内外关于微尺度粗糙月面对月壤微波辐射亮温的影响的研究都基于几何光学方法,但几何光学只适用于探测波长比散射表面的曲率半径小得多的情况。几何光学模型的一个缺陷是缺乏亮温改变对探测波长的显式依赖关系。在一些地形比较平坦的地区如月海地区,月壤表面可以视为微粗糙表面。本文中,月海地区的月壤被视为多层煤质,表面为微粗糙面,下面各层界面为平面。温度剖面由热传导方程解出。本文采用非相关方法计算媒质的发射率。采用二阶微扰法计算顶层粗糙面对亮温的影响。然后基于所建立的亮温模型,本文仿真分析了不同微粗糙度条件下的Apollo12地区亮温。结果表明,,月面微粗糙度将会增加或降低月表的微波亮温,这取决于微粗糙度、入射角、频率、极化的情况。对CE-1和CE-2微波辐射计而言,其入射角为0°,微粗糙度将会增大月壤亮温。 另一方面,国内外关于大尺度粗糙度对月壤辐射亮温影响的研究比较少。为考虑其影响,本文利用月球轨道激光测高仪(Lunar Orbiter Laser Altimeter,LOLA)的全月高程数据,将CE-2卫星探测时的天线月面足印内的地形视作一个本地倾斜基准面和该基准面上二维粗糙度的叠加,根据倾斜、遮蔽等特点推导有效太阳辐照度的计算公式,然后代入热传导方程,通过改进其数值解法,求解出更加准确的月壤温度剖面,最后将温度剖面代入分层亮温模型,结合月壤分层亮温模型计算了三个典型月陆地区,Apollo15、Aristoteles撞击坑、Hercules撞击坑地区的月壤亮温,最终与CE-2实测亮温进行对比,从而分析地形起伏的大尺度粗糙度对月壤亮温的影响。结果表明,大尺度粗糙面模拟亮温随纬度的变化规律与实测亮温保持一致,这与平面模型相比有很大的改善,从而说明了在计算有地形起伏的亮温时必须考虑大尺度粗糙度的影响。
[Abstract]:The surface of the moon is a rough surface, which has not only the roughness of large scale but also the roughness of small scale. At present, the research on the effect of micro-scale rough moon on the bright temperature of lunar soil microwave radiation is based on geometric optics method, but geometric optics is only suitable for the case where the detection wavelength is much smaller than the curvature radius of the scattering surface. One defect of the geometric optical model is the lack of explicit dependence of the brightness temperature on the detection wavelength. In some flat terrain areas such as the Moon Sea, the surface of lunar soil can be regarded as a slightly rough surface. In this paper, the lunar soil in the Yuehai area is regarded as a multi-layer coal with a surface of slightly rough surface and a plane at the bottom of each layer. The temperature profile is solved by the heat conduction equation. In this paper, the emissivity of the medium is calculated by non-correlation method. The second order perturbation method is used to calculate the effect of the top roughness on the brightness temperature. Then, based on the established bright temperature model, the brightness temperature in Apollo12 region under different micro-roughness conditions is simulated and analyzed. The results show that the surface roughness will increase or decrease the microwave brightness temperature, which depends on the micro-roughness, incidence angle, frequency and polarization. For CE-1 and CE-2 microwave radiometers, the incidence angle is 0 掳, and the micro-roughness will increase the bright temperature of lunar soil. On the other hand, there are few studies on the effect of large-scale roughness on radiative bright temperature of lunar soil at home and abroad. In order to consider its influence, the full moon elevation data of lunar orbit laser altimeter (Lunar Orbiter Laser Altimeter,LOLA) are used in this paper. The topography in the footprint of the lunar surface of the antenna during the CE-2 satellite detection is regarded as a local tilt datum and the superposition of the two-dimensional roughness on the base level. The effective solar irradiance calculation formula is derived according to the characteristics of tilt and obscuration. Then the heat conduction equation is introduced, and a more accurate temperature profile of lunar soil is solved by improving its numerical solution. Finally, the temperature profile is added to the stratified bright temperature model, and the three typical lunar land regions, Apollo15, are calculated in combination with the stratified bright temperature model of lunar soil. The light temperature of lunar soil in Aristoteles crater and Hercules crater area is finally compared with the measured light temperature of CE-2, so as to analyze the influence of the large scale roughness of topographic fluctuation on the light temperature of lunar soil. The results show that the variation of brightness temperature with latitude in large scale rough surface simulation is consistent with the measured brightness temperature, which is greatly improved compared with the plane model. It shows that the influence of large scale roughness must be taken into account in calculating the bright temperature with topographic fluctuation.
【学位授予单位】:华中科技大学
【学位级别】:硕士
【学位授予年份】:2013
【分类号】:P184

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