月表微波辐射对月壤厚度及其物理温度廓线的反演

以中国"嫦娥"1号(CE-1)卫星多通道微波辐射计对月球辐射亮度温度测量数据,选取月球两极、赤道与沿经度150°W作为目标区域,结合月表面地形的数字高程模型(DEM),讨论环形山月球表面(特别是光照度低的两极区域)微波辐射亮度温度的分布。由昼夜温度变化产生的月壤物理温度分布廓线的三层辐射传输理论模型为基础,结合阿波罗登月点月壤厚度测量数据,用CE-1多通道微波辐射观测数据反演与讨论了目标区域的月壤层物理温度廓线及其月壤层厚度。     

基于深度学习的探月雷达对月面浅表层不规则形状介质预测

在月壤中掩埋的岩块几何形状和电性特征分布具有显著的不确定性，探月雷达(LPR)获得的回波信号的特征复杂，无法有效地对月壤内部结构进行精确的几何成像。该文提出一种基于主成分分析降维的深度学习数据处理方法，用于复杂月表以下岩石分布结构的快速数字化成像，可以直接建立回波信号特征与月岩几何拓扑的关联关系。首先基于Apollo探月任务返回的月岩样品照片，利用边缘检测等图像处理方法提取月岩介质的几何轮廓，构建含有月岩块体的地层模型；针对信息冗余的时域回波信号，采用主成分分析法对高维空间的回波数据进行降维处理，然后利用基于均方根传递(RMSprop)的反向传播算法构建针对月岩介质上表面轮廓和位置的拟合预测模型。仿真结果表明，对于掩埋的具有复杂几何特征和高介电常数的单月岩块地层结构，深度学习R-square确定系数可达到0.93，月岩上表面轮廓和位置预测结果与真实模型重合度较高；同时也对复杂多月岩随机分布模型进行了探索性神经网络几何重建建模和验证。此工作为后续地质科学领域开展基于数据驱动模型的地层成像相关研究提供了初步的参考。     

光学观测与微波辐射模拟对月壤厚度的反演

由月球正面的光学反照率,根据颗粒表面分光反照率的几何光学模型,计算月球正面FeO TiO2含量的分布.根据月球正面数字高程(DEM,digital elevation mapping)与FeO TiO2含量之间的统计关系,由月球背面DEM构造月球背面的FeO TiO2含量分布.由整个月球表面的FeO TiO2含量分布,计算月球表面介电常数的分布.依据月球表面温度分布以及由DEM对应构造的月球表面月壤厚度,由起伏逸散定理,模拟计算了3,7.8,19.35,37GHz四个通道平行分层月壤微波辐射亮度温度的月球表面分布.以此模拟分布为理论观测值,提出三通道-两通道相结合的月壤厚度反演方法.当FeO TiO2含量较低,各通道辐射亮度温度有差异时,采用三通道方法反演月壤厚度;当FeO TiO2含量过高,使得高频7.8,19.35,37GHz的辐射亮度温度由于饱和而趋于相同时,采用两通道方法反演月壤厚度.若金属含量过高,而可能使四个通道辐射亮度温度都不易区分时,由FeO TiO2含量可以确定出月壤厚度的下限值.为现有的多通道微波探月提供一个可行的月壤厚度反演方法,也有助于月球表面辐射亮度温度的定标与验证.     

三维非均匀散射层与其中异常目标的辐射传输

讨论了三维非均匀散射层与其中有异常目标的矢量辐射传输高阶散射与辐射的求解与数值模拟.将三维非均匀散射介质在垂直方位z轴方向划分成许多薄层,再在水平(x,y)方位上划分成方格,用分割形成的各薄盒的零阶热辐射和一阶Mueller矩阵解,推导多阶辐射传输的迭代方法,获得整个散射介质三维VRT方程的高阶散射与辐射解.模拟了微波频段在各空间分辨率的辐射计观测下非均匀植被层和地面上有异常目标的极化辐射亮度温度的观测图像.     

星载微波ERS-1和多通道SSM/I观测冰雪的相关性和多层随机介质的数值模拟

该文研究了星载微波ERS－1散射计和多通道SSM／I辐射计在格陵兰岛、西伯利亚和阿尔卑斯山等地观测到的后向散射和热辐射数据，论证了同一地区同一时间段内ERS主动散射计和SSM／I被动辐射计观测数据的相关性。用冰雪覆盖区域的主被动遥感数据的比较，阐述了主被动联合多通道分析方法有利于监视和分析复杂地表在时间和空间尺度上的变化。该文用多层强起伏随机介质的后向散射模拟ERS数据，用多层密集散射粒子介质的辐射传输模拟SSM／I数据。讨论了后向散射与热辐射数值模拟结果的相关性，以及与星载微波遥感器实际观测结果的比较。     

随机降雨层的电磁波矢量辐射传输分析

讨论了随机降雨层中的电磁波矢量辐射传输问题。根据一种具有两种降雨强度大小的随机降雨层模型,建立相应的矢量辐射传输方程,给出了一种求解方法。用Monte Carlo方法验证了该方法的正确性,讨论了随机降雨层和确定降雨层之间的区别和联系以及随机降雨层参数变化对结果的影响,最后讨论了随机介质和两种平均介质之间的关系。     

辐射对准周期多层平板介质栅传输特性的影响

本文多模网络理论与模匹配相结合的方法对准周期多层平板介质栅的传输特性进行了系统的分析，深入讨论了辐射现象对准周期传输特性的影响，为各种介质栅结构的精确设计了依据。     

固定指向型微波辐射计辐射传输模型分析

固定指向型微波辐射计通常采用多支路法进行定标，传输路径上的各微波组件存在一定的插入损耗，且组件间还存在阻抗失配，因此需要首先建立信号源经馈源口面至接收机输入端口处的辐射传输模型，然后结合两点定标法确定固定指向型微波辐射计的定标模型。首先对同类型微波辐射计的辐射传输模型进行叙述，然后采用正交试验设计法定量地分析了辐射传输模型中各组件对接收机等效输入噪声温度误差影响的大小以及主次关系，为同类型微波辐射计的辐射传输模型建立和定标模型初始参数的选取提供参考。     

嫦娥五号探月雷达的数据处理方法研究

探月雷达对于认识月球和开发月球资源具有重要意义,我国发射的嫦娥五号探测器已于2020年12月1日在月球表面着陆,圆满完成了嫦娥三期工程“采样返回”任务。根据嫦娥五号的任务安排,月壤结构仪在月表采集的雷达数据传回地表后,需要准时对月壤钻头下方2 m深度范围内的月壤结构和可能存在的月岩进行高分辨率成像,为后续月壤钻取任务提供关键的信息支持。本文研究了复杂电磁环境下嫦娥五号探月数据的杂波去除方法,通过速度谱分析法反演月壤分层结构的介电常数,并开发了基于矢量格林函数的频率域快速逆时偏移成像算法。仿真和地面验证试验结果表明:利用速度谱分析方法获取的月壤分层结构介电常数和厚度误差在12%以内,可为逆时偏移成像提供精准的初始模型;研发的频率域逆时偏移算法,可在快速获取月壤中月岩的高分辨率成像结果,为后续月壤采样任务提供准确的信息支持。研究成果为嫦娥五号月壤钻取任务的顺利实施提供了支撑,并将有助于嫦娥五号探月雷达数据的精细化处理,从而深化月壤起源和演化机理的认识。     

共面波导电极聚合物电光调制器多层结构研究

提出了两种基于共面波导(CPW)电极的多层聚合物电光调制器模型结构,分别为补偿层型结构和屏蔽层型结构。采用了保角变换的计算方法给出了基于CPW电极结构的多层电光调制器的特性参数的计算结果。与传统调制器结构性比较,补偿层型结构能够有效的减小光波与微波传输有效折射率的差,屏蔽层型结构不仅能够减小光波与微波传输有效折射率的差,而且能够通过优化结构参数,有效地消除了微波与光波之间的折射率差,可实现调制信号速率和调制电极阻抗的同时匹配。     

Exploring the potential for multipatch soil-moisture retrievalsusing multiparameter optimization techniques

This paper explores the potential to retrieve surface soil moisture and optical depth simultaneously for several different patches of land cover in a single pixel from dual polarization, multiangle microwave brightness temperature observations such as will be provided by, for instance, the Soil Moisture and Ocean Salinity (SMOS) mission. MICRO-SWEAT, a coupled land-surface and microwave emission model, was used in a. year-long simulation to define the patch-specific soil moisture, optical depth, and synthetic, pixel-average microwave brightness temperatures similar to those that will be provided by SMOS. The microwave emission component of MICRO-SWEAT also forms the basis of an exploratory retrieval algorithm in which the difference between (synthetic) observations of microwave brightness temperatures and modeled, pixel-average microwave brightness temperatures for different input values of soil moisture and optical depth is minimized using the shuffled complex evolution (SCE) optimization procedure. Results are presented for two synthetic pixels, one with eight patches, where only the soil moisture is retrieved, and one with five patches, where both the soil moisture and the optical depth are retrieved     

A sensitivity analysis of soil moisture retrieval from the tau-omega microwave emission model

The potential of the /spl tau/--/spl omega/ model for retrieving the volumetric moisture content of bare and vegetated soil from dual-polarization passive microwave data acquired at single and multiple angles is tested. Measurement error and several additional sources of uncertainty will affect the theoretical retrieval accuracy. These include uncertainty in the soil temperature, the vegetation structure, and consequently its microwave single-scattering albedo, and uncertainty in soil microwave emissivity based on its roughness. To test the effects of these uncertainties for simple homogeneous scenes, we attempt to retrieve soil moisture from a number of simulated microwave brightness temperature datasets generated using the /spl tau/--/spl omega/ model. The uncertainties for each influence are estimated and applied to curves generated for typical scenarios, and an inverse model used to retrieve the soil moisture content, vegetation optical depth, and soil temperature. The effect of each influence on the theoretical soil moisture retrieval limit is explored, the likelihood of each sensor configuration meeting user requirements is assessed, and the most effective means of improving moisture retrieval indicated.     

Multifrequency Microwave Radiometer Measurements of Soil Moisture

Ground-based microwave radiometer experiments were performed to investigate the effects of moisture, temperature, and roughness on microwave emission from bare soils. Measurements were made at frequencies of 0.6-0.9, 1.4, and 10.7 GHz using van-mounted radiometers to observe prepared soil sites in Kern County, CA. The sites were instrumented for monitoring soil characteristics and surface meteorological conditions. Brightness temperature variations of approximately 15 K at 1.4 GHz and 25 K at 10.7 GHz were observed as a result of diurnal changes in the soil temperature. Increasing the soil moisture content from 2 to 15 percent by volume resulted in brightness temperature decreases of approximately 70 K at 0.775 and 1.4 GHz, and 40 K at 10.7 GHz, depending, to a lesser extent, on polarization and viewing angle. The results show the significance of soil temperature in deriving soil moisture from microwave radiometer measurements. Comparisons of the microwave measurements with theoretical predictions using a smooth surface model show reasonable agreement and support previous results of this nature obtained with other soil types. Approximately equal sensitivity to soil moisture was observed at 0.775 and 1.4 GHz, although the sampling depth is greater at the lower frequency.     

Impact of horizontal and vertical heterogeneities on retrievals using multiangle microwave brightness temperature data

This paper investigates the impact of heterogeneity at the land surface on geophysical parameters retrieved from multiangle microwave brightness temperature data, such as would be obtained from the Soil Moisture and Ocean Salinity (SMOS) mission. Synthetic brightness temperature data were created using the Common Land (land surface) Model, coupled with a microwave emission model and set within the framework of the North American Land Data Assimilation System (NLDAS). Soil moisture, vegetation optical depth, and effective physical temperature were retrieved using a multiobjective calibration routine similar to the proposed SMOS retrieval algorithm for a typical on-axis range of look angles. The impact of heterogeneity both in the near-surface profiles of soil moisture and temperature and in the land cover on the accuracy of the retrievals was examined. There are significant errors in the retrieved parameters over regions with steep gradients in the near-surface soil moisture profile. These errors are approximately proportional to the difference in the soil water content between the top (at 0.7 cm) and second layer (at 2.7 cm) of the land surface model. The errors resulting from heterogeneity in the land cover are smaller and increase nonlinearly with increasing land-surface heterogeneity (represented by the standard deviation of the optical depth within the pixel). The most likely use of retrieved soil moisture is through assimilation into an LDAS for improved initiation of weather and climate models. Given that information on the soil moisture profile is already available within the LDAS, the error in the retrieved soil moisture as a result of the near-surface profile can be corrected for. The potential errors as a result of land-surface heterogeneity can also be assessed for use in the assimilation process.     

A methodology for surface soil moisture and vegetation opticaldepth retrieval using the microwave polarization difference index

A methodology for retrieving surface soil moisture and vegetation optical depth from satellite microwave radiometer data is presented. The procedure is tested with historical 6.6 GHz H and V polarized brightness temperature observations from the scanning multichannel microwave radiometer (SMMR) over several test sites in Illinois. Results using only nighttime data are presented at this time due to the greater stability of nighttime surface temperature estimation. The methodology uses a radiative transfer model to solve for surface soil moisture and vegetation optical depth simultaneously using a nonlinear iterative optimization procedure. It assumes known constant values for the scattering albedo and roughness, and that vegetation optical depth for H-polarization is the same as for V-polarization. Surface temperature is derived by a procedure using high frequency V-polarized brightness temperatures. The methodology does not require any field observations of soil moisture or canopy biophysical properties for calibration purposes and may be applied to other wavelengths. Results compare well with field observations of soil moisture and satellite-derived vegetation index data from optical sensors     

Analysis of Thermal Radiation from an Inhomogeneous Cylindrical Human Body Model

The thermal radiation from a cylindrical human body model at microwave frequencies is treated analytically. The human body model is taken to be a homogeneous cylinder at temperature T having a localized internal thermal inhomogeneity at temperature T + Delta T. The mean energy density for the near field outside the cylinder is determined by employing the dyadic Green's function of the homogeneous cylinder and the fluctuation-dissipation theorem. Analytical results are derived for the contributions of the homogeneous cylinder and the inhomogeneity region. Numerical results are presented for several geometries at low microwave frequencies where a reasonable transparency of tissues is expected. The possibility of using microwave radiometry techniques to measure temperature distributions in depth is discussed in relation to hyperthermia and the development of noninvasive diagnostic techniques. It is shown that the emission from surrounding tissues limits the detectability of thermal inhomogeneities inside the body and that by using low microwave frequencies (~1 GHz), temperature measurement at depths up to 2 cm can be performed.     

Using a modeling approach to predict soil hydraulic properties frompassive microwave measurements

A soil water and energy budget model coupled with a microwave emission model (MICRO-SWEAT) was used to predict the diurnal courses of soil surface water content and microwave brightness temperatures during a number of drying cycles on soils of contrasting texture that were either cropped or bare. The parameters describing the soil water retention and conductivity characteristics [saturated hydraulic conductivity, air entry potential, bulk density, and the exponent (b) describing the slope of the water release curve] had a strong influence on the modeled bare-soil microwave brightness temperatures. These parameters were varied until the error between the remotely sensed and modeled brightness temperatures was minimized, leading to their predicted values. These predictions agreed with the measured values to within the experimental error. The modeled brightness temperature for a soybean-covered soil was sensitive to some of the vegetation parameters (particularly to the optical depth), in addition to the soil hydraulic properties. Preliminary findings suggest that, given an independent estimate of the vegetation parameters, it may still be possible to estimate the soil hydraulic properties under a moderate vegetation canopy