基于大气辐射传输模型的地物偏振反射率反演方法

提出一种基于大气矢量辐射传输模型的地物偏振反射率反演方法.利用辐射传输模型,建立地表反射率、观测条件与传感器入瞳处辐亮度偏振态的查找表,再进行查找表反查及数值计算,完成偏振反射率反演.验证实验表明,典型地面目标物的偏振反射率反演精度可达到90%.     

基于MODIS红外通道的辐射传输计算

通过建立地气系统的红外辐射传输方程,基于MODIS红外通道进行辐射传输计算.利用快速精确的透过率模型PFAAST计算大气透过率,在红外辐射传输计算中考虑了地面反射大气辐射亮度的影响,指出地面反射大气辐射亮度在整个方程所占比重随着地表发射率变小而增加,其中MODIS第33通道对发射率的改变最为敏感,美国标准大气下,当发射率ε=0.65时,比重达到7.12%,因此,忽略地面反射大气辐射亮度,直接影响红外辐射传输计算的准确性.模拟了MODIS各红外通道辐射亮度,并与MODTRAN4.0模拟结果比较,相对误差不超过0.12%,模拟了大气倾斜路径对卫星红外通道观测亮温的影响.     

Indoor C-band polarimetric interferometry observations of a mature wheat canopy

We present results from experiments carried out in the ground-based synthetic aperture radar (GB-SAR) facility at the University of Sheffield to ascertain the role of polarimetric interferometry in crop height retrieval. To this end, a mature wheat canopy, grown in outdoor conditions, was reassembled inside the GB-SAR chamber and imaged at C-band using a two-dimensional scan. This allowed fully polarimetric tomography and interferometry. Interferometry using the VV, HH, and VH polarization states shows that the HH and VH interferograms retrieve a height close to the top of the soil layer for all angles of incidence considered, whereas the height retrieved from the VV interferogram increases with angle of incidence. The use of a Pauli basis gives poor results, due to the different location of the scattering phase centers in the VV and HH channels. The use of arbitrary polarization states shows that the top of the soil can be very accurately estimated using left-circular polarization, whereas, for angles of incidence close to 45/spl deg/, a polarization state similar to VV can be used to retrieve the top of the canopy; hence crop height can be recovered as the difference of these two interferometric heights. Polarimetric coherence optimization techniques are also studied. Unconstrained coherence optimization gives very unstable results, due to the small number of available samples. Constrained optimization results in stable retrieved heights, and the retrieved polarization states agree well with the polarization synthesis results.     

基于辐射传输模型的TDI CCD遥感相机信噪比分析

信噪比是定量评价遥感相机成像质量和辐射性能的一项关键指标,信噪比的估算和测试对于遥感相机的研制至关重要.针对TDI CCD相机从辐射传输和能量转换的角度推导了信噪比计算公式,基于大气辐射传输模型MODTRAN 4.0从理论上估算了某遥感相机在各种观测条件下的信噪比,结果表明:在典型观测条件下相机的信噪比不低于20 dB.作为试验验证,利用积分球光源对相机进行了各种照明条件下的信噪比测试,测试结果证实了理论模型的正确性.     

Rapid radiative transfer model for AMSU/HSB channels

The atmospheric transmittance model for the Advanced Microwave Sounding Unit-A (AMSU-A) and the Humidity Sounder for Brazil (HSB) channels on the Aqua spacecraft uses a polynomial approximation to the temperature dependence of oxygen-band opacity within atmospheric layers. It uses lookup tables to calculate local water-vapor line intensity and pressure-broadening parameters as well as contributions to absorption from the water-vapor continuum, distant lines, and cloud liquid water. The algorithm includes water-line self-broadening and the magnetic-field effect on AMSU-A channel 14. The microwave surface emission model is based on a preliminary classification of the surface type, with subsequent adjustments to the emissivity spectrum that are obtained from the retrieval algorithm. A simple approximate correction for surface nonspecularity is included. The algorithm has been tested by comparisons to a line-by-line calculation and to measurements made by the NOAA-15 AMSU-A.     

Estimation of radiative heat transfer using a geometric human model

In order to provide a detailed estimate of radiative heat transfer between a human body and its surrounding environment, we have developed a geometric model of a human form and an algorithm. The model closely resembles the actual shape of a human body and is composed of small quadrilateral surfaces. Dealing with an object or a space with an arbitrary shape, the developed algorithm can judge efficiently whether there is an obstruction between a pair of surfaces. As a result, the angle factors between a pair of surfaces that only occur during radiative heat transfer can be defined. The distribution of the radiative heat transfer rates shows the characteristics of body shape and variations in posture.     

An overview of the AIRS radiative transfer model

The two main elements of the Atmospheric Infrared Sounder radiative transfer algorithm (AIRS-RTA) are described in this paper: 1) the fast parameterization of the atmospheric transmittances that are used to perform the AIRS physical retrievals and 2) the spectroscopy used to generate the parameterized transmittances. We concentrate on those aspects of the spectroscopy that are especially relevant for temperature and water vapor retrievals. The AIRS-RTA is a hybrid model in that it parameterizes most gases on a fixed grid of pressures, while the water optical depths are parameterized on a fixed grid of water amounts. Water vapor, ozone, carbon monoxide, and methane profiles can be varied, in addition to the column abundance of carbon dioxide.     

EOS MLS forward model polarized radiative transfer for Zeeman-split oxygen lines

This work supplements the Earth Observing System (EOS) Microwave Limb Sounder (MLS) clear-sky unpolarized forward model with algorithms for modeling polarized emission from the Zeeman-split 118.75-GHz O/sub 2/ spectral line. The model accounts for polarization-dependent emission and for correlation between polarizations with complex, 2/spl times/2 intensity and absorption matrices. The oxygen line is split into three Zeeman components by the interaction of oxygen's electronic spin with an external magnetic field, and the splitting is of order /spl plusmn/0.5 MHz in a typical geomagnetic field. Zeeman splitting is only significant at pressures low enough that collisional broadening (/spl sim/1.6 MHz/hPa) is not very large by comparison. The polarized forward model becomes significant for MLS temperature retrievals at pressure below 1.0 hPa and is crucial at pressures below /spl sim/0.03 hPa. Interaction of the O/sub 2/ molecule with the radiation field depends upon the relative orientation of the radiation polarization mode and the geomagnetic field direction. The model provides both limb radiances and the derivatives of these radiances with respect to atmospheric temperature and composition, as required by MLS temperature retrievals. EOS MLS views the atmospheric limb at 118.75 GHz with a pair of linear-cross-polarized, 100-kHz-resolution, 10-MHz-wide spectrometers. The antennas of the associated receivers are scanned to view rays with tangent heights from the Earth's surface to 0.001 hPa. Comparisons of the modeled MLS radiances with measurements show generally good agreement in line positions and strengths, however residuals in the line centers at the highest tangent heights are larger than desired and still under investigation.     

基于MB模型的简化偏振BRDF模型建立与仿真

偏振BRDF模型的计算往往非常复杂,为了简准确地获取伪装目标和背景的反射光偏振度差值,采用特殊值法和理想化方法对Maxwell-Beard BRDF模型中的微面元分布函数和遮蔽函数进行简化,使微面元分布函数较Torrance-Sparrow模型准确,较Maxwell-Beard模型更简单.然后利用Fresnel反射中物体对光线平行分量和竖直分量反射率不同的性质,采用物理理论分析的方法计算得到表示反射过程的Muller矩阵,并建立了其矢量BRDF模型.针对面内反射,利用Matlab对模型进行模拟,仿真结果证明:模型可以描述粗糙表面反射偏振特性.研究结果对研究粗糙表面反射偏振特性的影响因素及伪装目标偏振探测有一定的理论和实践意义.     

基于电路参数模型的辐射电磁干扰噪声预估方法

针对Hubing电流驱动模型中认为电流在辐射线缆中是均一分布的, 幅值和相位保持不变即未考虑辐射线缆共模电流频率效应给辐射电磁干扰噪声预估带来的误差的问题.文中利用电流传输波动特性建立了辐射线缆长度与共模电流波长为同一数量级时的辐射线缆共模电流分布模型, 并设计电路模型进行测试预估.实验结果表明:采用文中方法预估辐射电磁干扰噪声与Hubing电流驱动模型预估方法相比能提高20.12 dBμV/m, 更加接近标准暗室测试结果, 从而为辐射电磁干扰(Electro Magnetic Interference, EMI)测试与分析提供理论依据.     

基于多测量向量模型的极化探地雷达成像算法

针对极化探地雷达( GPR)工作过程中目标成像空间的联合稀疏性,提出了一种基于多测量向量模型的极化探地雷达成像算法。在建立极化探地雷达回波信号模型的基础上,利用各极化通道测量数据的联合稀疏性将各个极化通道的测量数据等效成多测量向量( MMV ),通过多任务贝叶斯压缩感知( MT-BCS)算法对各个极化通道的测量数据进行联合处理从而实现各个极化通道对应的探测场景反射率的重建。基于时域有限差分( FDTD)法的仿真数据处理结果表明所提成像算法在目标位置重建的准确性和背景杂波抑制能力上均优于单测量向量( SMV)模型的极化探地雷达成像算法。     

An analytic BRDF model of canopy radiative transfer and itsinversion

Radiative transfer modeling of the bidirectional reflectance distribution function (BRDF) of leaf canopies is a powerful tool to relate multiangle remotely sensed data to biophysical parameters of the leaf canopy and to retrieve such parameters from multiangle imagery. However, the approximate approaches for multiple scattering that are used in the inversion of existing models are quite limited, and the sky radiance frequently is simply treated as isotropic. This paper presents an analytical model based on a rigorous canopy radiative transfer equation in which the multiple-scattering component is approximated by asymptotic theory and the single-scattering calculation, which requires numerical integration to properly accommodate the hotspot effect, is also simplified. Because the model is sensitive to angular variation in sky radiance, the authors provide an accompanying new formulation for directional radiance in which the unscattered solar radiance and single-scattering radiance are calculated exactly, and multiple-scattering is approximated by the well-known δ two-stream approach. A series of validations against exact calculations indicates that both models are quite accurate, especially when the viewing angle is smaller than 55°. The Powell algorithm is then used to retrieve biophysical parameters from multiangle observations based on both the canopy and the sky radiance distribution models     

EOS MLS cloud ice measurements and cloudy-sky radiative transfer model

A cloud ice retrieval technique is described here using measurements at frequencies near 118, 190, 240, and 640 GHz and 2.5 THz from the Earth Observing System Microwave Limb Sounder on the NASA Aura satellite. Measurement principles, methods for cloud detection, and radiative transfer models for retrieving cloud properties are discussed. The 240-GHz data from high-tangent heights are used to retrieve ice water content at pressures <215 hPa, and the 118-, 190-, 240-, and 640-GHz radiances from low-tangent heights are used to retrieve ice water paths with different penetration depths. Some early Microwave Limb Sounder (MLS) results are highlighted, and the observed cloud signatures are consistent with the expectation from model simulations, in general. The simultaneous measurements from MLS 240 and 640 GHz radiometers contain useful information on particle sizes. There are significant cloud-induced radiances at 2.5 THz, despite strong attenuation from the atmosphere. Cloud-scattering signatures are polarized at 122 GHz, but the polarization differences are typically less than 10% of the total cloud-induced radiance.     

通用大气辐射传输软件(CART)及其应用

大气光谱透过率和背景辐射的计算在诸如大气遥感、光电工程等领域有重要应用。根据所提出的中分辨率大气分子吸收快速计算方法、大气气溶胶衰减计算方法、大气多次散射快速算法,研制了一套通用大气辐射传输计算软件(CART),该软件可根据大气参数快速计算可见光到远红外波段的大气光谱透过率和大气背景辐射,光谱分辨率1 cm-1,覆盖可见光到远红外波段。介绍了该软件的计算模型、主要功能和计算实例、部分实际验证结果以及应用领域。CART在目标辐射特性测量的大气修正、光电设备的设计和性能评估将有广泛的应用。     

Indoor wide-band polarimetric measurements on maize plants: a study of the differential extinction coefficient

A study of the wide-band polarimetric backscatter of maize plants, measured in laboratory conditions, is presented. The backscatter slant-range profiles in both linear (H-V) and Pauli basis manifest a higher extinction coefficient in the vertical channel due to the dominant vertical orientation of the structure of corn plants. The difference between the horizontal and vertical range profiles as the wave penetrates into the volume is employed to retrieve the differential extinction coefficient. In addition, the polarimetric target decomposition, as proposed by Cloude and Pottier, is used to obtain range profiles of alpha, entropy, and anisotropy. All these results reveal important features to be accounted for in the retrieval of the biophysical parameters of agricultural crops by means of polarimetric synthetic aperture radar interferometry.     

极化SAR遥感中森林特征的提取

提出了极化散射矩阵总功率、极化熵、相似性参数的组合表达式。通过特征值分析可得该组合表达式的最优系数。该表达式对森林地区的特征敏感,所以可用来检测森林地区。使用中国天山地区的极化SAR数据,验证了所提方法是有效的。     

A three-component scattering model for polarimetric SAR data

An approach has been developed that involves the fit of a combination of three simple scattering mechanisms to polarimetric SAR observations. The mechanisms are canopy scatter from a cloud of randomly oriented dipoles, evenor double-bounce scatter from a pair of orthogonal surfaces with different dielectric constants and Bragg scatter from a moderately rough surface. This composite scattering model is used to describe the polarimetric backscatter from naturally occurring scatterers. The model is shown to describe the behavior of polarimetric backscatter from tropical rain forests quite well by applying it to data from NASA/Jet Propulsion Laboratory's (JPLs) airborne polarimetric synthetic aperture radar (AIRSAR) system. The model fit allows clear discrimination between flooded and nonflooded forest and between forested and deforested areas, for example. The model is also shown to be usable as a predictive tool to estimate the effects of forest inundation and disturbance on the fully polarimetric radar signature. An advantage of this model fit approach is that the scattering contributions from the three basic scattering mechanisms can be estimated for clusters of pixels in polarimetric SAR images. Furthermore, it is shown that the contributions of the three scattering mechanisms to the HH, HV, and VV backscatter can be calculated from the model fit. Finally, this model fit approach is justified as a simplification of more complicated scattering models, which require many inputs to solve the forward scattering problem     

Four-component scattering model for polarimetric SAR image decomposition

A four-component scattering model is proposed to decompose polarimetric synthetic aperture radar (SAR) images. The covariance matrix approach is used to deal with the nonreflection symmetric scattering case. This scheme includes and extends the three-component decomposition method introduced by Freeman and Durden dealing with the reflection symmetry condition that the co-pol and the cross-pol correlations are close to zero. Helix scattering power is added as the fourth component to the three-component scattering model which describes surface, double bounce, and volume scattering. This helix scattering term is added to take account of the co-pol and the cross-pol correlations which generally appear in complex urban area scattering and disappear for a natural distributed scatterer. This term is relevant for describing man-made targets in urban area scattering. In addition, asymmetric volume scattering covariance matrices are introduced in dependence of the relative backscattering magnitude between HH and VV. A modification of probability density function for a cloud of dipole scatterers yields asymmetric covariance matrices. An appropriate choice among the symmetric or asymmetric volume scattering covariance matrices allows us to make a best fit to the measured data. A four-component decomposition algorithm is developed to deal with a general scattering case. The result of this decomposition is demonstrated with L-band Pi-SAR images taken over the city of Niigata, Japan.     

基于简缩极化数据的三分量分解模型

基于部分极化波的二分理论,提出了一种针对简缩极化数据的三分量分解模型。该模型将简缩极化数据的Jones相干矩阵分解成表面散射、偶次散射和体散射三种散射机制Jones相干矩阵之和,进一步得到这三种散射机制各自的散射功率。选取德国根多夫市普拉特灵(Plattling)地区的TerraSAR-X全极化数据生成简缩极化数据,用提出的三分量分解模型对得到的简缩极化数据进行分解,并将分解结果与全极化数据的Pauli分解结果进行对比。实验结果表明:提出的简缩极化数据三分量分解模型能够很好地描述表面散射和体散射的散射行为。但是,相比全极化数据的分解结果,提出的模型高估了体散射分量,导致偶次散射分量偏小,这个问题需要进一步的研究来解决。     

基于多平台的微远程组态监控模型

伴随着工控领域规模的日益壮大,移动端智能设备也更多地参与到工业自动化中来。人们对组态监控的实时性和移动设备的支持程度有着越来越高的要求。然而传统组态软件,体积臃肿、安装配置复杂、远程操控能力差、系统整合能力差,并且对操作系统有着严格的约束。针对以上诉求及问题,参考浏览器/服务器体系结构,在原有基础上进行改良,设计了一款体验友好的多平台支持的微远程组态监控模型,解除了用户的空间限制,让所有支持移动互联网访问的终端都可以进行远程监控,具有重大的工程意义。