Deriving glacier border information based on analysis of decorrelation in SAR interferometry

Variations of glaciers are important parameters for monitoring glacial change. Although optical remote sensing method can extract variations of glaciers effectively and accurately in cloudless regions, these variations are difficult to extract in cloudy conditions and bad weather. In this paper, a new method is presented, based on the decorrelation of repeat SAR interferometry, to extract the variations of glaciers. This method uses the decorrelation of the inland glacier＇s surface to extract the variation of glacier by comparing the coherence of the glacier and land cover in threshold values. For validation of this method, we compared classification results with that derived from TM images. An accuracy of better than 89% can be achieved if we consider the classification result from TM image as the ground truth. Results show that this method provides an effective way to identify icy areas from the coherent image.     

航天器交会对接远程导引段的精密轨道确定

探讨了CEI技术在飞船交会对接远程导引段的高精度定位与监控的能力,采用了差分相位延迟和相位延迟率为观测量进行轨道解算,仿真结果表明可满足远程导引段的精度指标。     

差分干涉雷达遥感在地质学中的应用研究

雷达差分干涉测量是当前雷达遥感的热点研究领域，对地质学特别是地震、火山、大地构造的研究具有极其重要的意义。文章对差分干涉雷达遥感的原理及具体实现进行了深入研究，并分析了差分干涉测量结果的误差，郑重阐述了差分干涉雷达遥感在地震、地表形变测量、火山监测、板块构造研究中的应用。     

基于TerraSAR-X卫星数据的内孤立波参数和海表流速信息提取的探索研究

本文利用TerraSAR-X(TSX)卫星于2010年4月22日在南海东沙岛附近海域获取的数据进行海洋内孤立波动力要素和海表流速信息的提取研究。基于TSX数据的后向散射强度信息,利用经验模态分解法得到内孤立波半波宽度,再利用两层模型法和参数化法计算得到内孤立波振幅和相速度。反演结果显示,利用参数化方法得到的振幅(约21～39 m)和两层模型法得到的相速度(约1.07 m/s)与历史实测资料较为一致。进而利用TSX的顺轨干涉数据获取研究海域内的多普勒速度,再分别采用M4S模型法和直接分离法处理,进而提取海表流速。结果显示,两种方法得到的海表流速的全场平均值较为一致,均为1.10 m/s左右。M4S模型法对流速最大值的改变量较大而直接分离法对流速最小值的改变量较大。M4S模型对内孤立波波峰线区域海表流速的修正大于无内孤立波的海域。最后,基于KdV方程计算得到内孤立波引起的表面流的流速约为0.28 m/s,对反演出的海表流速贡献占比23%。     

Observational evidence for massive black holes in the centers of active galaxies

Naturally occurring water vapor maser emission at 1.35 cm wavelength provides an accurate probe for the study of accretion disks around highly compact objects, thought to be black holes, in the centers of active galaxies. Because of the exceptionally fine angular resolution, 200 microarcseconds, obtainable with very long baseline interferometry, accompanied by high spectral resolution, <0.1 km s^-1, the dynamics and structures of these disks can be probed with exceptional clarity. The data on the galaxy NGC 4258 are discussed here in detail. The mass of the black hole binding the accretion disk is 3·9 × 10⁷ M_⊙. Although the accretion disk has a rotational period of about 800 years, the physical motions of the masers have been directly measured with VLBI over a period of a few years. These measurements also allow the distance from the earth to the black hole to be estimated to an accuracy of 4 per cent. The status of the search for other maser/black hole candidates is also discussed.     

传统多波束系统与具有相干特点的多波束系统的研究

传统多波束系统和具有相干特点的多波束系统(以下简称相干多波束系统)在波束的形成原理上分别运用了束控法和相干法两种不同的方法。相干法在波束的形成原理上已经没有了传统的“波束”的概念,它在获取数据量上的绝对优势使相干多波束系统在数据密度、准确度以及分辨率上较之传统多波束系统都有较大的提高。这些特性使得相干多波束系统在测深方面尤其是浅水测深上将发挥越来越大的作用。     

C-band和L-band雷达干涉数据西部冰川区域相干性对比分析

干涉雷达相干性问题是制约利用干涉方法提取中国内陆冰川相关参数的重要原因.本文在理论分析干涉空间失相干因素的基础上,从垂直基线、地面坡度和波长3个方面对比了雷达干涉数据在内陆冰川表面的干涉特性.以中国西部典型的内陆冰川(冬克玛底冰川)为研究区域,采用C-band的ENVISAT/ASAR和L-band的ALOS/PALSAR数据,对比分析二者在冰川区域相干性的差别,并给出了量化结果.研究表明,相比于C-band雷达干涉数据, L-band雷达干涉数据在内陆冰川区域具有更强的抗失相干的能力,更适合于内陆冰川相关参数的提取.     

TanDEM-X系统相对测高性能分析

针对TanDEM-X卫星计划,重点分析其在一个轨道周期内的测高性能的变化情况.首先从建立双星HELIX构形的HILL.方程出发,分析了一个轨道周期内直接影响干涉测高的有效基线,包括顺轨和交轨基线的影响,然后讨论了系统相关系数及其对干涉相位误差的影响,通过建立相对高程误差模型,进一步分析了系统相对高程精度.最后计算机仿真结果验证了分析的正确性.