双峰海浪谱的SAR图像交叉谱仿真研究

由6参数双峰频谱和cos-2s型分布函数得到了双峰海浪方向谱的波数谱形式,并利用海浪谱到合成孔径雷达(Synthetic Aperture Radar,SAR)图像交叉谱的非线性转换关系,对双峰海浪谱的SAR图像交叉谱进行了仿真,分析了不同海浪参数和SAR平台参数对SAR图像交叉谱的影响,并与SAR图像谱进行了比较。     

全极化合成孔径雷达海浪遥感方法

提出了一种利用全极化真实孔径雷达测量方位方向和距离方向海浪斜率的新方法,该方法不同于极化方向角估计海浪方位向斜率方法,利用两种线极化图像信息将有关弱极化项剔除(流体动力学调制),获得仅包含倾斜项和极化调制项的雷达成像公式。利用机载SAR取代真实孔径雷达进行海浪反演,获得了与浮标致的结果。另外,在速度聚束模式情况下,推导了双极化合成孔径雷达图像谱同海浪谱的非线性变换关系。     

SAR海浪方向谱的Monte Carlo仿真

利用Longuet-Higgins线性海浪模型和JONSWAP海浪谱来表示海浪方向谱。在Bragg波散射模型的假设下,推导了海浪谱与SAR图像谱之间的映射变换,它适用于线性海浪的成像范围。采用Monte Carlo方法,可产生具有随机性的海浪方向谱。对于时不变的海面来讲,该方法具有计算效率适中的特点。仿真结果表明,海浪谱与SAR图像谱之间存在着谱的畸变、谱的分裂和方位向谱的移位等特点。     

极化合成孔径雷达测量海浪的研究

描述了极化合成孔径雷达海浪成像过程。提出了一种极化雷达反演海浪方向谱的方法,该方法利用合成孔径雷达图像谱与海浪方向谱之间简单的线性关系和最优方法反演得到海浪方向谱,并将结果与现场资料进行了比较。经过对同一海区机载雷达P、L、C 3个波段的图像进行反演,其方向谱相当一致,而且有效波高和波向与实测数据吻合相当好。     

SAR探测水下运动物体波浪尾迹的模拟研究

水下运动物体可以在海面产生波浪,这种波浪与海洋表面波相互作用改变了海浪谱的高低频分布而形成波浪尾迹。将这样的波-波相互作用处理为对背景海浪谱的扰动,利用海面微波散射的二尺度模型,分析波浪尾迹对雷达散射系数的影响,并给出相应的数值计算模型;对水下不同运动状态物体的波浪用汇源分布法计算出波面函数,将它们分别与一些特定海况的海浪波面函数叠加,并对之进行微波后向散射测量仿真计算,给出波浪尾迹的SAR(Synthetic Aperture Radar、合成孔径雷达)探测图像;再利用二维谱分析技术对模拟SAR图像进行处理,提取波浪尾迹信息。初步结果表明,SAR探测下运动物体是可行的。
     

合成孔径雷达舰船航迹成像模型及其数字仿真

该文描述了一种合成孔径雷达(SAR)Kelvin舰船航迹成像的数学模型，该模型考虑了流体粘性和海洋背景的影响，在一定条件下对Kelvin舰船航迹的合成孔径雷达成像进行了计算机数字仿真。仿真结果较好地反映了航迹的表面分布情况，为研究舰船航迹在合成孔径雷达图像中的成像机理提供了理论分析依据。     

极化SAR图像地物分类方法综述

极化合成孔径雷达(Polarimetric Synthetic Aperture Radar, PolSAR)是一种微波成像雷达, 它不受天气、光线以及云层的影响, 能够实现全天时、全天候的成像. 因此, 极化SAR图像已经成为遥感图像地物分类的主要数据源之一. 本文从技术方法的角度出发, 论述了近年来国内外极化SAR图像地物分类的方法及应用, 从技术原理、实验效果等方面进行介绍, 并对极化SAR图像地物分类的发展趋势进行分析.     

水下航行器测量海浪方向分布研究

研究水下优化测量海浪信息问题,由于海浪谱准确实时测量比较难,针对传统的海浪方向谱测量方法均需要大量的仪器设备和长时间的数据测量处理的不足,为提高测量效率,提出一种通过水下航行器测量海浪方向分布的方法.首先利用水下航行器携带的流速测量设备得到所经过海域的三维流速序列,通过计算三维流速的互谱和自谱,得到描述海浪方向分布的傅立叶系数,利用系数推算出各个频率波浪的主波向角,用海浪能量密度加权处理后得到整个海域内海浪的主波向角进行仿真.仿真结果表明了不同海浪参数下估计结果,验证了方法的有效性.改进方法不仅可以获取某一特定地点的海浪方向谱,还可以随水下航行器的位置变化准确实时获取相应海区的海浪方向谱,为设计提供了依据.     

合成孔径雷达地面动目标检测方法研究

分析了合成孔径雷达(SAR)地面动目标检测的特点,研究了几种动目标检测方法,包括:移位相位中心天线(DPCA)方法、沿迹干涉(ATI)方法、空时自适应(STAP)方法以及解卷积方法,画出了部分方法的检测流程图,分析了每种方法的特点,最后给出了采用ATI方法检测时动目标参数计算方法。     

旋翼无人机载SAR杠杆臂误差补偿算法

研究旋翼无人机作为合成孔径雷达(Synthetic Aperture Radar,SAR)的移动平台,为了提高机动灵活性,但是同样也会带来剧烈的飞行扰动.通常借助于全球定位系统(Global Positioning System,GPS)实时获取雷达位置是常用的机载SAR运动补偿方法,但是GPS天线和雷达天线的安装位置在空间上并不重合,而二者之间的空间位置差被称为杠杆臂,杠杆臂的存在使得GPS测量结果并不能真实表征雷达天线位置,直接使用GPS测量结果将使得运动补偿出现偏差.提出的杠杆臂补偿方法,能够根据GPS测量结果实时解算雷达天线位置,从而使用更为准确的雷达运动参数补偿误差,获取高精度高质量的SAR图像.从旋翼无人机运动模型入手,分析了杠杆臂误差对成像的影响,并给出了依据GPs和姿态数据演算的雷达天线位置.最后,在仿真的基础上引入了实测的旋翼无人机的运动数据,验证了改迸算法的有效性.     

Interferometric SAR imagery of a monochromatic ocean wave in the presence of the real aperture radar modulation

Abstract

The model which allows one to simulate the Synthetic Aperture Radar (SAR) and the along track Interferometric SAR (INSAR) imagery of a monochromatic ocean wave is presented. The model accounts for the effects of the real aperture radar (RAR) modulation of the radar backscatter cross-section. The comparison of the SAR and the INSAR imagery of the wave system under consideration is carried out and the performance of the two imaging systems is studied under various operational conditions. The results of the study indicate that the interferometric SAR is less sensitive to the RAR modulation as compared lo the regular SAR. This fact further augments the assertion that INSAR has considerable advantages over SAR in its potential of providing quantitative information about the ocean wave lengths, directions and amplitudes     

新型多基线DInSAR地表形变监测技术研究动态

合成孔径雷达干涉测量（InSAR）是一项广泛采用的雷达遥感测量技术,可以获取大区域、长时间、毫米级的地表形变监测,是SAR图像应用研究的热点。从InSAR技术监测地表形变时面临的问题出发,分析了近年来多基线DInSAR方法的新进展,论述了相干目标算法\,分布目标算法及SAR层析成像技术等在监测地表运动时的原理及技术应用,详细讨论了DInSAR地表形变监测由二维参数研究发展至三维、四维空间,由城区发展至广阔非城区地表监测的发展趋势。     

一种面向雷达工作流程的星载合成孔径雷达回波模拟

合成孔径雷达系统模拟是雷达系统设计最有效、最经济的检测方法,它可对雷达的功能、雷达的结果通过计算机进行模拟,改变参数就可获得不同地物、不同雷达参数、不同雷达模式的模拟结果。与设备仿真相比,它能快速实现并且不需高昂的成本。介绍了一种星载合成孔径雷达模拟方法,它以实际雷达信号的流程为依据,模拟雷达各部分的工作,更接近真实的模拟合成孔径雷达的回波。     

Radar imaging of Kelvin arms of ship wakes

The wave pattern generated by a moving ship is formed by two dominant features: the turbulent wake and a 'V'-shaped pattern trailing the ship, consisting of the two Kelvin arms. In this paper we investigate the radar imaging mechanism of Kelvin arms, which are formed by the cusp waves. A composite surface model for the radar backscattering at the ocean surface is used. The radar signatures of Kelvin arms can be attributed to tilt and hydrodynamic modulation of Bragg waves by the cusp waves. The proposed model allows the computation of the normalized radar backscattering cross-section (NRCS) as a function of radar frequency, polarization, incidence angle, wind speed and direction, and wavelength, direction, and slope of the cusp waves. By using this imaging model, radar signatures of cusp waves are calculated for several spaceborne Synthetic Aperture Radars (SARs): (1) the SEASAT L-band HH-polarized SAR, (2) the ERS-1/-2 VV-polarized SAR, (3) the RADARSAT C-band HH-polarized SAR, and (4) the X-, C- and L-band multipolarization SARs of the Space Radar Laboratory flown on the space shuttle during the SIRC/X-SAR mission in 1994. The results of the simulations are compared with SEASAT and SIR-C/X-SAR imagery of ship wake patterns. It is shown that the dependence of the observed radar signatures of Kelvin arms on radar look direction is consistent with the proposed imaging theory and that the measured relative mean NRCS values induced by Kelvin arms can be fairly well reproduced by the proposed model. The simulations indicate that ship wake signatures should be more clearly visible on SEASAT L-band SAR than on ERS-1/-2 or RADARSAT C-band SAR images. The radar signatures of Kelvin arms are strongest at low wind speeds and are not very sensitive to wind direction.     

合成孔径与实孔径雷达谱域成像算法对比分析

讨论了合成孔径雷达(Synthetic aperture radar,SAR)和实孔径雷达(Real aperture radar,RAR)一维扫描方式下的谱域成像实现问题.文中从SAR和RAR扫描下的波数域波散关系入手,分析了这两种扫描方式下的谱域填充区域和成像分辨率,指出了二者的异同,导出了相应的成像算法.单目标和组合目标的雷达成像仿真实验验证了两种扫描方式下成像算法的有效性和理论分析结果.     

合成孔径雷达图像内波参数提取方法研究

给出了利用傅立叶谱分析和小波分析提取合成孔径雷达(SAR)图像中内波波长和波向参数的方法,并以台湾西南部附近海域1995年6月26日的ERS-1 SAR图像为例,作了内波参数提取实例研究。结果表明,两种方法能较好地提取所需参数,并有较好的一致性。同时还解决了谱分析法确定波向过程中的180°模糊问题。     

Seasat—A 25-year legacy of success

Thousands of scientific publications and dozens of textbooks include data from instruments derived from NASA's Seasat. The Seasat mission was launched on June 26, 1978, on an Atlas-Agena rocket from Vandenberg Air Force Base. It was the first Earth-orbiting satellite to carry four complementary microwave experiments—the Radar Altimeter (ALT) to measure ocean surface topography by measuring spacecraft altitude above the ocean surface; the Seasat-A Satellite Scatterometer (SASS), to measure wind speed and direction over the ocean; the Scanning Multichannel Microwave Radiometer (SMMR) to measure surface wind speed, ocean surface temperature, atmospheric water vapor content, rain rate, and ice coverage; and the Synthetic Aperture Radar (SAR), to image the ocean surface, polar ice caps, and coastal regions. While originally designed for remote sensing of the Earth's oceans, the legacy of Seasat has had a profound impact in many other areas including solid earth science, hydrology, ecology and planetary science.     

Simulation of ship wakes image by an along-track interferometric SAR

A mathematical model that allows simulations of the image of waves in ship wakes by either regular or interferometric airborne Synthetic Aperture Radar (SAR or INSAR) is described. The three-component velocity field induced at the ocean surface by a moving ship serves as the input to the model. The simulations take into account the effect of temporal variations of the wave field in the wake on the INSAR imaging by the velocity bunching mechanism. The model also accounts for the scanning distortion of the image. The developed algorithm allows study of the visibility of the ship wave wake by a regular SAR or by INSAR for arbitrary imaging parameters, as well as for different ship sizes and ship velocity vectors relative to the platform flight track. Various patterns of ship wake images obtained by numerical simulations are presented.