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海洋微波散射模型相比于以经验统计建立的地球物理模式函数具有不受特定微波频率限制的优势。组合布拉格散射模型和几何光学模型形成了复合雷达后向散射模型。利用南海北部气象浮标2014年海面风速风向实测值作为散射模型输入,分别比较了复合雷达后向散射模型与RADARSAT-2卫星C波段SAR、HY-2A卫星Ku波段微波散射计的海面后向散射系数,偏差分别为(?0.22±1.88) dB (SAR)、(0.33±2.71) dB (散射计VV极化）和(?1.35±2.88) dB (散射计HH极化);以美国浮标数据中心(NDBC)浮标2011年10月1日至2014年9月30日共3年的海面风速、风向实测值作为散射模型输入,分别比较了复合雷达后向散射模型与Jason-2、HY-2A卫星Ku波段高度计海面后向散射系数,偏差分别为(1.01±1.15) dB和(1.12±1.29) dB。中等入射角和垂直入射下的卫星传感器后向散射系数观测值与复合雷达后向散射模型模拟值比较,具有不同的偏差,但具有相同的海面风速检验精度,均方根误差小于1.71 m/s。结果表明,复合雷达后向散射模型可模拟计算星载SAR、散射计和高度计观测条件下的海面雷达后向散射系数,且与CMOD5、NSCAT-2、高度计业务化海面风速反演的地球物理模式函数的计算结果具有一致性;复合雷达后向散射模型可用于微波遥感器的定标与检验、海面雷达后向散射的模拟。 相似文献
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论文首先从理论上简要阐述了星载海洋高度计海面回波的散射机理和回波信号后向散射模型;其后,利用Matlab数学工具,通过对我国＂神州四号＂飞船下传的大量高度计观测数据进行IQ采样数据提取、数据处理以及统计分析,进行了星载海洋高度计海面回波信号的统计特性分析与研究. 相似文献
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浅海水下地形的SAR遥感仿真研究 总被引：2，自引：0，他引：2
结合连续性方程和布拉格后向散射模型,在准一维简化浅海水下地形情况下,建立了浅海水下地形SAR海面相对后向散射强度仿真模型,将浅海水下地形区域的SAR海面后向散射强度的相对变化与大尺度背景流场、海面风场和雷达系统参数等联系起来.海上实验和研究结果表明,浅海水下地形的SAR成像主要由通过受水下地形影响的海表层流场对海表面风引起的微尺度波的水动力调制而获取浅海水下地形信息,其中潮流与水下地形的相互作用过程改变海表层流场,变化的海表层流与海表面微尺度波之间的相互作用改变海表面波的空间分布,雷达波与海表面波之间的相互作用决定雷达海面后向散射强度.因此SAR图像中浅海水下地形或水深信息量的多少不仅与海表层流场和海面风速有关,而且与雷达工作波段、雷达波束入射角和极化方式也密切相关.认为由水下地形变化引起的缓慢变化的表层流场中海表面定常微尺度波谱能量密度的变化满足波作用量谱平衡方程;而在波数空间中,海表面微尺度波谱的成长过程也可以用波数谱平衡方程描述,在此基础上,得出了海表面波高频谱(毛细-重力波)形式的解析表达式.众所周知,浅海水下地形信息是由于水下地形影响下SAR海面后向散射强度与背景海面后向散射强度的相对差异而在SAR图像上的呈现,从而在建立浅海水下地形SAR海面相对后向散射强度仿真模型的基础上,仿真计算了浅海水下地形SAR海面相对后向散射强度相对于海表层流场、海面风场等海况参数和SAR工作波段、SAR波束入射角、极化方式等雷达系统参数的数值仿真结果,分析得到了有关浅海水下地形SAR海面相对后向散射强度的特征和SAR浅海水下地形遥感的最佳海况参数与最佳雷达系统参数,为研究和开展SAR浅海水下地形遥感研究提供了有价值的参考. 相似文献
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HY-2A卫星雷达高度计海面高度测量分析与评估 总被引：1，自引：0，他引：1
HY-2A卫星是我国首颗自主海洋动力环境卫星,已连续运行6年多。卫星上搭载的主载荷雷达高度计能够实现全天候、全天时全球海面高度、有效波高和海面风速的观测,这些观测数据已经广泛用于海洋防灾减灾、资源开发和海上安全等领域。为了全面了解HY-2A卫星雷达高度计多年来的整体观测性能,本文选取了2012年10月26日至2017年8月27日间的全部观测数据IGDR产品进行综合评价。通过自交叉和与Jason-2互交叉两种手段对HY-2A卫星雷达高度计测高能力进行评估。计算HY-2A升降轨自交叉点的测高不符值,发现HY-2A卫星雷达高度计在近全球海域内、升降轨高度异常差小于30cm的限制条件下,平均绝对高度误差为5.81cm,高度异常标准差为7.76cm;限制观测区域为南北纬60°范围内、海面高度异常升降轨交叉点处的差小于10cm的情况下,平均绝对误差可达3.95cm,海面高度异常标准差达4.76cm。通过和Jason-2卫星的互交叉,发现在南北纬66°范围内,交叉点高度异常差小于30cm的情况下,HY-2A和Jason-2的海面高度异常平均绝对误差为5.86cm,标准差为7.52cm,如果在该海域内将海面高度异常差限制在10cm内,平均绝对误差和标准差分别达到4.19cm和4.98cm。HY-2A卫星雷达高度计已经达到国际同类卫星雷达高度计测高水平,可以满足海洋科学研究、海洋环流反演等的需求。 相似文献
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卫星雷达高度计正从传统星下点的剖面测量向宽刈幅干涉测量发展,利用卫星观测二维的高分辨率、高精度海面高度正在成为可能,国外研究人员提出SWOT(Surface Water and Ocean Topography)干涉雷达高度计计划和我国新一代海洋科学卫星任务等计划有望实现海洋亚中尺度现象的观测。定标检验是评价卫星观测资料精度和质量的必要工作,传统高度计的定标检验均为基于验潮站、GNSS(Global Navigation Satellite System)浮标、有源定标器等方式的单点比对,难以满足干涉高度计的需求。目前国内外研究人员在干涉雷达高度计的定标检验中采用了全新的技术方案,并已利用机载试验和理论模拟开展了验证工作。对近10 a干涉雷达高度计定标检验的新技术方法进行介绍和总结,希望对我国的干涉雷达高度计卫星定标计划起到借鉴作用。 相似文献
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《Oceanic Engineering, IEEE Journal of》2009,34(3):269-284
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Afif Belkacem Kamel Besbes Jacques Chatillon Manell E. Zakharia 《Oceanic Engineering, IEEE Journal of》2006,31(3):614-627
The paper deals with a new concept of imaging technique based on planar synthetic aperture sonar (P-SAS). P-SAS processing takes advantage of the overlap of both ping-to-ping and track to track footprints to improve the imaging resolution in both directions. After describing the method, its implementation is discussed. The exact implementation [three-dimensional (3-D)] is defined and an approximated and faster approach [2timestwo-dimensional (2-D)] is then proposed. The gain in computation time and the possible loss in performances (resolutions, echo amplitude) are investigated by simulating a simple point target. The point spread function is studied in details. The new concept is finally validated by tank experiments (scale about 100) for both proud and buried target imaging 相似文献
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The testing of a synthetic aperture technique, the ETAM algorithm, is extended and its performance for CW pseudorandom signals and broadband ship noise is examined. The results show the limitations of the technique and are of special interest for operational systems development. In the CW experiments, the transmitted signal was generated with high temporal coherence, and loss of the spatial and temporal coherence of the received signal was introduced only by the medium and the stability of the towed array. In the experiments that included the pseudorandom signal and the ship noise, the temporal coherence of the transmitted signals was deliberately chosen to be poor in order to study the effects and the performance of this algorithm with broadband signals. The related experimental results show that for received signals, which have their segments over the synthesizing period highly cross-correlated, a synthetic aperture array gain was achieved that corresponds to the length of an equivalent fully populated array 相似文献
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《Oceanic Engineering, IEEE Journal of》2009,34(3):294-306
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Two techniques for extracting internal wave signature from airborne synthetic aperture radar (SAR) imagery are presented. The first technique involves the extraction of a single-scan signature and appropriate for the validation of theoretical models which utilize sea truth from a limited area as input. The second technique involves creating a signature by averaging the results from a number of single scans within the same scene and is appropriate for trend analyses. The utility of both techniques is illustrated using internal wave signatures present in a multifrequency, airborne SAR data set 相似文献
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It is shown that azimuthal ambiguities are not eliminated by the nulls of a sonar (or radar) beam pattern and have a definite influence on image quality. In synthetic aperture systems that are strongly limited in spatial sampling, particularly in ocean borne synthetic aperture sonar (SAS) and spaceborne synthetic aperture radar (SAR), azimuthal ambiguities will corrupt the images unless special measures are taken. These azimuthal aliases may be reduced by emphasizing the centermost portion of the available synthetic aperture length, and deemphasizing the endmost portions. This minimizes the effects from synthetic array elements that most strongly contribute to aliases 相似文献
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《Oceanic Engineering, IEEE Journal of》2009,34(3):205-206
The eight papers in this special issue focus on synthetic aperture sonar. The focus is on signal processing and performance characterization for synthetic aperture imaging sonars, with emphasis on systems that operate in stripmap mode--a monostatic approach utilizing broadside beams, and which represents the majority of designs currently seeing practical application. 相似文献
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Despite their potential ability to produce highly resolved images of the seabed, synthetic aperture sonars are not widely used. The primary reason for this restricted use is that most synthetic aperture systems are based on the radiation and detection of short-duration modulated pulses. Due to the low speed of sound in water, the pulse repetition frequency is low and so it has been difficult to maintain the required pulse-to-pulse phase coherence. This paper describes a new approach to synthetic aperture sonars based on continuous transmission with some form of frequency modulation. That is, a sonar that transmits and receives continuously but uses some form of frequency coding (in this case a linear frequency sweep) to determine range. Using a continuous transmission frequency modulated sonar it is possible to make a synthetic aperture sonar that can produce coherent apertures many wavelengths long. In addition to the combination of synthetic apertures and continuous transmission frequency modulation, further modifications are suggested to reduce the effect of lateral towfish movement and the effects of medium turbulence resulting in random path-length variations. 相似文献
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与传统的侧扫声纳相比,合成孔径声纳系统具有全覆盖无遗漏扫测,测量范围大、速度快,图像分辨率高等优点。本文介绍我国引进第一套SHADOWS合成孔径声纳系统的技术性能,分析SHADOWS合成孔径声纳系统性能测试情况及实际测量中的应用价值,提出了存在的问题及其对策。 相似文献
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一维综合孔径微波辐射计能够有效提高观测的空间分辨率,其观测入射角通常在0°~55°范围内变化。为了开发适用于一维综合孔径微波辐射计的海面温度反演算法,需要评估其观测亮温对海洋大气环境要素的敏感性。利用海面发射率模型和大气辐射传输模型,构建了适用于一维综合孔径微波辐射计的微波海洋大气辐射传输模式,研究了C波段垂直和水平极化微波辐射亮温在不同入射角下对海洋大气环境要素的敏感性变化情况,并定量计算了相应的敏感系数。结果表明:垂直和水平极化亮温对海洋大气环境要素的敏感性表现出不同的特性。随着入射角的增大,垂直极化亮温对海面温度的敏感性增强,对海面风场的敏感性相对减弱;水平极化亮温则相反。由大气水汽含量和云液态水含量误差引入的垂直和水平极化亮温误差随入射角增大而增大,但是,即使在55°的大入射角下垂直和水平极化亮温误差仍小于0.12 K。对于海面温度反演精度优于1 K的要求,一维综合孔径微波辐射计的测温精度需优于0.6 K。研究结果对于一维综合孔径微波辐射计海面温度反演算法的研究和载荷设计具有一定的理论指导意义。 相似文献