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首页> 外文期刊>IEEE Transactions on Geoscience and Remote Sensing >A noise model for estimated synthetic aperture radar look cross spectra acquired over the ocean
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A noise model for estimated synthetic aperture radar look cross spectra acquired over the ocean

机译：用于估计海洋上获取的合成孔径雷达视交叉谱的噪声模型

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摘要

It is well known that look cross spectra processed from synthetic aperture radar (SAR) contain valuable information on ocean waves. With the launch of the European satellite ENVISAT, SAR look cross spectra (SLCS) have become available on an operational basis. Activities therefore exist at different European weather centres to use the data for assimilation into numerical wave models. Furthermore there is scientific interest in SLCS, e.g., concerning the estimation of the phase speed of ocean waves. For the estimation of ocean wave parameters, it is important to have information about the accuracy of SLCS. In this paper, errors of estimated SLCS due to SAR image speckle, spectral estimation errors, and image pattern decorrelation associated with ocean wave motion are analyzed. A probability model is proposed for the estimated SLCS based on the respective cross-spectrum coherence. The model is used to calculate signal-to-noise ratios and confidence limits for the SLCS phase and magnitude, as well as the real and imaginary part. The coherence is factored into a component describing look decorrelation due to SAR image speckle and a second factor describing the effect of sea surface motion. It is shown that the ocean-wave-dependent decorrelation can be simulated using existing nonlinear integral transforms for the look variance spectrum and the SLCS. The decorrelation effect associated with speckle noise is related to SAR system parameters, e.g., the spatial SAR resolution. The probability model is used to investigate the optimal choice of look processing parameters like the look separation time. A statistical analysis based on a global dataset of a reprocessed dataset of European Remote Sensing 2 satellite SLCS is presented confirming the applicability of the probability model. The implications of the results for the retrieval of two-dimensional wave spectra from SLCS are summarized. Possible future applications of the model like, for example, the investigation of the turbulent air flow over waves, are discussed.
机译：众所周知，合成孔径雷达（SAR）处理的外观交叉光谱包含有关海浪的宝贵信息。随着欧洲卫星ENVISAT的发射，SAR视交叉谱（SLCS）已在运营中可用。因此，在不同的欧洲气象中心存在着将数据同化为数值波动模型的活动。此外，例如，关于海浪的相速度的估计，在SLCS中存在科学兴趣。对于海浪参数的估计，掌握有关SLCS精度的信息非常重要。在本文中，分析了由SAR图像斑点引起的估计SLCS的误差，光谱估计误差以及与海浪运动相关的图像模式去相关。根据各自的频谱间的相干性，为估计的SLCS提出了一个概率模型。该模型用于计算SLCS相位和幅度以及实部和虚部的信噪比和置信限。相干性被分解成一个描述因SAR图像斑点而引起的外观去相关的分量，以及一个描述海面运动影响的第二个因子。结果表明，可以使用现有的非线性积分变换对视差谱和SLCS进行海浪相关的去相关模拟。与斑点噪声相关的去相关效应与SAR系统参数有关，例如空间SAR分辨率。概率模型用于调查外观处理参数（如外观分离时间）的最佳选择。提出了基于欧洲遥感2卫星SLCS再处理数据集的全局数据集的统计分析，确认了概率模型的适用性。总结了结果对从SLCS检索二维波谱的意义。讨论了该模型可能的未来应用，例如研究波浪上的湍流。

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