Towards Better InSAR Event Detection: Modeling Atmospheric Artifacts

正在建立一个高分辨率的天气“后报”系统，在合成孔径雷达场景采集时模拟大气，以减轻大气水蒸气对干涉合成孔径雷达变形图的影响。通过大气分析生成相位延迟屏，并将其作为约束条件，用于干涉图像校正，改善干涉合成孔径雷达叠加效果，提高PS干涉合成孔径雷达形变成图技术。该技术正在开发的重点是两个研究领域，代表一个典型的范围内的气象条件，地球物理信号源和雷达反射环境：华盛顿的圣海伦火山，和加州南部的洛杉矶。这种新的方法的发展，估计和减少大气噪声将提高干涉合成孔径雷达作为业务监测工具的有效性，扩大的可能性，调查使用干涉合成孔径雷达，并提高该技术的分辨率。差分延迟所造成的变化，在大气中的水汽分布的SAR干涉（干涉合成孔径雷达）技术的最大噪声源。大气效应可以覆盖所有波长，振幅为几厘米甚至更大。大量SAR场景的叠加提高了干涉合成孔径雷达的信噪比，但这需要大量的数据，大气伪影可能仍然存在。令人兴奋的新一代干涉合成孔径雷达时间序列分析和处理技术基于“持久”散射体（PS干涉合成孔径雷达）也受到从干涉图中明确去除大气水汽异常的困难的限制。通过在每次采集时直接对大气建模，产生视线大气相位延迟的独立估计。这些可以从干涉合成孔径雷达图像中去除，从而提高大地测量信号的信噪比，允许使用较少的场景进行分析，减少必要的数据量，并提高非线性事件的分辨率。它们还提供了一种独立的手段，确认PSInSAR处理中的大气相位屏估计，并通过协助客观分离大地测量和大气信号来改进PSInSAR变形测绘技术。一个相关的问题也将得到缓解，这一问题来自于在处理干涉合成孔径雷达数据时对合成孔径雷达卫星轨道参数进行细化的常见做法。轨道误差在干涉图中表现为线性相位斜坡，然而长波长天气模式可能引起类似的特征。这两个伪影源之间的模糊性可能导致处理中的不适当的校正步骤，可能掩盖真实的长波长地面运动信号。通过GeoEarthScope和UNAVCO向公众提供所作的天气分析，以推动从事干涉合成孔径雷达处理技术工作的其他小组的研究工作。

A high-resolution weather "hindcasting" system to model the atmosphere at the time of SAR scene acquisitions is being established to mitigate the impact of atmospheric water vapor on InSAR deformation maps. Phase delay screen are generated from the atmospheric analyses and used to correct interferometric images, improve InSAR stacking results, and advance the PSInSAR deformation mapping technique by incorporating them as constraints. The technique is being developed by focusing on two study areas, representing a typical range of meteorological conditions, geophysical signal sources and radar reflecting environments: Mount St Helens volcano in Washington, and Los Angeles in southern California. The development of this novel approach for estimating and reducing atmospheric noise will increase the effectiveness of InSAR as an operational monitoring tool, extend the possibilities for investigations using InSAR, and improve the resolution of the technique.The differential delay caused by changes in the distribution of water vapor in the atmosphere is the biggest source of noise for the SAR interferometry (InSAR) technique. Atmospheric effects can range over all wavelengths, with amplitudes of several centimeters or even greater. Stacking of a large numbers of SAR scenes boosts the InSAR signal-to-noise ratio, however this requires large amounts of data, and atmospheric artifacts may still remain. The exciting new generation of InSAR time series analysis and processing techniques based on "persistent" scatterers (PSInSAR) are also limited by the difficulty of unambiguously removing atmospheric water vapor anomalies from interferograms. By directly modeling the atmosphere at the time of each acquisition independent estimates of the line-of-sight atmospheric phase delay are produced. These can be removed from InSAR images, improving the signal to noise ratio for geodetic signals, permitting the use of fewer scenes for analysis, reducing the necessary data volume and improving the resolution of non-linear events. They also provide an independent means of confirming the atmospheric phase screens estimates in PSInSAR processing and improve the PSInSAR deformation mapping technique by assisting in the objective separation of geodetic and atmospheric signals. A related problem that will also be mitigated derives from the common practice of refining orbital parameter for the SAR satellite when processing InSAR data. Orbital errors are manifested in interferograms as linear phase-ramps, however long wavelength weather patterns may induce similar features. The ambiguity between these two sources of artifact could lead to inappropriate corrective steps in the processing, possibly masking real long wavelength ground motion signals. The weather analyses produced are being made publicly available via GeoEarthScope and UNAVCO in order to further research efforts by other groups working on InSAR processing techniques.