Towards Better InSAR Event Detection: Modeling Atmospheric Artifacts

目前正在建立一个高分辨率天气“后播”系统，用于模拟SAR场景获取时的大气，以减轻大气水蒸气对InSAR变形图的影响。相位延迟屏是由大气分析生成的，用于校正干涉图像，改善InSAR叠加结果，并将其作为约束条件推进PSInSAR变形映射技术。这项技术的发展主要集中在两个研究区域，代表了典型的气象条件、地球物理信号源和雷达反射环境：华盛顿的圣海伦斯火山和南加州的洛杉矶。这种估算和降低大气噪声的新方法的发展将提高InSAR作为一种操作监测工具的有效性，扩展使用InSAR进行调查的可能性，并提高该技术的分辨率。大气中水汽分布变化引起的差分延迟是SAR干涉测量技术的最大噪声源。大气效应可以覆盖所有波长，幅度可达几厘米甚至更大。大量SAR场景的叠加提高了InSAR的信噪比，但这需要大量的数据，并且大气伪影可能仍然存在。基于“持久”散射体（PSInSAR）的令人兴奋的新一代InSAR时间序列分析和处理技术也受到从干涉图中明确去除大气水汽异常的困难的限制。通过直接模拟每次捕获时的大气，产生了对视距大气相位延迟的独立估计。这些可以从InSAR图像中去除，提高大地测量信号的信噪比，允许使用更少的场景进行分析，减少必要的数据量，提高非线性事件的分辨率。它们还提供了一种独立的方法来确认PSInSAR处理中的大气相位筛选估计，并通过协助客观分离大地测量和大气信号来改进PSInSAR变形制图技术。在处理InSAR数据时，通常会对SAR卫星的轨道参数进行细化，这也将减轻一个相关的问题。轨道误差在干涉图中表现为线性相位斜坡，然而长波长的天气模式可能引起类似的特征。这两种伪影来源之间的模糊性可能导致处理过程中不适当的纠正步骤，可能掩盖真正的长波地面运动信号。所产生的天气分析正在通过地球观测和联阿援助办事处公开提供，以便进一步研究InSAR处理技术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.