Ionospheric Artifacts in Simultaneous L-Band InSAR and GPS Observations
Ionospheric Artifacts in Simultaneous L-Band InSAR and GPS Observations
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DOI：
10.1109/tgrs.2011.2164805
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发表时间：
2012-04
影响因子：
8.2
通讯作者：
Jingyi Chen;H. Zebker
中科院分区：
文献类型：
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作者：
Jingyi Chen;H. Zebker
干涉合成孔径雷达（InSAR）图像中的相位伪影经常降低地形相位和相关特征的可解释性。通常，这些失真归因于两个不同SAR采集时间的空间可变电离层传播延迟。我们在这里展示了来自冰岛、加利福尼亚和夏威夷的l波段InSAR数据。加利福尼亚和夏威夷的干涉图没有显示出明显的电离层伪影，而冰岛的干涉图在方位角方向上显示出最大3个像素的错配，这导致了InSAR图像中严重的相位去相关伪影。我们将干涉图中看到的复杂像素的错配与全球定位系统（GPS）数据观测到的电离层总电子含量（TEC）的梯度联系起来，并证实冰岛干涉图中的相位伪影确实是由于电离层传播的色散而不是其他去相关因素，如中性大气延迟。本文提出了一种利用双频GPS载波相位数据在合成孔径长度尺度下测量空间TEC变化的方法。我们使用从电离层观测数据或GPS载波相位数据本身获得的低分辨率电离层参考来解决GPS数据的模糊性。GPS观测直接显示了电离层的变化水平，GPS观测的空间TEC梯度预测了所有三个区域干涉图中复杂像元的错配。这种对图像伪影原因的确认表明，只要传感器测量沿雷达带的TEC变化，就可以仅从InSAR数据进行常规校正。
Phase artifacts in interferometric synthetic aperture radar (InSAR) images frequently degrade the interpretability of the phase and correlation signatures of terrain. Often, these distortions are attributed to spatially variable ionospheric propagation delays at two different SAR acquisition times. We present here L-band InSAR data from Iceland, California, and Hawaii. The California and Hawaii interferograms show no significant ionospheric artifacts, while the Iceland interferogram shows a maximum misregistration of three pixels in the azimuth direction, which leads to severe phase decorrelation artifacts in the InSAR image. We relate the misregistration of complex pixels seen in the interferograms to the gradient of the ionospheric total electron content (TEC) observed by global positioning system (GPS) data and confirm that indeed the phase artifacts in the Iceland interferogram are due to dispersive ionospheric propagation rather than other decorrelation factors such as neutral atmospheric delays. We develop a method to measure the spatial TEC variation at synthetic aperture length scales using dual-frequency GPS carrier phase data. We solve for the GPS data ambiguities using a low-resolution ionosphere reference derived from either available ionospheric observations or the GPS carrier phase data themselves. GPS observations show directly the level of ionospheric variability, and the spatial TEC gradient as observed by GPS predicts the misregistration of complex pixels in interferograms in all three areas. This confirmation of the cause of the image artifacts suggests that they can be routinely corrected from the InSAR data alone, provided that the sensor measures the change in TEC along the radar swath.