星地双基地时序InSAR模型与信号处理方法

Space-Surface Bistatic Time-Series InSAR Model and Signal Processing Method

  • 摘要: 星地双基地合成孔径雷达(Synthetic Aperture Radar, SAR)是利用地面接收系统被动接收星载SAR信号的双基地SAR,具有接收几何灵活的优势。通过时序干涉SAR(Interferometric SAR, InSAR)差分干涉处理,可反演场景高精度形变速率,在地质灾害区域高频次详查方面具有应用潜力。然而,目前尚未有星地双基地时序InSAR的相关研究。本文首先针对星地双基地SAR观测几何特点,建立了星地双基地时序InSAR测量模型。其次,本文提出了基于斯坦福永久散射体干涉算法(STanford Method for Persistent Scatterers, StaMPS)的星地双基地时序InSAR全链路信号处理方法,该方法针对星地双基地SAR非合作成像特点,采用基于局部干涉相位条纹精估计的方法补偿重轨干涉误差,并针对星地双基地SAR接收端高度低导致目标区域存在遮挡效应的问题,利用等效视线投影法判别可视区域。进一步,针对重轨观测图像幅度差异大的问题,基于均匀稳定区域的像素实现星地双基地SAR图像的幅度校正。最后,采用双阈值法进行永久散射体(Persistent Scatterer, PS)点筛选,并基于StaMPS实现星地双基地时序InSAR处理。本文通过仿真验证了所提模型和方法的有效性,并基于陆探一号(Lutan-1, LT-1)首次开展了星地双基地时序InSAR面场景实验。通过28幅济南市实验区域LT-1重轨星地双基地SAR图像的双基地时序InSAR处理,获得了面场景形变速率。与Sentinel-1A单星数据时序InSAR处理结果的交叉对比表明,基于LT-1的星地双基地时序InSAR实测处理精度为5.424mm/yr,验证了本文所提模型与方法的有效性。

     

    Abstract: ‍ ‍The space-surface bistatic synthetic aperture radar (SAR) utilizes a ground-based receiving system to passively receive spaceborne SAR signals, and has the advantage of flexible receiving geometry. The high-precision deformation rate of the scene can be inverted by time-series interferometric SAR (InSAR) processing, which has potential applications in the high-frequency investigation of geological disaster areas. However, there is no relevant research on space-surface bistatic time-series InSAR. A space-surface bistatic time-series InSAR measurement model is first established according to the geometric characteristics of space-surface bistatic SAR observation. Then, a full-link signal processing method for space-surface bistatic time-series InSAR based on the STanford Method for Persistent Scatterers (StaMPS) is proposed. To compensate for the repeat-pass interferometric phase error due to the noncooperative imaging of space-surface bistatic SAR, a method based on fine estimation of local interferometric phase fringe is used. To deal with the occlusion effect in the target area caused by the low height of the receiving system of the space-surface bistatic SAR, the equivalent line-of-sight projection method is used to distinguish the visible area. To solve the problem of the large amplitude variation of repeat-pass SAR images, an amplitude correction method is adopted using the pixels in the uniform and stable region. Finally, the double-threshold method is used to screen the persistent scatterer points, and the space-surface bistatic time-series InSAR processing is realized based on StaMPS. The effectiveness of the proposed model and method is first verified by simulation. Then, the area scene experiment of space-surface bistatic time-series InSAR is carried out for the first time based on Lutan-1 (LT-1). Using 28 LT-1 repeat-pass space-surface bistatic SAR images of the Jinan experimental area, an area scene deformation rate is retrieved by time-series InSAR processing. The cross-comparison of the results of InSAR processing with Sentinel-1A monostatic SAR data shows that, the processing accuracy of the space-surface bistatic time series InSAR based on LT-1 is 5.424 mm/y, verifying the effectiveness of the model and method proposed in this paper.

     

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