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

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.