Spaceborne SAR Terrain Matching Curved Imaging Method and Satellite Demonstration: (I) Curved Geometric Configuration

The spaceborne synthetic aperture radar (SAR) terrain matching curved imaging is a mode proposed for efficiently imaging the long curved terrains, e.g., coastlines and river banks in a high resolution. The key feature is the employment of a curved imaging swath matched with the orientations of the long curved terrains. However, due to the complexity of long curved terrain, the target illumination time has a violent variation, tending to cause a large fluctuation of azimuth resolution within a single imaging. In this article, a new geometric configuration optimization method is proposed to achieve the uniform azimuth resolution by elaborately controlling the beam in a complex nonlinear way while tracking the terrain orientation. The main technical contributions are twofold: first, a predict-grow beam control model is built to continuously adjust the target illumination time thereby mitigating the azimuth resolution fluctuation. Second, a stepwise solving method is proposed to obtain the specific beam pointing sequence along the long curved terrain satisfying the physical restrictions of beam steering. The effectiveness of the presented approaches is verified via the computer simulations and the real data experiment conducted by the SmartSat-X1 satellite.