Abstract
Gaofen-3 (GF-3) is China’ first C-band multi-polarization synthetic aperture radar (SAR) satellite, which also provides the sliding spotlight mode for the first time. Sliding-spotlight mode is a novel mode to realize imaging with not only high resolution, but also wide swath. Several key technologies for sliding spotlight mode in spaceborne SAR with high resolution are investigated in this paper, mainly including the imaging parameters, the methods of velocity estimation and ambiguity elimination, and the imaging algorithms. Based on the chosen Convolution BackProjection (CBP) and PFA (Polar Format Algorithm) imaging algorithms, a fast implementation method of CBP and a modified PFA method suitable for sliding spotlight mode are proposed, and the processing flows are derived in detail. Finally, the algorithms are validated by simulations and measured data.
Highlights
Gaofen-3 (GF-3), launched on 10 August 2016, is China’s first C-band multi-polarization synthetic aperture radar (SAR) satellite, mainly used in the fields of ocean surveillance, land observation, disaster reduction, and water conservation [1]
Stripmap mode can provide images of large areas continuously, but the azimuth resolution cannot be arbitrarily increased; spotlight mode is achieved by controlling the scanning speed of the antenna so that it can fix on a certain ground area to improve the coherent integration time (CPI), so the azimuth resolution can be higher, but the imaging range is limited by the antenna beam width
The mechanism of the Convolution BackProjection (CBP) algorithm and Polar Format Algorithm (PFA) algorithm for SAR imaging are studied, and the process of the fast application in spaceborne sliding spotlight SAR is analyzed in detail
Summary
Gaofen-3 (GF-3), launched on 10 August 2016, is China’s first C-band multi-polarization synthetic aperture radar (SAR) satellite, mainly used in the fields of ocean surveillance, land observation, disaster reduction, and water conservation [1]. Stripmap mode can provide images of large areas continuously, but the azimuth resolution cannot be arbitrarily increased; spotlight mode is achieved by controlling the scanning speed of the antenna so that it can fix on a certain ground area to improve the coherent integration time (CPI), so the azimuth resolution can be higher, but the imaging range is limited by the antenna beam width. The fast realization method of CBP based on Quadtree recursive sub-image segmentation is studied, which is realized by sub-image interception, fast filtering and down-sampling to reduce the computation. In this paper, based on the CBP algorithm of Quadtree recursive sub-image segmentation, it is further extended to the PFA algorithm, which greatly improves the effective imaging scene size of PFA. The proposed algorithms are verified by simulation and measured data
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