时空变背景电离层对GEO TomoSAR成像影响分析

Impacts of Temporal-Spatial Variant Background Ionosphere on Geosynchronous SAR Tomography

地球同步轨道合成孔径雷达层析成像(GEOTomoSAR)是一种将地球同步轨道SAR(GEOSAR)与三维层析成像相结合的技术,它能够克服低轨SAR层析成像中重访时间长、时间去相干严重等缺点,实现对地面场景及时、精确地三维重建。但是由于GEOSAR轨道高,信号能够穿过整个电离层,使得GEOSAR信号时延长,引入严重的相位误差,进而影响GEOTomoSAR三维成像的精度。本文主要从背景电离层对雷达信号传播的影响机理出发,建立了时空变背景电离层影响下的GEOTomoSAR信号模型,进而分析了对三维成像的影响。经过分析,时空变背景电离层对GEOTomoSAR系统的影响主要包括成像目标的相对位置偏移以及高度向成像散焦。最后,通过计算机仿真验证了理论分析的正确性。

Geosynchronous SAR tomography (GEO TomoSAR) is a technique that combines geosynchronous SAR (GEO SAR) with SAR tomography. It can overcome the shortcomings of long revisit time and serious decorrelation in low Earth orbit SAR tomography, and realize timely and accurate three-dimensional reconstruction of targets. However, due to the high orbit of GEO SAR, the signal can pass through the entire ionosphere, causing the signal to have a long time delay. Signal delay introduces the error phase, which in turn affects the accuracy of GEO TomoSAR 3D imaging. In this paper, based on the influence mechanism of background ionosphere on radar signals, the GEO TomoSAR signal model under the influence of temporal-spatial variant background ionosphere is established, and its influence on three-dimensional imaging is analyzed. After analysis, the influence of the background ionosphere on the GEO TomoSAR system mainly includes the relative offset of the scattering target and the imaging defocus in the elevation direction. Finally, the correctness of theoretical analysis is verified by computer simulation.