不同TEC分布模式对星载SAR立体定位精度的影响及校正

Influence of Different Distribution Patterns Ionosphere on Space-Borne SAR Stereo Positioning Accuracy and Correction

基于SAR成像模型和R-D定位模型,分析了电离层对星载SAR立体定位精度的影响,提出了相应的校正方法,并进行了仿真实验。实验表明对于特定波长的SAR信号,不同TEC分布模式组合对SAR立体像对定位精度的影响不同,校正效果也不同:当两幅影像对应的TEC分布均匀且大小相同时,电离层对SAR立体定位精度的影响小到可以忽略;当两幅影像由于拍摄季节不同导致TEC不同时,电离层影响很大,特别是距离向精度,其影响程度与两幅影像对应的TEC差值正相关,此时定向参数精化法校正效果很好;当电离层发生扰动时,电离层影响随着扰动程度的增大而增大,定向参数精化法有一定效果,但当电离层扰动很大时,校正效果明显减弱,还需要通过斜距直接校正法等其他方法予以校正。

Based on SAR imaging model and R-D positioning model, the effect model of ionosphere on space-borne SAR positioning precision was constructed, and the corresponding correction methods were proposed. Simulation experiment was carried out to analyze the degree of influence and verify the correction effect. The experimental re- suits show that for a particular wavelength of the SAR signal, the impact of the different distribution patterns of TEC on positioning accuracy and correction effect are different： when the TEC distribution of two images are uni- form and have same value, the impact on SAR stereo positioning accuracy is so little that it can be ignored; when the ionosphere is in a calm state and the TEC values of the two images arenot the same due to the different sea- sons, the influence is great, especially on distance accuracy, and the affects can be well compensated through ori- entation parameters refinement; for the uneven distribution of TEC, the impact is greater as ionosphere disturbance degree increases, and it can＇t be eliminated well through the orientation parameter refinement when ionospheric disturbances is serious, so it must be corrected by direct slant range correction or other methods.