等效斜视距离模型在星载LEO-SAR中的精度分析

Analysis of Effective Slant Range Model Accuracy Based on Low-Earth-Orbital(LEO) Spaceborne SAR

该文旨在研究等效斜视距离模型在低轨星载SAR高分辨率情况下的适用性,并分析其最佳性能——即该模型适用的最长合成孔径时间及对应的最高分辨率。该文首先通过建立精确的"星-地"几何模型推导出具有较高精度的多普勒中心和多普勒调频率计算公式,进而通过多普勒参数反演得到等效斜视距离模型。通过与数值方法得到的斜距信息比较,可以得到该距离模型拟合结果的误差,当该误差在p/4阈值之内,图像就不会散焦。利用该思想,该文以TerraSAR-X参数为例,分析了等效斜视模型可以适用的最长合成孔径时间及对应的最高分辨率。该文结论给一般的低轨星载SAR距离模型分析提供了一种普适的方法。

This paper aims at analyzing the applicability of the hyperbolic range model meeting resolution higher than one meter for low-earth orbital spaceborne SAR. How long the integration time can the range model be applied to, and the corresponding azimuth resolution are main issues of this paper. An accurate geometry is modeled firstly to get the Doppler centroid and the Doppler FM rate, which have the higher accuracy. Then the accurate range model can be got through the Doppler parameter reversion. The azimuth history phase errors can then be calculated by comparing with the numeric values of the slant range information. If the errors are under the threhold of 7r/4, the disfocusing is impossible. Based on the theory above, the parameters of TerraSAR-X are utilized for simulation. The longest integration time and the best resolution got from the hyperbolic range model are analyzed. The conclusion of this paper offers an approach for analyzing the range model of the current low-earth orbital spaceborne SAR.