星载合成孔径雷达构像方程是地理编码、立体测量、影像定位等几何处理的基础。本文首先讨论了构像方程的参数选择,在充分考虑轨道物理模型及摄动力影响的基础上,提出了一套改进的轨道模型参数。从距离方程及多普勒方程出发,详细推导了包含轨道模型参数及成像处理参数的星载SAR构像方程。作为构像方程的一个具体应用,本文研究了星载SAR影像的轨道精化问题。将构像方程线性化,对每个地面控制点列出误差方程,可以用类似于航空影像的空间后方交会的方式精确求解轨道模型参数。试验中从1∶5万地形图上量取了5个地面控制点,对一景Radarsat SAR影像进行了轨道精化。比较发现,头文件提供的轨道与精化的轨道之间有约2km的位置差异,用精化的轨道数据得到了高精度的几何校正结果。它间接地表明了轨道精化算法的正确可行。

Imagingmodel is the basis formost geometric processing of space-borne SAR mi agery, including miage rectification, radargrammetry and mi age geolocation. This paperdevelops a parametric mi agingmodel for SAR, which explicitly describes the relationship between the 3D cartographic coordinate ofa ground targetand the 2D mi age coordinate of the corresponding pixe.l The parameters of mi agingmodel consist of near range,mi age starting tmie,Doppler parameters and orbit parameters. After quantitatively evaluating the influence of the Earth perturbations on satellite orbit, we present an mi proved satellite orbit mode,l which uses less parameters and is able to fit the space orbit atnearly the same accuracy comparedwith classicalmode.l As an application of the mi aging mode,l an orbit refinement algorithm using ground control points(GCPs) is presented. For this purpose, the mi agingmodel is rewritten to incorporate only 9 orbit parameters, and then\nlinearized through differentiatingwith respect to the orbitparameters. For eachGCP, the mi age coordinates are expressed as the function of the orbitparameters and two error equations are formed. The orbitparameters can\nthen be iteratively determined through solving a linear equation set consisting of the error equations from all GCPs under least square rule. The orbit refinement algorithm is tested on a RADARSAT SGF ( SAR Georeferenced Fine resolution product) scene. 5 GCPs are identified from 1∶50000 scale topographicmaps to refine the orbit parameters coming with the SGF mi age. The accuracy of the refined orbit is demonstrated through geometric correction of the SGF mi age. While the SGF data is poorly corrected using the original orbit\ndata, it is precisely correctedwith refined orbitparameters.