【作者】 张永俊；

【导师】 梁甸农；

【作者基本信息】 国防科学技术大学 ， 信息与通信工程， 2011， 博士

【摘要】 星载分布式干涉合成孔径雷达(InSAR)系统是近年来兴起的一种新体制雷达系统,它把卫星编队技术和星载SAR技术紧密结合在一起,通过多颗卫星编队飞行、协同工作来进行地形高程测量。相对于其它地形高程测量手段和传统InSAR系统,星载分布式InSAR系统具有测高精度高、生存和抗干扰能力强、周期短、成本低等优势,是目前国内外研究的热点,尤其是第一个星载分布式InSAR系统-德国TanDEM-X系统的成功在轨运行,更是将这一新体制雷达系统的研究推向高潮。本文瞄准这一前沿课题,系统地研究了星载分布式InSAR系统的测高原理、全链路误差模型和DEM精度提高方法。其中,第二章和第三章主要是误差的传播和误差的建模及影响分析,第四章和第五章是DEM精度提高方法研究。各章具体内容安排如下:第二章研究了星载分布式InSAR系统与传统InSAR系统测高原理的异同点,并证明了其测高误差敏感度之间的近似等价性。从新系统三维定位原理出发,系统地分析了其误差敏感度,并与传统InSAR系统测高原理及其误差敏感度进行了对比分析,证明了新系统与传统InSAR系统测高误差敏感度的近似等效性,给出了近似条件。第三章研究了星载分布式InSAR系统的综合误差模型。根据新系统的三维定位原理,引出系统的一级误差源,对各误差源的误差特性进行了深入分析,以此为基础得到系统的全链路误差模型和综合误差模型,基于全数字仿真系统对误差模型进行了仿真验证;研究了系统的关键误差-干涉基线误差和波束同步误差对系统性能的影响规律,并利用全数字信号仿真系统进行了仿真验证。第四章研究了星载分布式InSAR系统DEM产品的校正问题。首先讨论了经典干涉定标方法定标精度较低的原因,提出四种改善定标精度的策略,在此基础上提出一种干涉定标优化方法,给出了地面定标器的布放规则;分析了目前常用的三种基于地面控制点的DEM校正方法的优缺点,提出一种基于星载分布式InSAR系统综合误差模型的DEM校正方法,该方法利用误差模型的约束,可有效消除系统误差的影响,同时抑制控制点误差的传播;针对全球无缝拼接高精度DEM的迫切需求,研究了基于多幅相邻DEM交叠区域的系统误差联合校正方法,该方法可同时对多幅DEM进行校正,得到无缝拼接的大场景DEM数据,同时,可以对没有控制点支撑的DEM进行校正。第五章研究了星载分布式InSAR系统干涉基线和波束同步方案的优化设计方法。为了减小各干涉参数误差的影响,分析了传统最优基线概念的不足之处,全面地研究了干涉参数误差、垂直有效基线长度、沿航迹基线长度和测高精度、系统总相干系数及信号处理难度之间的关系,提出了一种干涉基线优化设计的工程化方法,在保证干涉处理顺利进行的同时降低了干涉参数误差的误差传递系数,提升了DEM产品的精度;针对单星多普勒中心频率估计误差,提出了基于椭圆轨道的全零多普勒方法,并在此基础上提出一种适用于椭圆轨道的偏航导引方法,这两种方法可以通过对卫星姿态的调整使得雷达回波多普勒中心频率为零,前者同时利用偏航导引和俯仰导引,后者仅利用偏航导引达到相同效果,有效地消除了多普勒中心频率过大及其估计误差对单站SAR成像的影响;针对波束同步误差,提出一种最大相干波束同步方法,相对于传统波束同步方法,该方法对双星分别进行导引,降低了卫星姿态、波束指向工程实现的协同难度,可有效提高系统相干系数和多视处理时的独立视数,消除干涉时刻配准误差带来的影响,同时由于单双站多普勒中心频率同时为零,可以提高信号处理的效率,最终提升DEM精度。更多还原

【Abstract】 Spaceborne distributed interferometric synthetic aperture radar (InSAR) is a novel remote sensing system, which is an integration of the the spaceborne SAR and satellite formation flying technology. The system fulfills the three-dimensional terrain mapping by formation flying and cooperation of several satellites. Because of its advantages such as high vertical accuracy, strong survival capability and antijamming ability, short scanning cycle and low cost, the novel InSAR system has been one of the research hotspot around the world, especially the successful launch of the first spaceborne distributed InSAR system– TanDEM-X, makes the new system a new upsurge. Aiming at the novel system, the three-dimensional localization principles, the total error model, the DEM precision improvement methods are studied systematically. Here the chapter 2 and chapter 3 analyze the transference and the influence of parameter error, the chapter 4 and chapter 5 analyzes the DEM precision improvement methods. The work demonstrated in this thesis is expected to support the realization of future InSAR system. The research in each chapter is arranged as following:The three-dimensional localization and altimetry principles and the error sensitivity of the spaceborne distributed InSAR system are studied in chapter 2. The localization and altimetry principles of the new system are compared with the height measurement principles of two traditional InSAR systems as well as the error sensitivity. The equivalence among three model’s error sensitivity is also proved in this chapter.The error problem of the spaceborne distributed InSAR system is studied in chapter 3. Based on the three-dimensional localization equations, the first order error sources of the new system are derived, and the property of every single error is analyzed in detail, then the total error model of the new system is set up. Computer simulation experiment is carried out to demonstrate the validity of the total error model. Key error of the new system are discussed here, the influences introduced by the interferometric baseline error and the illumination synchronization error are analyzed theoretically and demonstrated by computer simulation.Chapter 4 focuses on the calibration problems of the new system’s DEM product. Firstly, the reasons that conventional parameter calibration algorithms for InSAR system has a low accuracy are analyzed, four ways which can improve the calibration accuracy is presented, then an optimized parameter calibration algorithm is proposed, and the basic principles of disposing calibrators are given. Secondly, three typical DEM calibration algorithms based on the ground control points (GCPs) are analyzed, a new DEM calibration algorithm based on the total error model is brought forward, because of the using of the total error model, the algorithm can eliminate the systematic error and suppress the height error of GCPs efficiently. Finally, considering the urgently requirement of the high accuracy global mosaic DEM, a joint calibration method which uses the superposed areas of the adjacent DEMs information is proposed to calibrate several DEMs simultaneously, its product is a mosaic DEM of the whole big scene. The method can calibrate the DEM of scene which has no GCPs, the computer simulation results demonstrate the availability of the method.The optimization design of the system is studied in chapter 5. To minimize the influences of the interferometric parameters error, the limitation of the conventional concept of the optimal baseline is analyzed, and the relationships between the interferometric parameters error and the vertical accuracy, the perpendicular effective baseline and the vertical accuracy as well as the difficulty of the signal processing, the along track baseline and the total coherence are studied, then a interferometric baseline optimization method is proposed. Focusing on the estimation error of the doppler centriod, an elliptic orbit total zero doppler steering method is proposed, furthermore a novel yaw steering method is proposed, those two methods can decrease the doppler centroid to zero by adjusting the attitude of the satellite, the former must adjust the yaw and the pitch attitude at one time, while the latter only need adjusting the yaw attitude, the two methods can restrain the estimation error of the doppler centriod by reducing the doppler centriod to zero. Focusing on the illumination synchronization error, based on the two methods presented ahead, a maximum coherence illumination synchronization method is proposed. Compared with the traditional method, the new method steers the two satellites respectively and decreas the difficulty of attitude and beam-steering cooperation between the two satellites. The new method can enhance the coherence and the number of the independent looks for interferometric phase estimation, and eliminate the influences introduced by the error of interferometric coregistration time and improve the processing efficiency. Because of the zero doppler centroid, at last, the new method can upgrade the DEM precision.更多还原