近天底干涉SAR动态海面高程测量误差分析

采用近天底的宽刈幅干涉高度计是近年来新发展的海面高程测量技术，与陆地高程测量不同，海浪一直处于随机运动之中，其动态特性会在合成孔径雷达(SAR)成像和干涉处理中引入显著误差。对于厘米级的干涉测量精度要求来说，该误差是主要误差源之一。该文研究了由海面特性引起的高程误差机理及其对于近天底干涉SAR测高精度的影响，建立了运动误差理论模型，同时考虑了电磁偏差与叠掩偏差影响。基于不同SAR工作体制，在不同海况下进行了理论近似仿真，并进行了干涉SAR全链路仿真，全链路仿真结果能够与理论仿真较好地吻合，验证了误差模型的正确。结果显示由海浪引起的误差随着多普勒中心频率近似呈线性变化，且与目标散射加权径向速度成正比。误差不仅与海浪特性相关，还与雷达系统参数相关，这能为未来系统设计、误差预算和海面高程处理提供参考。

Error Analysis of Dynamic Sea Surface Height Measurement by Near-nadir Interferometric SAR

The wide-swath interferometric altimeter working at near-nadir is a newly developed ocean surface topography measurement technology in recent years. Different from land elevation measurement, for the dynamic ocean surface waves, they move randomly all the time and this brings bias in Synthetic Aperture Radar (SAR) imaging and interferometric processes and leads to the final height measurement errors. For the requirement of centimeter-level precision, this error is the main source of measurement errors. The errors due to the characteristics of ocean surface and their impact on near-nadir InSAR’s precision are investigated. The motion error theoretical model is established combining the characteristics of the ocean surface and InSAR working mechanism, and the electromagnetic bias and layover bias are also taken into consideration. The error models in different SAR modes under various sea states are simulated. The error model is validated by the interferometric SAR full-link experimental simulation and the simulation results are consistent with the theoretical values. The results show that the errors are approximately linear changing with the Doppler centroid frequency and are proportional to the radial velocity of targets modulated by scattering. The errors are not only related to the characteristics of the waves, but also related to system parameters. This work can provide the feasible suggestions for future system design, error budget and data processing.