星载SAR图像方位角计算及其对风速反演影响评估  

Calculation of Spaceborne SAR Image Heading and Its Impact on Wind Speed Retrieval

作　　者：李慧敏 胡登辉 林文明 王臣 何宜军 LI Huimin;HU Denghui;LIN Wenming;WANG Chen;HE Yijun(School of Marine Sciences,Nanjing University of Information Science and Technology,Nanjing 210044;Key Laboratory of Space Ocean Remote Sensing and Application,Ministry of Natural Resources,Beijing 100081;Innovation Academy for Microsatellites,Chinese Academy of Sciences,Shanghai 201203)

机构地区：[1]南京信息工程大学海洋科学学院,南京210044 [2]自然资源部空间海洋遥感与应用重点实验室,北京100081 [3]中国科学院微小卫星创新研究院,上海201203

出　　处：《空间科学学报》2023年第6期1081-1090,共10页Chinese Journal of Space Science

基　　金：国家自然科学基金项目(43006163,42206179,42027805);江苏省基础研究项目(BK20210666);国家重点研发计划项目(2021YFC280330)共同资助。

摘　　要：星载合成孔径雷达(Synthetic Aperture Radar, SAR)是海洋常规观测的重要技术手段,然而在其数据处理和关键物理参数反演中,SAR图像方位角SAR海面风速的反演精度。对此,根据SAR图像方位角的定义,结合空间卫星坐标系转换关系推导了?IMG,并进一步提出了基于SAR图像地面控制点的?IMG计算方法。通过对比分析2016年全球近70万景哨兵一号卫星波模式SAR图像,量化了?IMG与?SAT的系统偏差,发现该偏差与雷达入射角和轨道方向紧密相关。选用五次多项式拟合该偏差随纬度的变化规律,同时发现将卫星飞行方向角近似等于SAR图像方位角会引起海面风场反演误差,该误差空间分布不均,且升轨降轨有所差异,风速误差最大可达±0.5 m·s–1。研究结果表明,?IMG的正确计算和使用对于SAR地球科学研究具有重要意义,本文提出的?IMG计算方法对其他SAR卫星系列也具有实际参考价值。The spaceborne Synthetic Aperture Radar(SAR)is a broadly acknowledged technique to monitor the vast open ocean.However,a frequent confusion between the SAR image azimuth angle and the satellite flight direction exists in the data processing and geophysical applications,which influences for instance the accuracy of SAR wind inversions.An overview of derivation from the transformation of the spatial satellite coordinate systems is presented in this paper,along with a method for calculating based on the Ground Control Points(GCP).By analyzing a set of 0.7 million Sen-tinel-1 SAR wave mode images acquired in 2016,we quantify the systematic bias between φdng and φSAT and find out that this bias is related to the incidence angle and orbital direction.It can be accurately fit-ted using a fifth-order polynomial relative to latitude.The misuse of φSAT is demonstrated to approxi-mate can lead to nonnegligible wind retrieval errors.The spatial distribution of this wind error is non-uniform and differs between ascending and descending orbits,with a wind speed bias of±0.5 m·s^(–1).Results obtained in this study evidence that the precise estimate of are significant to various SAR applications in relevant studies.The proposed method here also holds practical reference for other satel-lite SAR missions.

关 键 词：合成孔径雷达 图像方位角 风场反演精度 哨兵一号卫星 

分 类 号：P236[天文地球—摄影测量与遥感]