空间相机地心距误差修正

为了修正时间延迟积分(TDI) CCD空间相机像移补偿计算中的地心距误差,减小其对像移速度相对误差的影响,推导出了星下点成像的像移速度计算模型.通过该模型分析了地心距误差对像移速度相对误差的影响.根据地心距误差的来源,分两步修正了地心距误差:采用WGS-84(World Geodetic System)模型修正地球的偏心率引起的地心距误差；采用地球海拔高度数据源(USGS DEM)制作电子高程图,修正了地球表面海拔高度不同引起的地心距误差.推导出了地心距误差修正后的空间相机星下点成像的像移速度模型.修正后模型计算以及分析结果表明:WGS-84模型和电子高程图对地心距误差的修正消除像移速度相对误差最大分别为2.85％和1.76％.地心距误差的修正极大地减小了前向(沿TDI CCD积分方向的)匹配误差,提高了TDI CCD空间相机成像质量.

Modification of geocentric distance error of space camera

To modify the geocentric core distance error of a Time Delay and Integration(TDI) CCD space camera in the calculation of image motion compensation,and decrease the influence of the error on the match error of image motion velocity,a model of image motion calculation of points bellow satellites was deduced.The influence of the geocentric core distance error on the relative error of image motion velocity was analyzed based on the model,and the geocentric core distance error was modified by two steps according to the error sources.The former adopted the World Geodetic System(WGS-84) to modify the error generated by ellipticity of the error,and the latter used the data source of the earth’s height above sea level(United States Geological Survey Digital Elevation Model,USGS DEM) to make a digital elevation map modify the error generated by the deference heights above sea level.After modifying,the image motion model of points bellow satellites was deduced.The calculation and analysis by the model indicate that the maximum error of image motion velocity eliminated are about 2.85% and 1.76% with the modification of geocentric core distance error by the WGS-84 model and digital elevation map,respectively.Those data clearly show that the match error of forward direction(the integral direction of TDI CCD)has been greatly decreased by modifying the geocentric core distance error,and the imaging quality of TDI CCD space camera has improved greatly.