星载激光光斑影像激光指向变化探测法

Laser pointing changes detection method for space-borne laser spot image

地面光斑足印的定位精度高度依赖于激光指向角的测量精度,星载激光光斑质心提取及其变化规律对激光指向角的分析具有重要的意义。本文基于ICESat/GLAS的激光剖面阵列(laser profile array,LPA)影像数据,首先利用灰度一阶矩阵法提取LPA的质心,精度优于0.3个像素,LPA相对定位精度优于0.11个像素。其次利用傅里叶变换和傅里叶级数拟合对LPA质心坐标的变化进行周期探测和建模分析,结果表明,激光光斑影像的质心坐标存在1.83×10^-4 Hz、3.36×10^-4 Hz、5.19×10^-4 Hz和6.71×10^-4 Hz 4个明显的周期变化,拟合结果的相关性R2达到了0.86,拟合精度可达0.4″,优于0.13个像素,得到了较好的结果。可为我国的高分七号和后续的卫星激光测高数据处理提供参考。

The positioning accuracy of the ground spot footprints is highly dependent on the positioning accuracy of the laser pointing angle.The centroid extraction and its variation law of space-borne laser spot are of important significance to the analysis of laser pointing angle.Firstly,based on the laser profile array(LPA)image data of ICESat/GLAS,this paper uses the gray-scale first-order matrix method to extract the centroid of LPA,with an accuracy better than 0.3 pixels,and the relative positioning accuracy of LPA is better than 0.11 pixels.next,Fourier transform and Fourier series fitting are used for periodic detection and modeling analysis of LPA centroid coordinates changes.The results show that the centroid coordinates of the laser spot image have four obvious periodic changes:1.83×10^-4 Hz,3.36×10^-4 Hz,5.19×10^-4 Hz and 6.71×10^-4 Hz.The correlation R2 of fitting results reached 0.86,and the fitting accuracy was up to 0.4″,which was better than 0.13 pixels,and a better result was obtained.It can provide reference for the data processing of GF-7 and the subsequent satellite laser altimeter.