轨道不平度对天线指向的影响分析与修正

摘要

基于天线轨道不平度对望远镜指向的影响机理,测量并分析采用整体焊接轨道技术后的乌鲁木齐南山26 m射电望远镜(NanShan Radio Telescope,NSRT)天线轨道误差的分布情况及对指向的影响,从而对指向模型进行修正.采用移动最小二乘法(Moving Least-Squares,MLS)将测得的天线轨道高度差拟合成一个闭合的轨道高度分布曲线,确定因轨道不平度影响的天线方位轴偏差,对比实测天线座架变形的方位轴偏差,发现二者具有较强的相关性.考虑到天线座架重力变形的偏差包含南北向和东西向偏差,建立新的指向偏差模型进行校正.最后通过对已知校准射电源进行扫描测量,将指向偏差数据进行拟合.结果表明:新建的指向修正模型能够抑制已知指向模型偏差中的正弦分量,从而说明所建模型很好地反映了天线的指向偏差并对偏差具有一定修正作用.%According to the influence mechanism of the antenna track irregularity on telescope pointing accuracy,the distribution of the track deviation and the influence of the deviation on the pointing of the Urumqi Nanshan 26 m telescope are reanalyzed,and provided that the whole welding track technology is used,thus the pointing model is correspondingly corrected.By using the moving least-squares method to fit the height of antenna track as a closed curve,the antenna azimuth tilt can be determined through the track irregularity.Through comparing the measured deviation of the antenna azimuth axis which is introduced by the deformation of the antenna mount frame,it can be found that the measured deformation is strongly correlated with the theoretical deformation.A new pointing model of deviation is established in view of the gravity deformations of antenna including the north-south and east-west deviations.Furthermore,the data of pointing deviation are filtered through scanning a known calibration radio source in the sky.The result shows that the sinusoidal component of the model deviation is well constrained by the new pointing correction model,thus it demonstrates that the new model can well reflect the antenna pointing deviation as well as amend it in some extend.