子镜面内位移对中国巨型太阳望远镜主镜控制的影响

Effects of In-Plane Displacement on Primary Mirror Control of Chinese Giant Solar Telescope

针对中国巨型太阳望远镜(CGST)的8m环形太阳望远镜(8m-RST)设计方案,建立了其边缘传感器和光学传感器响应子镜面内位移量的模型,进而分析了子镜面内位移对环形拼接主镜面形保持的影响。考虑了望远镜桁架因望远镜指向和温度改变所引起的子镜面内位移量,发现该位移量会破坏8m-RST的面形保持效果。为解决面内位移对8m-RST面形保持的不利影响,提出了相应的主镜控制模型改进方案。改进方案是:通过在子镜拼缝处加装两组间隙量传感器和一组剪切量传感器,利用增加的探测量估算子镜的面内位移量,进而修正边缘传感器与光学传感器的设定值。当间隙量和剪切量的探测精度优于23nm时,改进方案可以满足CGST的8m-RST方案的面形保持要求。

Against the design scheme of 8 m ring solar telescope （8m-.RST） of Chinese Giant Solar Telescope （CGST）, the model of the edge sensor and optical sensor response in segments displacement is established, and the influence of the segments in-plane displacement on the surface shape of ring segmented primary mirror is analyzed. Considering the segmentsI displacement introduced by zenith angle change and temperature change for telescope truss, it＇s found that the displacement will destroy the effect of surface shape keeping of 8m-RST. To avoid the adverse effect of the in-plane displacement on 8m-RSTI an improvement plan of the corresponding control model for the primary mirror is proposed. Which is correcting the set value of the edge sensor reading and the optical sensor reading, by adding two groups of gap sensor and one group of shear sensor among the edge of neighbor segments and using increased detection amount to estimate the in-plane displacement. When the detection accuracy of the gap and shear is less than 23 nm, the improved plan can meet the surface shape requirement of 8m-RST scheme for CGST.