夏克-哈特曼波前传感器双星波前误差测量计算大气非等晕误差的研究

Research on Double Star Wavefront Error Detection with Shack-Hartmann Wavefront Sensor to Calculate Piston-Removed Anisoplanatic Error

等晕误差中的piston项对成像质量没有影响,无需校正,有效非等晕误差应去除该项。为此提出利用夏克哈特曼波前传感器测量双星波前误差的方法,计算得到去piston项误差后的等晕角。首先,根据Sasiela和Van Dam给出的角度非等晕误差解析表达式,计算不同条件下的非等晕误差理论值;其次,利用相位屏法,模拟不同大气环境下实际自适应光学系统波前误差测量过程,仿真得到非等晕误差值。数值仿真结果与理论计算有较好的吻合,并得到了波前误差与去piston项等晕角的对应关系。最后,基于丽江1.8 m望远镜系统,测量双星的非等晕误差,计算得到去piston项等晕角的大小。并使用差分像运动法和恒星闪烁法,对该方法进行了印证。去piston项等晕角测量实验的结果表明,去piston项等晕角在时间维度上变化缓慢,在空间维度上差别很大,当方位及仰角差距较远的情况下,去piston项等晕角的值没有相关性。根据该方法,也可计算出其他望远镜及大气模型下的波前误差值与去piston项等晕角的对应关系,为信标的位置选择提供了依据。

Piston aberration in isoplanatic error does not affect imaging quality and requires no calibration;therefore,effective anisoplanatic error should eliminate piston aberration.The approach to compute the pistonremoved isoplanatic angle is proposed in this study,which involves measuring double star wavefront error with ShackHartmann wavefront sensor.First,the value of the anisoplanatic error in various atmospheric environments is computed using Sasiela and Van Dam analytical expression for angle anisoplanatic error.Thereafter,the process of wavefront error measurement in an actual adaptive optics system with different atmospheric conditions is simulated and the anisoplanatic error is computed using phase screen method.The numerical simulation findings and theoretical calculations are similar.Meanwhile,the correspondence between wavefront error and pistonremoved isoplanatic angle is computed.Finally,the anisoplanatic error of double stars is estimated and the pistonremoved value of the isoplanatic angle is computed in Lijing 1.8-m astronomical telescope.The finding is confirmed using the approaches of differential image motion and stellar scintillation.The experimental findings exhibit that the pistonremoved isoplanatic angle differs slowly in the temporal dimension and rapidly in the spatial dimension,and the importance of the pistonremoved isoplanatic angle will be lost with long distance.Based on the approach,the correspondence between wavefront error and pistonremoved isoplanatic angle in other atmospheric models and telescopes could be computed and it offers a basis for the location of the beacon.