大气湍流对环形拼接望远镜主动控制中光学倾斜测量的影响

Effect of Atmospheric Turbulence on Optical Tip Measurement of Active Control of Ring Segmented Telescope

从理论上分析了大气湍流引起的球面波波前到达角的时空统计特性。讨论了在近地湍流环境中,利用光学倾斜测量方法实现高精度、高带宽的拼接望远镜主动对准的可能性。在研究到达角的空间相关性时考虑了有限湍流外尺度效应。同时,为研究时间相关性,计算了到达角的时间互谱密度。通过数值计算得到了单次短曝光测量误差的均方值以及时间积分抑制误差的效应。给出了在不同湍流环境和0.01″测量精度要求下的倾斜控制带宽。

Theoretical investigations of the spatio-temporal statistical properties of arrival angle of a spherical wavefront perturbed by atmospheric turbulence are presented. The motivation is to evaluate the practicality of a high accuracy and high bandwidth active alignment for a ring segmented telescope used an optical tip measurement. The effect of finite wavefront outer scale is considered for exploring the spatial coherence of arrival angle. The temporal cross-spectrum of arrival angle is also calculated for studying the temporal coherence. The mean square of measurement error for a single short-exposure is calculated numerically. While, the magnitude of suppressing the error by time integration is discussed. The control bandwidth is calculated for an accuracy requirement of 0.01″ in some different cases of turbulence environment.