Recently, Yunnan Observatories has made important progress in active optical technology for large-aperture solar telescopes. Segmented primary mirror active optical technology is the main development direction of ground-based astronomical telescopes. For astronomical telescopes larger than 8 meters in diameter, the segmented primary mirror solution is usually adopted. The 8-meter annular segmented primary mirror is one of the key solutions for the China Giant Solar Telescope (CGST). Compared with the whole mirror solution, it can significantly reduce development costs and risks. CGST plans to make high spatial resolution observations of the solar atmosphere in the visible and near-infrared bands, so it requires the realization of co-phase in the visible and near-infrared bands. Due to the complex operating environment of solar telescopes, traditional electromechanical edge sensors will be affected by the complex observing environment and cause zero-point drift. Yunnan Observatories has proposed a plan to use optical co-phase detection technology to perform short-period calibration corrections on the zero-point edge sensors. However, atmospheric turbulence affects the frequency of optical co-phase detection, which determines the zero-point calibration correction frequency of the edge sensor.
To determine the zero-point calibration correction frequency of the edge sensor, Yunnan Observatories cooperated with the Nanjing Institute of Astronomical Optics & Technology to research the impact of atmospheric turbulence on optical co-phase error detection. This study was carried out in the active optical experimental system of Yunnan Observatories. It simulated and analyzed the impact of different detection sub-aperture sizes and exposure times on co-phase errors in an atmospheric turbulent environment. The optical co-phase detection technology used in the study is the sub-aperture PSF pattern matching technology. Experimental results show that under conditions of good atmospheric seeing when the detection sub-aperture size is 0.8 times the atmospheric coherence length and the exposure time is no less than 40ms, the optical co-phase detection accuracy is better than 3 nm (RMS). The research results show that under the condition of 10cm seeing and the detection sub-aperture is 80mm, the zero-point calibration correction frequency of the edge sensor can reach more than 10Hz. This research further improved the CGST ring segmented primary mirror scheme, which was published in the famous optical journal Optics Express.
This research was supported by the National Natural Science Foundation of China (No.12273109,11833010) and the Yunnan Provincial Science and Technology Department (No.202105AB160001, 202305AH340002, 202103AD50013).

Contact:
JIN Zhenyu
Yunnan Observatories, CAS
Email: kim@ynao.ac.cn