Ground-layer adaptive optics for the New Vacuum Solar Telescope: Instrument description and first results

Ground-layer adaptive optics (GLAO) has shown its potential for use in solar observation owing to its wide field-of-view (FOV) correction. A high-order GLAO system that consists of a multiple direction Shack-Hartmann wavefront sensor (WFS), a real-time controller with a multi-CPU processor, and a 151-element deformable mirror was developed for the 1-m New Vacuum Solar Telescope at Yunnan Observatories, Chinese Academy of Sciences. A hexagonal microlens with 9 x 8 subapertures is employed in the WFS. The detection FOV is 42 '' x 37 '', in which 9 (3 x 3) guide regions are extracted for multiple direction wavefront sensing with a frame rate of up to 2200 Hz. To our knowledge, this is the first professional solar GLAO system used as a regularly operating instrument for scientific observations. Its installation and adjustment were performed in the summer of 2021. In this article, a detailed account of the GLAO system and its first light results and a comprehensive analysis of the performance of the GLAO system are provided. The results show that this system can effectively improve the imaging quality after compensating for the wavefront aberration due to ground-layer turbulence.