Prototype of solar ground layer adaptive optics at the 1-m New Vacuum Solar Telescope
The effect of ground layer adaptive optics (GLAO) system for solar active imaging. The GLAO prototype system was integrated into the New Vacuum Solar Telescope (NVST) and saw the first light on January 12th, 2016, with the wavelength of 705.7 nm@0.6 nm. The solar active area NOAA 12480 was imaged without and with GLAO system. It can be seen that GLAO system improved the image quality in large FoV.
Adaptive optics (AO) is an indispensable technique in ground-based solar imaging which provides diffraction limited resolution. However, the traditional AO technique has only a very small corrected field of view (FoV) (~ 10 arcsec), much less than the solar active region which has the typical size of 1~3 arcmin. Multi-conjugate adaptive optics (MCAO) is the most promising technique currently developed to increase the corrected FoV.
The fact that about 60% of the turbulence strength is concentrated in the first few kilometers above the telescope has inspired the concept of ground layer adaptive optics (GLAO). A GLAO system can be seen as a simplified MCAO system. It is equipped with several wavefront sensors to measure the wavefront perturbation introduced by the ground turbulent layer and a single deformable mirror conjugated to a low altitude to compensate for the ground turbulent layer. As opposed to the MCAO, it is important to emphasize that the goal of GLAO is not to attain a near-diffraction-limited correction but to simply reduce the perturbation and stabilize the seeing over a wide FoV.
A solar GLAO prototype was developed and tested at the 1-m New Vacuum Solar Telescope of Fuxian Solar Observatory and saw the first light on January 12th, 2016. The on-sky observational results show that the solar image is apparently improved in the whole 1 arcmin FoV with the GLAO correction. The corresponding results are published in Chinese Optics Letters, Volume 14, No. 10, 2016 (L. Kong, et al., Prototype of solar ground layer adaptive optics at the 1-m New Vacuum Solar Telescope).
Prof. Changhui Rao, the leader of the solar imaging research group of the Adaptive Optics Laboratory, Chinese Academy of Sciences, said the success on the solar GLAO demonstration is an important progress on the AO technique in China, and this will lay the foundation for further development of MCAO.
Based on the GLAO progress, we will concentrate on the solar MCAO research in the next step. The large solar telescopes with MCAO system can be used to monitor the solar activity and acquire the high resolution solar data in real time for the space weather and the solar physics research.