Typical size of solar active region is 1' to 3', using conventional adaptive optics system, only narrow wide field of view (FOV) of around 10″ can be obtained because of restrictions from isoplanatic region. Thus, it is difficult to meet the large FOV high-resolution observation requirements. Ground layer adaptive optics (GLAO) detects and corrects the wavefront distortion in the ground layer turbulence, doesn’t reach near diffraction limit, but it improves the image quality in a wide FOV significantly.

GLAO technology provides solar physicist with a new scientific tool to investigate physics nature and phenomena of solar activity and allows them to achieve more accurate observations. At the same time, it lays a foundation for improving wide FOV multi-conjugate adaptive optics technology.

The GLAO experiment system was developed by RAO’s team in Institute of Optics and Electronics (IOE) CAS and installed in Yunnan Observatory 1 meter New Vacuum Solar telescope. This marks that China's solar adaptive optical technology has made a major breakthrough again. The FOV was increased up to 1'. The team developed a large FOV multi-channel correlation Shack-Hartmann wavefront sensor to detect wave-front inside 1’ FOV and extract wavefront aberrations caused by ground layer atmospheric turbulence. Then the wavefront data was sent to perform closed-loop correction. Ultimately, large FOV high resolution images were achieved, as shown figure 1 and figure 2. Figure 1 shows the images of the activity area NOAA12480, TiO band (center wavelength 7057Å, half-width 6Å) for GLAO open and closed loop. Figure 2 shows the images of the granulation structure of the solar quiet area for GLAO open and closed loop. As can be seen, GLAO image quality over 1’ field of view was enhanced obviously.

The research team led by RAO Changhui successfully captured FOV high-resolution images on sunspots and solar granulation for the first time through the first set of Ground Layer Adaptive Optics (GLAO).

FOV high-resolution images on sunspots and solar granulation (Plotted by ZHANG Lanqiang)

Contact:
ZHANG Lanqiang
E-mail: lqzhang@ioe.ac.cn
Key Laboratory of Adaptive Optics, Chinese Academy of Sciences(http://english.ioe.cas.cn/)