A breakthrough in multi-conjugate adaptive optics (MCAO) made China become the third country to master the solar MCAO technology after United States and Germany. 

Early in 2018, the solar high resolution optical imaging research group from Institute of Optics and Electronics, Chinese Academy of Sciences, led by Rao ChangHui, made breakthrough in MCAO, which will be the key technology in next generation adaptive optics. By connecting its solar MCAO system principle prototype to the 1m new vacuum solar telescope in Yunnan observatory, the group made large field closed-loop correction imaging observation with solar active area, and used the MCAO technology to obtain large field high resolution real-time images of the solar active area, all of this would be the first time happened in China.  

As the solar burst activity will have a great impact on the globe and interplanetary space environment, to avoid the impact of disastrous space weather on human normal activities, and ensure the safety of aerospace engineering, we need to forewarn and forecast the solar activity accurately. In order to study the dynamic origin of solar activity, monitor the space environment and forecast the space weather accurately, it is necessary to obtain large field high resolution observations of solar active area. 

The ground-based large aperture solar telescope equipped with AO system is the main method to conduct high-resolution solar observation. Due to the limitation of atmospheric anisoplanatism, the traditional AO system can’t meet the needs of high resolution observation of the entire solar active area (typical scale: 1 '~ 2' FOV). To solve the problem of small corrected field of view in traditional AO system, MCAO technology has been developed and made great progress in recent years. 

MCAO technology performs 3-D compensation by layered detecting and correcting the wavefront aberration induced by atmospheric turbulence, thus eliminates the effect of atmospheric turbulence over a wide field of view and obtains a near diffraction-limited imaging result. Compared to another large field adaptive optics concept, that is, the ground layer adaptive optics ( GLAO), MCAO corrects the ground surface turbulent wavefront aberrations just like GLAO, besides, it will compensate the upper atmosphere and be able to obtain an image with large field diffraction limit, however, GLAO only detects and corrects the wavefront aberration induced by the ground surface turbulent, which can effectively improve the atmosphere seeing within a large field of view, but the imaging resolution is far less than the diffraction limit of the telescope. 

AS RAO’s team acquiring the high-resolution observations about the solar active area NOAA12683 and comparing it with open-loop data and GLAO system’s closed-loop data, the result shows that a higher resolution imaging observation result of the solar active area can be obtained after corrected by MCAO. 

As an observational subject, breakthroughs in astronomy and development of new astronomical instruments will push forward the astronomy directly and then expand the cognitive scope of human. With the development and application of MCAO, it will help solar physicists see more clearly, finer and more dynamicly when observing the solar activity, deepen the understanding of the stars and even the universe, and provide data support for solar physics research and space weather forecasting. 

The research has been supported by the major scientific research instrument project, 2017 National Natural Science Fund. Next, in order to realize the application of this technology, RAO’s team will provide a dedicated MCAO system to Yunnan Observatory's 1-meter new vacuum solar telescope within 5 years. 

The open loop, GLAO closed loop and MCAO closed loop images of solar active area NOAA12683 observed by RAO’s team (imaging band and bandwidth: 7057@6？). 

(BA Shi)

Contact

CAO Qiang

Institute of Optics and Electronics

Email: caoqiang@ioe.ac.cn