The Institute of Optoelectronics successfully developed the first 2m-class solar telescope in China

[ Instrument Network Instrument R & D ] The solar high-resolution imaging technology research team led by Rao Changhui, a researcher at the Institute of Optoelectronic Technology of the Chinese Academy of Sciences, successfully developed a 1.8-meter solar telescope. And spheroid high-resolution images. This is China's first set of 2-meter solar telescopes, and it is also the largest-caliber solar telescope that has been built in the world before the official launch of DKIST, the 4-meter solar telescope in the United States.

The sun is the closest star to the earth. The "mood" of the sun directly affects human activities, especially the large-scale solar eruption will throw electromagnetic radiation and particle radiation to the sun, the earth, and the earth's space, giving ionospheric, magnetic layers and even the atmosphere Brings severe disturbances, affecting ground communications and power supply. Therefore, monitoring and research on solar activity and its space environment impact has always been one of the key directions of attention in countries around the world.

The corona is a thin, faint outer atmosphere around the sun. Its structure is complex. It can only be appreciated during the short period of total solar eclipse, because the light of the sky is always scattered or diffused into the telescope from all sides. . In 1930, the first coronagraph developed by French astronomer Leo was born. This instrument can effectively block the sun, and the scattered light is very small. Therefore, it can successfully take a corona picture on any day when the sun is shining. Since then, the activities of the World Observation Corona have gradually risen.

Internationally, it has been committed to establishing two-meter and larger-caliber solar telescopes. At present, the internationally established 2m-class solar telescopes mainly include the American 1.6m solar telescope GST and the German 1.5m solar telescope GREGOR. The American 4m solar telescope DKIST has not yet officially operated, and the European 4m solar telescope EST has begun designing and developing.

With the support of the National Natural Science Foundation of China and other channels, the research team carried out a series of basic theoretical studies such as photothermal effects, low-contrast extended target wavefront detection, and broke through the thermal control technology of the main mirror of large-aperture solar telescopes and real-time waves under strong turbulence conditions. Key technologies such as front detection technology and large-field solar adaptive optical correction technology have successfully developed a 1.8-meter high-resolution solar telescope. The telescope is equipped with a 451-unit high-order solar adaptive optical system, a ground surface adaptive optical system (GLAO), and a solar multi-band high-resolution imaging system. In the first light observation, the low-contrast extended target of the rice grain structure on the solar surface was used as a beacon, and the GLAO system was used to successfully realize the real-time correction of the surface wave front disturbance. The solar atmospheric photosphere layer G-band (430.5nm) was obtained. High-resolution imaging observations of the two bands of TiO and 705 (705 nm) and the halosphere (656.3 nm) of the solar chromosphere.

Coronagraph is only a type of solar telescope. Since the 20th century, due to the needs of actual observation, various solar telescopes have appeared, such as color ball telescopes, solar towers, combined solar telescopes and vacuum solar telescopes.

The solar tower, also known as a tower telescope, is a basic tool for solar physical observation. The shape is a tower building, usually more than 20 meters high. A ceiling mirror is installed on the top of the tower, which reflects the incident solar light vertically downward and enters the imaging optical system and ancillary instruments. The solar tower is usually built as a double-layer structure. In addition to the ceiling mirror, a solar telescope imaging optical element is placed in the middle, and a large-scale solar spectrograph and other auxiliary instruments are installed in the bottom of the tower or underground shaft.

The vacuum solar telescope puts all imaging optics in a vacuum tube. This telescope can eliminate the harmful effects of airflow inside the instrument on imaging. The most famous vacuum solar telescope is at the Sacramento Peak Observatory. Its shape is a 41-meter-high open-air cone tower with a vacuum-tight turntable on top. After the sun's rays penetrated into the 75 cm diameter glass sealed window, they were reflected by two flat mirrors with a diameter of 110 cm constituting the ground-level system onto the imaging mirror with a diameter of 0.6 m and a focal length of 46 m. ​​The returned light passed through the oblique plane mirror and passed through the sealed The exit window enters the auxiliary instrument. The vacuum cylinder weighs 250 tons and can be rotated. This instrument is installed on a quiet mountain, and can observe the structure of the very small solar surface and the lower atmosphere. The resolution is equivalent to the ability to recognize a car license plate at a distance of 96 kilometers.

The 25th solar activity week has arrived. As the solar activity becomes more frequent, space weather events will become more serious. In the future, the solar telescope will also be equipped with a solar multi-layer conjugate adaptive optics (MCAO) system, a high-resolution magnetic field and velocity field detection system in the solar active area, etc., in order to obtain more comprehensive solar activity monitoring data for the occurrence of solar activity, Development and evolution provide more accurate and detailed observation data, and provide very important data support for solar physics research and space weather forecasting business.

Source: Encyclopedia, Institute of Optoelectronic Technology