Another national treasure! China's first space telescope - CSST is here

Not long ago, at around 22:30 on July 12, 2022, Beijing time, the current US President Biden released the first batch of photos taken by the Webb Space Telescope, which amazed everyone. This can't help but make people think, does our country have such a powerful space telescope? The answer is of course! In the Changchun Institute of Optics, Fine Mechanics and Physics of the Chinese Academy of Sciences in Changchun, a behemoth about 14 meters high and 20 meters long is under construction. This is the space telescope developed by our country itself - the Chinese Survey Space Telescope (CSST).

"Surveying the sky and looking at a thousand rivers from afar", the word "surveying the sky" in Mao Zedong's poem, such a groundbreaking and imaginative word, has been given new meaning now. In astronomy, surveying the sky is a "census" type of astronomical observation mode that scans the scannable area of ​​the sky piece by piece without distinction. Simply put, it is a full-body CT scan of the universe.

Academician Chen Jiansheng of the National Astronomical Observatory said: "For ground-based sky surveys, we missed the opportunity in the 1980s. Later, the Sloan SDSS telescope in the United States did it, and now the LSST will also start. But optical sky surveys in space have not yet started, and space surveys are too important. Because it can achieve an order of magnitude better image quality than ground-based sky surveys, if there is an opportunity to do space surveys, it means that Chinese astronomy has entered a very remarkable era." As Academician Chen Jiansheng said, space surveys are an important goal of astronomical research in China today. In this golden age of sky surveys, the Chinese must have their own space surveys. In December 2009, during a discussion on the scientific research direction and required experimental equipment of the Chinese space station, the idea of ​​building a large-aperture space optical telescope was first proposed. In March 2012, more than 100 experts from the Space Station Mission Planning Committee reviewed and scored the scientific research projects on the space station, and CSST received priority support from the manned space program. After multiple telescope plans were selected and funding was evaluated, CSST was officially established in November 2013.

Why do scientists put telescopes in the sky? The scientific value far outweighs the cost

The cost and maintenance of space telescopes are much greater than those of ground-based telescopes. Why do we have to pay such a huge price to build them? First of all, ground-based optical telescopes are troubled by the atmosphere. Even at the best ground observation sites, the resolution of telescopes in the optical band is difficult to exceed 0.7 arc seconds. In comparison, most galaxies in the distant universe are only a few arc seconds in size. Many distant galaxies are difficult to distinguish any structure on ground-based telescopes. They look like a few fuzzy pixels, which is far from meeting the research needs of scientists. Space telescopes in a vacuum solve this problem. There is no atmosphere in a vacuum. This idea was boldly proposed by American astrophysicist Lyman Spitzer as early as 1946. It was not until October 4, 1957, 11 years later, that the world's first artificial satellite "Sputnik 1" flew into space. Today, the success of the Webb telescope and the upcoming launch of the CSST have turned people's ideals into reality. They will raise astronomy to a new level and even affect people's communication methods and understanding of the universe.

Sputnik 1 (Image from Baidu Encyclopedia)

What is the mission of the Sky Survey Telescope? Its role cannot be underestimated

Sky survey observation is the most important task of CSST in orbit. In its preliminary plan of 10 years of operation, it is expected to take about 7 years to complete. Similarly, sky survey data processing and corresponding scientific research work are also the focus of research topics. Observational cosmology research requires a large number of extragalactic object samples, so CSST's sky survey observations are mainly in the mid-high galactic latitudes and mid-high ecliptic latitudes where the star density and zodiacal light background are low. In the current mission planning, the CSST sky survey includes four parts: 17,500 square degrees of multi-color imaging observations, seamless spectral observations in the same sky area, 400 square degrees of multi-color imaging deep-field observations, and seamless spectral deep-field observations in the same sky area.

The purpose of conducting such a large-scale sky survey project is nothing more than enriching samples and collecting data. At present, due to the lack of massive observational data, there are gaps in human research in astronomical fields and basic physics such as dark matter and dark energy, large-scale structure of the universe, formation and evolution of galaxies and supermassive black holes, and exoplanets. Without the support of a huge database, it is impossible to provide conclusive evidence to verify the authenticity of relevant theories, nor can it effectively improve the measurement accuracy of parameters, which will hinder the further development of astronomical research. It is believed that large-scale sky survey projects like CSST can alleviate the "urgent need" of data shortage in astronomy and basic physics to a certain extent and promote the development of human science.

What high-tech features does the Sky Survey Telescope have? A well-deserved national treasure

The aperture of the China Survey Telescope is comparable to that of the Hubble Telescope, but its field of view is much larger than that of the Hubble Telescope, 350 times that of the Hubble Telescope, about 1.1 square degrees. The field of view is the range of the sky that the telescope can see. The larger the field of view, the more objects can be observed at the same time. For example, some cameras have a field of view of 60 degrees, while others have a field of view of 70 degrees. The latter can capture a larger range of scenery at the same distance compared to the former. "The Hubble Telescope's field of view is about 1/100 of the size of a fingernail when you stretch your fingers straight. It has been observing the universe for 30 years, but all its data only accounts for a very small part of the night sky," Liu Jifeng, deputy director of the National Astronomical Observatory of the Chinese Academy of Sciences, told reporters. In comparison, the China Survey Telescope is very suitable for surveying the sky and can complete large-scale cosmic observations relatively quickly. In addition, the China Survey Telescope uses an off-axis three-mirror optical system, which greatly improves the detection efficiency and accuracy, and is at the international leading level. The photosensitive element of the China Survey Telescope is also much larger than that of the Hubble Telescope. The biggest feature of China's Sky Survey Telescope is that it will fly with the Chinese space station and move forward together, which makes its maintenance and care easier than the Webb Telescope and the Hubble Telescope.

As an independent module co-orbiting with the Tiangong space station, the Survey Space Telescope is mainly divided into two parts: one is the survey optical facility and the other is the survey platform. The former has a 2m space telescope that can be maintained on orbit, a flagship astronomical project from 2020 to 2030, equipped with survey modules, terahertz modules, multi-channel imagers, integral field spectrometers, exoplanet imaging coronagraphs and other observation terminals.

How is the construction of the Sky Survey Space Telescope going? Let's take a look at the latest progress of CSST

Since its release, the Manned Space Station Project Survey Telescope project has attracted much attention at home and abroad. In the past two years, the research and development of its preparation process and related details have been progressing smoothly. From January 8 to January 10, 2021, the 2020 Annual Summary Seminar of the CSST Scientific Data Processing System was held at the National Astronomical Observatory in a combination of online and offline methods. Nearly 90 development team members from more than 10 units including the National Astronomical Observatory attended the meeting. At this meeting, the backbone personnel of the system development reported on the progress of the development work in 2020, technical verification, current development results, software engineering specifications, etc. The meeting also deployed and arranged the work plan for the next development cycle, laying a solid foundation for the smooth development of the project next year. On April 17, 2021, the CSST Science Work Joint Center and the National Astronomical Observatory Science Center held a plaque unveiling ceremony at the National Astronomical Observatory of the Chinese Academy of Sciences. Liu Jifeng, deputy director of the National Astronomical Observatory, director of the China Space Station Project Survey Telescope Science Work Joint Center, and director of the National Astronomical Observatory Science Center, reported the overall situation of the two centers to all representatives attending the meeting after the unveiling ceremony.

(Photo from Visual China)

On July 18, CCTV.com announced that along with the construction of the Chinese space station, the development of the Sky Survey Space Telescope, which will fly in the same orbit as the station, is also being carried out in an intense and orderly manner. At present, new progress has been made in the development of the prototype of related facilities. The telescope is expected to be launched after the completion of the Chinese space station, and will become a flagship space astronomical facility that leads the world to explore the fantasy universe. In terms of scientific preparation, the manned space program has established a scientific working committee for the Sky Survey Space Telescope, and has established four regional scientific research centers: the Peking University Science Center, the National Astronomical Observatory Science Center, the Yangtze River Delta Science Center, and the Greater Bay Area Science Center. It is reported that the Sky Survey Space Telescope is expected to be put into operation in 2024.

The construction of CSST is the result of the hard work of countless scientific researchers. This huge "cosmic CT scanner" will surely bring astronomy in my country and even the world to a new height. Let us wait and see!

References:

[1] Li Ran. Survey Space Telescope: Will Accompany Tianhe to Explore Space[N]. Guangming Daily, May 13, 2021(16).

[2] Zhan Hu. Large-field multi-color imaging and seamless spectral survey of the manned space telescope[J]. Chinese Science Bulletin, 2021.66(11):1290-1298

[3] Zhang Jingjuan. [EB/OL]. Guanchazhe.com. 2022-07-13-2022-08-03.

[4] Liu Huan. [EB/OL]. China News Network. 2022-07-12-2022-08-03.