Building a Dream "Space Home" - A History of China's Space Station Construction
"Flying giant eyes", made in China!
A number of international mainstream media have forecasted the world’s hotspot science and technology events that may occur in 2023, including the China Space Station Engineering Survey Telescope ("China Sky Survey Space Telescope", English abbreviation "CSST"). It will become a new annual milestone for human exploration or use of space with the launch of new rockets by the United States and the launch of asteroid mining missions.
According to the latest version of the China Aerospace White Paper, after the Tiangong Space Station is fully completed, my country will launch and deploy CSST in due course to carry out more extensive astronomical surveys.
The China Manned Space Engineering Office has stated to the outside world that my country's first large-scale sky survey space telescope is planned to be launched in 2023 to carry out wide-area sky survey observations, and will conduct research on the formation and evolution of cosmic structures, dark matter and dark energy, exoplanets and solar system celestial bodies. Carry out cutting-edge scientific research.
Rising star in the field of space optical observation
When it comes to astronomical telescopes, the first thing many people think of is the "Chinese Sky Eye", the 500-meter Aperture Spherical Telescope (FAST) located in Pingtang, Guizhou.
As a major scientific and technological infrastructure built in my country in recent years, FAST has gained high popularity and is well-known at home and abroad for its large scale, excellent exploration capabilities and fruitful initial detection results.
Compared with FAST, although CSST is not so well-known at present, for the industry insiders, it is a rising star in the field of astronomical observation with optical telescopes.
There are of course many differences between FAST and CSST in addition to their popularity. The most fundamental difference is that they belong to different types of astronomical telescopes.
FAST is a radio telescope that receives radio waves from celestial bodies, and the giant spherical mirror is its antenna for receiving radio waves. It collects weak cosmic radio signals and transmits them to the receiving system for amplification. The receiving system separates them from noise Useful signals are sent out and sent to the back-end computer for recording.
The results recorded by the computer are displayed as many curves for astronomers to study and analyze to obtain various cosmic information.
Because radio waves can penetrate space, radio telescopes are less affected by light and climate, and can work around the clock and without interruption.
CSST is an optical telescope that captures near-ultraviolet to visible light bands. Through the objective lens with large diameter and long focal length and the eyepiece with small diameter and short focal length, it can realize close-up imaging of distant objects.
In this way, people can observe very distant celestial bodies through optical telescopes.
Due to comprehensive factors such as the earth's thick atmosphere, ionosphere, ozone layer and geomagnetic field, the observation capabilities of ground-based optical telescopes are limited.
With the advancement of aerospace technology, space optical telescopes that eliminate the influence of the above factors have emerged as the times require. This is the Hubble Space Telescope and the Webb Space Telescope, which were launched in April 1990 and December 2021, respectively.
The China Sky Survey Space Telescope will follow closely behind and become the new "giant flying eyes" of mankind.
Divided into two parts, with 5 major equipment
CSST will be a super-large space vehicle. Regarding its specific size, Liu Jifeng, director of the China Space Station Engineering Sky Survey Telescope Scientific Work Joint Center and deputy director of the National Astronomical Observatory, once described it this way: "The size is equivalent to a bus. Standing up to 3 The height of the building is 2 meters, and the diameter is 2 meters." Judging from the information disclosed so far, the total length of the survey space telescope is about 14 meters, the maximum diameter is about 4.5 meters, and the emission mass is about 16 tons.
Zhan Hu, the responsible scientist of the CSST sky survey optical facility and a researcher at the National Astronomical Observatory of the Chinese Academy of Sciences, said that CSST is mainly divided into two parts, the "platform segment" and the "optical facility segment". The former is actually the "resource module" of CSST, which is responsible for providing power for its space flight , the latter is the main load of CSST, including five observation equipment, namely sky survey module, terahertz module, multi-channel imager, integral field spectrometer and exoplanet imaging coronagraph.
As its name indicates, the main mission of CSST is "Sky Survey Observation", that is, to conduct a census of celestial bodies. It can clearly and finely observe thousands of galaxies and bring a panoramic high-definition picture of the universe. Therefore, the telescope The most important observation time is the sky survey module.
According to Zhan Hu, the "sky survey observation" accounts for about 70% of CSST's running time.
According to Li Ran, a researcher at the National Astronomical Observatories of the Chinese Academy of Sciences, in order to ensure the imaging quality of the "sky survey observation" and to be able to receive information from a wide field of view, the CSST sky survey module has installed 30 detectors with a total of 2.5 billion pixels.
Among them, 18 detectors are equipped with different optical filters, which makes it possible to obtain images of cosmic celestial bodies in different wavelength bands, leaving a colorful appearance of the universe; the other 12 detectors are used for seamless spectral observation, each time Exposure can obtain spectral information of at least 1000 celestial objects.
During the entire sky survey cycle, the sky survey module will cover 40% of the entire sky area, accumulating high-quality data of nearly 2 billion galaxies.
Zhan Hu and Li Ran introduced CSST's super "sky survey and observation" capabilities, while emphasizing that its fine observation capabilities are also very strong.
The terahertz module, multi-channel imager, integral field-of-view spectrometer and exoplanet imaging coronagraph equipped with the telescope are all precision measurement modules. They will rely on their respective characteristics to carry out exoplanet detection and space-resolved spectral observations in the core region of galaxies. , neutral carbon research in neighboring galaxies, super deep-field observations of the universe and many other characteristic scientific observations.
More suitable for sky survey, easy to maintain and upgrade
As a space optical telescope, what are the characteristics of CSST compared with Hubble Telescope?
In this regard, Zhan Hu replied that CSST is more suitable for sky surveys. The lens diameter of its sky survey camera is 2 meters, although it is slightly smaller than the Hubble Telescope's about 2.4 meters, but its field of view is about 300 times that of the Hubble Telescope, which can be compared Quickly complete large-scale cosmic observations.
Li Ran made a vivid analogy: It’s like there is a flock of sheep on a mountain, and the Hubble Telescope can see one sheep, but CSST can take pictures of thousands of sheep, and the clarity of each sheep is as high as that of Habble. as seen through the telescope.
CSST's sky survey expertise can be said to be "innate".
As the flagship project of my country's manned space station, CSST is the largest space astronomy infrastructure in my country so far. At the beginning of the project design, it aimed at the direction of large field of view, high image quality, and broadband.
In this regard, Li Ran explained that the Hubble Telescope is the pioneer of human space telescopes and has achieved fruitful scientific research results. Only by adopting a different innovative design can CSST further promote the development of space astronomy and further expand the boundaries of human cognition.
There are two options for innovative design ideas: one is to build a space telescope with a larger aperture to see deeper and obtain information on fainter celestial objects; High-efficiency sky survey observation, more systematic study of space.
Relevant parties in China chose the second way of thinking for CSST based on relevant actual conditions.
Another notable feature of CSST is that it complements the space station.
From the Chinese full name of CSST "China Space Station Engineering Sky Survey Telescope", we can see the close connection between the two.
Specifically, CSST takes the Tiangong space station as its space home port, and usually stays away from the space station and flies independently in the same orbit with it when observing. It can operate normally within the 1-year lifespan, effectively avoiding the situation that the Hubble Telescope has failed for about 3 years and cannot be repaired, and can extend the life in orbit and achieve extended "service".
It has been continuously adjusted and improved for more than 10 years
CSST is the result of long-term cooperation between Chinese scientists, especially experts in the fields of optics and astronomy and aerospace science and technology workers.
Zhan Hu introduced that in December 2009, the headquarters of the China Manned Space Engineering Space Application System organized a series of seminars to discuss the scientific goals and research directions of the space station in the fields of microgravity science, astronomy, life science, and earth science. This kicked off the prelude to the CSST project.
In November 2013, CSST was formally established.
Zhan Hu specifically pointed out that according to the plan when the project was approved, the CSST was directly connected to the space station's experimental module, but this caused some problems.
For example, attitude changes, structural deformations, and disturbances caused by various vibration sources of the space station assembly will seriously degrade the image quality of staring observation.
For another example, factors such as the polluted environment and particulate matter that may exist around the space station, the roughly oriented attitude of the space station to the ground and the restrictions on the observation direction by the structure of the space station, and the stray light generated by the surfaces of the cabin and solar panels are all unfavorable for astronomical observations. .
In view of this, in 2015, the program was adjusted to co-orbit independent flight of CSST and the space station and was approved.
After selection, five instruments including the sky survey module and terahertz module equipped by CSST were determined.
In April 2022, the development of the first sample of CSST entered a critical period.
At the end of the year, the development of the first sample identification part was completed.
According to Xu Shuyan, the overall chief designer of the Xuntian optical facility and a researcher at the Changchun Institute of Optics and Mechanics of the Chinese Academy of Sciences, after completing the integration test work of the telescope's subsystems, components, and units, he will immediately transfer to the development of the prototype and the flight parts, and then cooperate with Xuntian. The platform is integrated to carry out joint tests, launch site tests, and finally choose an opportunity to launch.
While the CSST development and other work are in full swing, the observation data processing preparation work has already started to advance.
According to Li Ran, CSST will produce 50PB of scientific data products in the whole cycle. The relevant departments have established a team composed of astronomers, data experts and computer experts to devote themselves to the development of CSST scientific data processing system, and produce products for the whole country and even the whole world. Astronomical images and star catalogs used by astronomers around the world for further research.
It is expected to make important contributions to the development of world astronomy
CSST has not yet launched into space, but the advanced space observatory open to the world it is committed to building will provide new possibilities for human beings to understand the world, and has attracted the attention of scientists around the world, especially astronomers and physicists.
On the website of the CSST Joint Center for Scientific Work, people can see the seven major scientific goals that CSST aims at, including cosmology, galaxies and active galactic nuclei, the Milky Way and neighboring galaxies, stellar science, exoplanets and solar system objects, etc., each All items point to the forefront of contemporary science.
For example, using the rich observational data provided by the CSST large sky survey and ultra-deep field observations, to study the accelerated expansion of the universe, dark energy, dark matter, etc., to study the morphology and structure of galaxies and their evolution, active galaxies and supermassive black holes, etc. .
Li Ran said that CSST is expected to help humans explore and answer basic questions about the material composition, structure, and evolution of the universe.
Zhan Hu pointed out that the improvement of astronomical detection capabilities has promoted human cognition of the universe. Every breakthrough in observation depth, breadth, wave band, and photometry accuracy will bring major discoveries and even lead to revolutionary developments in astronomy and physics.
CSST has excellent comprehensive performance, greatly surpassing previous projects in some indicators, and has the best image quality among sky survey projects in the same period, and its observation ability in the near ultraviolet band is unique.
Li Ran said with full confidence that CSST is not only expected to make breakthroughs in the study of the mechanism of the accelerated expansion of the universe, but also will open up a wider space for discovery and make important contributions to the development of world astronomy.
Zhang Baoshu