Recently, Zhou Jianping, chief designer of China's manned space project, said that the mainland plans to launch China's first space telescope in 2023 or 2024, which will provide a very powerful observation means for the mainland to understand the universe and understand space. So, what are the characteristics of the space telescope that the mainland will launch? Compared with some foreign space telescopes, what is the difference? The relevant articles of experts such as Zhan Hu and Hao Lei of the Chinese Academy of Sciences have unveiled the mystery for us.
Aerial view of the optical capsule of the Sky Survey
Fill the gap in domestic observation
With advances in adaptive optics technology, ground-based telescopes can correct for the effects of atmospheric turbulence, and good image quality can be obtained through real-time compensation. Despite this, adaptive optics still does not perfectly correct the effects of atmospheric turbulence, and the atmosphere absorbs radiation in the infrared and other bands, which is not ideal. The space telescope can better solve the impact of these problems, and has the advantage that ground-based telescopes cannot match.
China's large-scale astronomical observation facilities started late, and the 4-meter-aperture Guo Shoujing telescope is already the largest telescope in China, and the 12-meter aperture astronomical telescope in the demonstration has yet to be built. The rapid development of China's aerospace technology has also provided the possibility for the mainland to "overtake in curves" in space astronomy.
The 4-meter-aperture Guo Shoujing telescope is currently the largest telescope in China
On September 25, 2010, the mainland space station project was officially approved by the State Council. The entire space station consists of a core module and two experimental modules. Among them, the experimental module II will be equipped with a 2-meter aperture sky survey space telescope.
Such a design scheme makes the space telescope pointing on the space station subject to the influence of the space station structure, and cannot be freely pointed to any direction like an independent space telescope, nor can it be continuously exposed to one direction for a long time.
The design of placing the space telescope in a cabin also severely limits its observation time. Compared with the Euclid Space Telescope and the Roman Space Telescope in Europe and the United States, the observable time of the Chinese Sky Survey Telescope is about half of their time. To this end, the researchers have proposed a plan to put the telescope outside the capsule for observation, but as long as the telescope is directly connected to the space station, the attitude change of the space station, the deformation of the structure, and the vibration caused by the astronaut activity and the docking of the spacecraft will lead to serious degradation of the imaging quality.
In 2015, a new plan was proposed, namely the construction of a separate space telescope, which is the currently planned Sky Survey optical module. It will operate in common orbit with the Chinese space station, on the one hand, avoiding the impact of the space station on the telescope's field of view, observation time and imaging quality; on the other hand, it is convenient to dock the space station for on-orbit maintenance. At the same time, the on-orbit docking maintenance program of the sky survey module is more convenient than the Hubble telescope maintained by the space shuttle, and the maintenance cost is much lower.
The design concept is the first in the world
The optical module of the Sky Survey will be designed for long-term autonomous flight, and will be dominated by high-angular resolution sky survey and spectral sky survey, and its performance is also one of the few in the world's space telescopes.
The Sky Survey optical capsule houses a large telescope with a 2-meter aperture, which is smaller than the 2.4-meter aperture of hubble in the United States, but larger than the 1.2-meter aperture of the Euclid telescope.
The sky survey optical module has an observation wavelength range of 255 to 1000 nanometers, covering the range from near ultraviolet and visible light to near infrared wavelengths, while the Euclid telescope only covers visible and near infrared wavelengths. At the same time, the Sky Survey optical capsule is designed for sky surveying, and its effective field of view is about 1.1 square degrees, which is larger than the Euclid telescope and the Roman telescope, and it is about 300 times the effective field of view area of the Hubble telescope.
In terms of angular resolution or image quality, the telescope of the Sky Survey optical module can reach up to 0.15 arcseconds, which is far superior to the Roman telescope and euclid telescope, and not far from the Hubble telescope's 0.1 arcsecond.
It is worth mentioning that the Optical Module of the Sky Survey pursues high pointing accuracy and platform stability in design, and it surpasses hubble's successor, the Weber Space Telescope, in terms of ultra-static, ultra-fine and ultra-stable platform design indicators.
The Sky Survey optical module surpasses the Webb Space Telescope on a number of metrics
The Sky Survey optical module will not only fill the gap in continental space astronomical observations, but also achieve a field of view close to hubble and two orders of magnitude beyond hubble, and can quickly complete large-scale multicolor imaging and seamless spectral surveys.
The superiority of the optical cabin of the Sky Survey is inseparable from the innovative design. In addition to the 2-meter-diameter Cook type off-axis three-reflection optical system, the optical chamber also adds a folding mirror to facilitate switching between different optical loads, focus adjustment and precision image stabilization.
Among them, off-axis triple reflection is a very good optical design, which is not only conducive to achieving a large field of view, but also does not have the inevitable optical path occlusion in the coaxial reflective optical system of Hubble and Weber telescopes, has the advantage of high light transmission efficiency, and there is no diffraction problem caused by mirror support, and the optical imaging quality is higher. Therefore, the sky survey optical module will also be the first space telescope on the mainland to use active optics, and the imaging quality of the telescope can be further improved by actively adjusting the deformation of the secondary mirror.
In addition, the sky survey optical module can not only fly autonomously, with high attitude adjustment accuracy, but also has the ability to actively rendezvous and dock at the space station. It can receive propellant replenishment while it is docked at the space station, and maintain, repair and update equipment. Compared with the Hubble telescope to launch the space shuttle every maintenance, the common orbit flight and space station maintenance design of the Sky Survey optical module have better maintenance efficiency and cost-effectiveness ratio.
In addition, the optical module also has both sky survey and ground survey capabilities, and can be used as a remote sensing satellite, which is the world's first design concept.
Look forward to making big discoveries
According to the plan, the optical module of the Sky Survey and the space station fly in common orbit, mainly for the implementation of astronomical observations, taking into account the earth observation capabilities. It is capable of providing a survey observation capability that is roughly comparable to hubble resolution, but with a field of view more than 300 times larger, and the performance of optical systems is also one of the few in the world's new generation of space telescopes.
In addition, the sensor of the optical module can also be remarkable, it is equipped with sky survey camera, integrated field of view spectrometer, multi-channel imager, exoplanet imaging corona, terahertz receiver and other 5 payloads, in addition to having basic rapid sky survey capabilities, exoplanet imaging corona also increases the ability to detect and study exoplanets.
Sky Survey optical module docking Chinese space station imagination map
The most important task of the sky survey optical module is sky survey observation, and the researchers plan to conduct multicolor imaging observations of 17500 square degrees, as well as seamless spectral observations of the same sky region, and will also carry out 400 square degrees of multicolor imaging deep field observations and seamless spectral deep field observations of the same sky region.
To put it simply, the optical module of the Sky Survey will conduct census observations such as large-area multicolor imaging sky survey and large-area seamless spectral sky survey in 10 years after the last day, and then conduct a detailed investigation of the selected sky area through the extremely deep multi-color imaging sky survey. Therefore, as the continent's flagship space observation device for the next 10 years, it will observe the gravitational lensing effect and large-scale structure in cosmology through the data obtained from 10 years of sky surveys, and study the dark matter and dark energy in the universe.
In addition, it will also study the formation and evolution of cosmic objects through observations of galaxies and active galactic nuclei, as well as nearby universes and stars, and will also be used to observe and study Cepheids to improve the accuracy of distance measurements at the cosmic scale. It can also be used for the observation of a large number of small and dark objects in the solar system, as well as for observation and research of temporary sources.
In short, the sky survey optical module will not only fill the gap of the continental large space telescope, but also the performance indicators will surpass the previous sky survey project, the imaging quality is the best in the space telescope of the same period, and has a unique near-ultraviolet observation capability. In the next 10 years of sky survey observation missions, the optical module of the sky survey is expected to observe, analyze and reveal the mechanism of accelerated expansion of the universe with excellent performance, resulting in unexpected major scientific discoveries.
Source/ China Aerospace News official WeChat public account
Text/Nemo
Editor/Yang Sishuang
Audit/Yang Jie
Executive Producer/Xu Chunmei
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