Related scientific and technological concepts of 500-meter spherical radio telescope

Light and radio and television signals are electromagnetic waves that travel at the speed of light, and the difference is only in wavelength. For thousands of years, human beings have only observed the universe through the visible light band, but in fact the radiation of celestial bodies covers the entire electromagnetic wave band. Similar to microwave antenna for communication, radio astronomical telescope usually consists of three main parts: the reflecting surface for collecting electromagnetic waves, the receiver for collecting signals and the pointing device. Electromagnetic wave (also known as electromagnetic radiation) is an electric field and a magnetic field that oscillate in the same phase and are perpendicular to each other. It moves in the form of waves in space, and its propagation direction is perpendicular to the plane formed by electric field and magnetic field, effectively transmitting energy and momentum. Electromagnetic radiation can be classified by frequency, from low frequency to high frequency, including radio waves, microwaves, infrared rays, visible light, ultraviolet rays, X rays and gamma rays. The wavelength of electromagnetic radiation that human eyes can receive is about 380 to 780 nanometers, which is called visible light. Any object with a temperature higher than absolute zero can emit electromagnetic radiation, but there is no object with a temperature equal to or lower than absolute zero in the world.

In order to realize the leap-forward development, Chinese astronomical circles proposed to build the world's largest single-aperture radio telescope-500-meter spherical radio astronomical telescope (FAST). It has three independent innovations: using natural karst caves in Guizhou as venues; Thousands of units are laid in the pit to form a 500-meter spherical cap active reflector; The high-precision positioning of telescope receiver is realized by using optical cable traction mechanism and parallel robot. Brand-new design ideas, coupled with the unique advantages of the site, quickly broke through the 100-meter work of the telescope.

The limitation of scope has created a new model for building giant radio telescopes. As a multidisciplinary basic research platform, FAST has the ability to extend neutral hydrogen observation to the edge of the universe, observe dark matter and dark energy, and find the first generation celestial bodies. About 7000 pulsars can be found in a year to study the material structure and physical laws in extreme States; It is hopeful to find strange stars and quark busters; The discovery of neutron star-black hole binary does not depend on the model to accurately determine the mass of black hole; Detecting gravitational waves by accurately measuring the arrival time of pulsars; As the largest station, join the international very long baseline network to image the ultra-fine structure of celestial bodies; It is also possible to find a giant maser galaxy with a high red shift and realize the first observation breakthrough of methanol maser outside the milky way; Used to search and identify possible interstellar communication signals, search for extraterrestrial civilization and so on.

The extended neutral hydrogen region (HI region) is an interstellar cloud composed of neutral hydrogen atoms. These areas are not bright, but they will radiate 2 1 cm (1, 420MHz). The probability of this spectral line is very low, so a large number of hydrogen atoms are needed to see this spectral line. When there is a free zone ahead, the HI region will collide with the expanding free gas (such as ionized hydrogen region). As long as the free zone reaches 10 (that is, one ten thousandth) of the HI region, the emitted light will be brighter than the 2 1 centimeter wave.

Describing the radiation of HI by radio telescope is a technique to measure the spiral arms of spiral galaxies, and it can also be used to describe the gravitational disturbance caused by the interaction between galaxies. When two galaxies collide, the material pulled out like a rope enables astronomers to measure how the galaxies move.

FAST has important application value in the major national demand. Extending China's space TT&C capability from geosynchronous orbit to the outer edge of the solar system will increase the downlink rate of deep space communication data by 100 times. The measurement accuracy of pulsar arrival time has been improved from the current 120 nanoseconds to 30 nanoseconds, making it the most accurate pulsar timing array in the world and making pulsar clocks for the prospective research of autonomous navigation. Carry out high-resolution microwave patrol, diagnose and identify weak spatial signals with a resolution of 1Hz, and serve national security as a passive strategic radar. As a "meridian project", the receiving system of incoherent scattering radar provides high resolution and high efficiency ground observation; Tracking and detecting coronal mass ejections serve the space weather forecast.

FAST research involves many high-tech fields, such as antenna manufacturing, high-precision positioning and measurement, high-quality radio receiver, sensor network and intelligent information processing, ultra-wideband information transmission, mass data storage and processing, etc. The key technical achievements of FAST can be applied to many related fields, such as large-scale structural engineering, high-precision dynamic measurement within a kilometer, development of large industrial robots and multi-beam radar devices. The construction experience of FAST will have an impact on the development of China manufacturing technology in the direction of informationization, limitation and greening.

With FAST, the remote and isolated karst mountain area in southern Guizhou will become a world-renowned international astronomical academic center and a new window to show Guizhou to the world. The astronomical popular science base with FAST as the main body will promote the popular science work in western China and even the whole country, educate young people, publicize the public and decision makers, and serve the long-term strategic goal of rejuvenating the country through science and education. The radius of the active reflector is -300m, the aperture is -500m, the spherical cap opening angle is1120, the effective illumination aperture is Dill=300m, the focal ratio is 0.467, the zenith angle is 40, and the working frequency is 70MHz-3GHz.

(L-band) A/T-2000 m2/K T-20K resolution (L-band) 2.9 ′ multi-beam (L-band) 19 observation switching time < 10min pointing accuracy 8 "FAST pre-research duration 13 years, hosted by the National Astronomical Observatory of Chinese Academy of Sciences, from more than 20 countries. It has been supported by the first batch of major projects, important directional projects and key projects of the National Natural Science Foundation of China. FAST has five key technologies, including site evaluation of karst depression in Guizhou, active reflector, feed support system with optical, mechanical and electrical integration, high-precision measurement and control, receiving system and so on. , all of which have been analyzed, demonstrated and model tested.

On July 10, 2007, the National Development and Reform Commission agreed in principle to include the FAST project in the National High-tech Industry Development Project Plan (documentNo. Development and Reform High-tech 2007 1538), and requested that the feasibility study be carried out promptly and a feasibility report be submitted when conditions permit.