1933, Karl Jansky of Bell Laboratories accidentally discovered stable electromagnetic radiation from the center of the Milky Way, which marked the birth of radio astronomy. The four major discoveries of modern astronomy-quasars, pulsars, 3K cosmic background radiation and interstellar molecules-are all based on radio astronomy. Among the projects that won the Nobel Prize in Physics, eight involved astronomy, five of which were closely related to radio astronomy. Receiving area is the most important comprehensive performance parameter of astronomical telescope. According to the characteristics, requirements and existing technical strength of astronomy and astronomical observation, the National Astronomical Observatory of Chinese Academy of Sciences put forward the overall engineering concept of building a 500-meter spherical radio telescope (FAST) in China. Its effective receiving area is nearly one order of magnitude higher than the existing and planned world's largest fully movable single-antenna telescope, and it will be the largest single-aperture radio telescope in the world. The formation process of the concept of rapid engineering embodies extensive international cooperation, continuous technological innovation and interdisciplinary. Astronomers from Australia, Canada, China, France, Germany, India, the Netherlands, Russia, Britain and the United States jointly proposed to build a large telescope array (LT) with a receiving area of 1 square kilometer at the International Radio Science Union (URSI) 1993 Kyoto Conference. It accords with the prediction of the comprehensive performance progress of radio telescope according to Livingstone curve (figure 1), and has a clear scientific motivation-the observation of neutral hydrogen at different cosmic distances. "Humans are eager to really take a look at the original universe and understand how the structure of the universe was formed and evolved until now before the radio wave environment was completely destroyed. Only the big radio telescope SKA can help mankind realize this dream. " If we lose this opportunity, we can only build a telescope with the same caliber on the back of the moon, because the background noise of galaxies there is the same.

SKA can be divided into about 30 basic units, each with a diameter of about 200 meters, so as to obtain high resolution and fast imaging capability. From 65438 to 0999, the International SKA Steering Committee (ISSC) was established, and its members included major radio astronomy powers. SKA's 0-level scientific goal is related to almost all astronomical problems. Its large receiving area of 150 football field can extend astronomical observation to the primitive universe, and it does not need the original high sensitivity of time domain and frequency domain integration, making it a camera of transient multicolor universe. ISSC plans to build SKA in 2020, with a total project budget of 654.38 billion US dollars.

SKA not only embodies the imagination of modern science, but also has risks, which is difficult to achieve without extensive scientific and technological cooperation. China's radio astronomy strategy should focus on SKA.

1In April 1994, the National Astronomical Observatory (formerly Beijing Astronomical Observatory) started the SKA site selection work in Guizhou. 1995 10, 10 successfully held the third meeting of the International Large Radio Telescope Working Group (LTWG-3) in Guizhou. 199565438+In February, SKA China Promotion Committee held its founding and the first annual SKA academic conference at the National Astronomical Observatory, and conducted an all-round exploration on Guizhou depression site, various potential or new broadband feeds, platform-free cable support, spherical reflector structure and the overall electrical performance of the antenna. 1In July, 1997, SKA China Promotion Committee put forward the preliminary idea that China independently built the world's largest single aperture spherical telescope (FAST). In April 2000, Fast General Motors held a large-scale international conference in Guizhou (IAU Institute 182).

Besides FAST, there are other engineering schemes to realize SKA, such as ATA in the United States, AAT in the Netherlands, LAR in Canada, Lunenburg lens array and cylindrical mirror in Australia, and PPD in India. It will take some time to realize the decision of SKA's final plan. Whether FAST can eventually become the leading unit of SKA, it will be the largest single-aperture radio telescope in the world, and its leading position in the world will be maintained for at least 20 years. Since 1994, SKA China team has been established with the National Astronomical Observatory as the core, and its members include China Academy of Sciences, Ministry of Education, former Ministry of Electronics Industry, Aerospace Industry Corporation and Guizhou Science and Technology Department. The innovative scheme design, scientific objectives, site, active reflector, feed cable support, antenna overall electrical performance, measurement and control, receiving system and so on of FAST, the leading unit of SKA China engineering concept, are put forward. Conduct research in a multidisciplinary way. FAST's innovative design and rich scientific and technological content have attracted extensive cooperation at home and abroad. In the universities and research institutes engaged in FAST pre-research, there are nearly 50 graduate students who are engaged in related fields, of whom 14 have obtained degrees, and 1 1 is a postdoctoral fellow. Some early participants have grown into academic leaders.

The innovations of FAST project are as follows (Figure 2): Natural karst potholes in Guizhou are used as the site; A spherical cap active reflector with a diameter of 500 meters is laid in the pit, and the irradiated part forms an instantaneous paraboloid with a diameter of 300 meters during observation, and the spherical aberration is corrected on the ground to realize real-time broadband and full polarization; The feed is supported by an optical cable traction mechanism integrating optics, mechanics and electricity, and a secondary stable platform is installed in the feed cabin, so that the telescope can point and track accurately and quickly without rigid connection between the focus and the active reflector.

At the third annual meeting of SKA held in April 1998, the National Astronomical Observatory clearly put forward the concept of FAST project. At the meeting, the FAST Project Committee was established, and the relevant groups composed of more than 20 research units across the country were defined, focusing on the feasibility study of the above key technologies. As the first batch of "major innovation projects", the FAST pre-research project was established on1March, 1999, and was supported by China Academy of Sciences and Ministry of Science and Technology. Under the coordination of the National Astronomical Observatory's Large Radio Telescope Technology Laboratory (FAST Overall Group), various key technology feasibility research projects are progressing smoothly, and passed the acceptance of Chinese Academy of Sciences at the end of 2000/kloc-0.

From SKA China Promotion Committee, FAST Project Committee to FAST overall team, after 10 years, Chinese astronomical and related engineering researchers cooperated sincerely, and with the support of Ministry of Science and Technology, Chinese Academy of Sciences and National Foundation of China, FAST overall team completed the feasibility study of key technologies such as FAST active reflector and feed cable support, and all the key technologies made breakthroughs, without technical risks, and had the conditions to participate in the selection and approval of major national scientific projects.

The innovative design of FAST embodies the independent intellectual property rights of China people, which will improve the overall display of basic scientific research in China and the comprehensive national strength of China. According to incomplete statistics, by the end of 2003, about 280 related research papers had been published, including 6 SCI papers, 30 EI papers, 72 international conference papers, 9 domestic and foreign journals and 4 monographs. The FAST overall group has long-term and stable substantive cooperation with almost all large radio observatories in the world. 1993, convened and presided over various cooperation discussions and key technical consultations with experts from China, Germany, Sweden, the Netherlands, Britain, the United States, Australia and Russia. In 1997, the Ministry of Agriculture signed a technical research plan with five countries to jointly develop future very large radio telescopes: the Netherlands, the United States, Australia, Canada and India. 1999, Beijing Observatory and Jodrell Bank Observatory in Britain signed a memorandum of understanding: FAST cooperation. In 2000, it extended the memorandum of bilateral cooperation with the Netherlands, such as the 2000 joint research proposal: Koninklijke Nederlandse Akademie van Wetenschapp PN. In addition, the cooperation with the Arecibo Observatory in the United States is progressing smoothly (Figure 3); The scheme design of telescope receiving system in focal room has passed. British cooperation is completed; What the hell is going on: China? Dutch, China? Multi-beam cooperation between Australia and phased array.

In London, the FAST team was invited to attend the monthly meeting of RAS to introduce the FAST project to members of 150 (RAS Fellow). At Cambridge University, Hervis, winner of the Nobel Prize in Physics and discoverer of pulsars, participated in the cooperative discussion of the FAST project team for a whole day. Afterwards, he also revised the article of FAST active reflector and recommended it to the famous astronomical magazine MNRAS for publication. Dr. P. Fletcher, director of international cooperation of PPARC, visited the National Astronomical Observatory twice in 1998 and 2000 to learn about the work of FAST and discuss the specific issues of Sino-British FAST cooperation. 1998 10, Professor P. Murdin, Director of PPARC Astronomy Department, Professor A. Lyne, Director of Jodrell Bank Observatory in the UK, Professor P. Wilkinson, Director of MERLIN, and Dr. J. A. Battilana, Chief Engineer, visited China for the first time due to FAST cooperation. Subsequently, four senior feed engineers of Jodrell Bank Observatory, J. A. Battilana, N. Roddis, C. Baines and G. Kitching, conducted a three-month cooperative study on the overall design of the FAST feed cabin, and visited the FAST overall group for one week in February 2000, initially forming a cooperative framework for developing the FAST receiving system between the two observatories.

This kind of international scientific and technological cooperation will enable FAST to have an advanced receiving system that is in line with the international frontier. Derel Bank Observatory and ATNF Observatory are the most successful developers and users of multi-beam feed system. China and Britain are carrying out the joint technical design of the specific configuration of FAST feed cabin, taking into account the requirements of FAST scientific objectives, technical feasibility of feed receiver and preliminary cost estimation. The specific contents include: setting of fast working frequency band, feed types of different frequency bands and their position arrangement in feed cabin, polarization mode, local oscillator and multi-channel system of feed receiver, low noise amplifier (LNA), selection of refrigerator and reasonable configuration of pre-vacuum system, real-time monitoring system of refrigerator and receiver, signal (optical fiber) transmission, power supply of fast feed cabin, operation and maintenance of feed receiver, high-precision measurement and positioning system, astronomical instruments and equipment in main control room, etc.

The British side also provides technical advice and support for FAST design, such as the design of FAST active spherical reflector, feed support, overall electrical performance and electromagnetic compatibility of the antenna. And carry out scientific and technological cooperation through personnel exchange visits, bilateral technical seminars and joint development. From 200 1, the British side cooperated to train doctors in electronic engineering of feed receiver for FAST. In addition, if FAST can be officially started, the British side will provide funds to jointly complete the construction of the multi-beam feed receiving system with China. China, on the other hand, provided part of the FAST observation time for Britain to conduct world-class astronomical research.

SKA has become a large-scale radio astronomy project coordinated by OECD MSF, providing a platform for international exchange and technical cooperation for FAST project. 1From May to June, 1998, astronomers from the Netherlands Astronomical Research Foundation (NFRA) and the University of Amsterdam, Professor R Strom, and the world's number one antenna master, Professor S von Hoener from Germany, were invited to visit the National Astronomical Observatory to discuss the scientific objectives and technical scheme of FAST with relevant experts.

By the end of 2003, FAST had made nine special reports at large international conferences. Science reported the progress of FAST pre-research three times in 1995, 1998 and 2002. In 2003, the Ministry of Science and Technology approved the launch of "Key Project of International Science and Technology Cooperation": 1 square kilometer array SKA international cooperation.