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Five-hundred-meter Aperture Spherical radio Telescope (FAST)
Five-hundred-meter Aperture Spherical radio Telescope (FAST) is a Chinese mega-science project to build the largest single dish radio telescope in the world, which aims to build a 500 diameter active reflector radio telescope on a karst depression in Guizhou province, in order to provide large sky-coverage and achieve high sensitivity for astronomical observations. On March 25, 2011, the construction of FAST was commenced. On September 25, 2016, the main structure of FAST was completed as scheduled. Acclaimed as the China Sky Eye, FAST is the world’s largest single-dish and the most sensitive radio telescope with China's own intellectual property rights.
The construction of FAST composes of five systems, including site and earthwork, active reflector, cabin suspension, measurement and control, receiver and observatory.
Compared with the Arecibo 305-m radio telescope, FAST has three outstanding aspects: its site is a deep and round karst depression named Dawodang in Guizhou province, it uses an active reflector to correct spherical aberration, and it has a lightweight feed cabin driven by six cables and a servomechanism plus a parallel robot for closed-loop precision control.
The exquisite sensitivity due to its size is ideal for large-scale surveys. FAST will enable astronomers to get a jumpstart on many science goals — for example, surveying the neutral hydrogen line emission from the distant galaxies out to very large redshifts that would provide significant information on the origin and evolution of the Universe, detecting thousands of new pulsars, that may uncover the law of extreme objects, etc.. Even higher sensitivity can be achieved by joining FAST with the international Very Long Baseline Interferometry network. This system may be able to resolve the fine structures of weak thermal sources, to get a close-up on the origin and evolution of stellar sources, and even to directly image the radio-loud extrasolar systems.
The story of FAST dates back to 1994, with the submission of the initial proposal. It was 2007 before the funding proposal gained approval. In 2011, the building phase of the project commenced. The girder ring of FAST to support the cable-net of reflectors was fully formed in December 2013, and on July 17, 2014, the installation of the cable-net itself followed suit. On 3 July 2016, the last of the 4,600 reflector elements was successfully placed. Meanwhile, the feed support system including six support towers and feed cabin housing the secondary adjustment system were constructed. The hardware and software for the measurement and control systems has been developed to ensure the high precision of astronomical observations. In addition, seven sets of receivers were designed and constructed based on international cooperation, such as the construction of the 19-beam receiver for FAST by the Commonwealth Scientific and Industrial Research Organisation in Australia. In order to protect the radio environment of the FAST site, the local government established a radio quiet zone with a radius of 30 km in 2013. On September 25, 2016, the main structure of FAST was completed after five and a half years of construction. Since then, the telescope has moved into the commissioning and test observation phase.
A single-pixel receiver covering the 270–1,620 MHz band has been designed and mounted at the feed cabin, providing a platform for observations during the early stages of operation. In May, 2018, the 19 beam receiver was installed, and the efficiency of telescope's survey will be greatly improved.
In 2017, FAST functional commissioning was basically completed. FAST has achieved several of observation modes such as pointing, tracking, drift scanning, etc. Reflector surface accuracy and feed pointing accuracy, telescope efficiency have satisfied the needs of scientific observation requirements basically. On October 10, the first discoveries of six pulsars observed by FAST were announced. The first one is numbered as J1859-01(FP1-FAST pulsar #1), with the rotation period of 1.83 seconds, which is estimated to be 16,000 light-years away from the earth. And it was found by drift scanning on the southern sky of galactic plane on August 22 and was confirmed by Parkes telescope on September 12. This is the first time that new pulsars were discovered by China's radio telescope.
On February 27, 2018, FAST first discovered a radio millisecond pulsar (MSP) coincident with the unassociated gamma-ray source 3FGL J0318.1+0252 in the Fermi Large Area Telescope (LAT) point-source list, which was confirmed by the Fermi-LAT team in reprocessing of Fermi data on April 18. The newly discovered pulsar, now named PSR J0318+0253, with a spin period of 5.19 milliseconds, an estimated distance of about 4 thousand light-years, and as potentially one of the faintest radio MSPs. This is another milestone of FAST.
FAST has discovered 59 pulsar candidates in high quality, and 44 pulsars have been confirmed so far (July 16, 2018).
FAST is a large scientific device of which China owns the intellectual property rights independently. It was designed, developed, manufactured and managed by Chinese scientists. A series of key technologies have been developed and a number of technological breakthroughs have been achieved: high strength and high precision large span cable net structure, high performance moving fiber optic cable, and large scale and high precision real-time measurement system, etc., which have promoted scientific and technological progress and industrial upgrades in many high-tech fields in China. FAST’s exclusive innovations hold the important practical values that meet the major demands of our country. It will greatly promote the economic prosperity and social progress in the western region of China.
The receiving area of FAST is equivalent to about 30 football fields. Its overall performance and sensitivity are several times higher than the existing telescopes and it is expected to maintain a leading position in the next 20 years. The innovative engineering concept and design of FAST paves a new road to realize a huge single dish in the most effective way.
FAST will be under commissioning until it reaches the designed specifications and becomes a Chinese national facility.
29th Linear Accelerator CONFERENCE-LINAC18 Jun 27,2018