Five hundred meter Aperture Spherical Telescope

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Five hundred meter Aperture Spherical Telescope
Location(s) Pingtang County, Guizhou Province, People's Republic of China
Coordinates 25°39′10.5″N 106°51′23.7″E / 25.652917°N 106.856583°E / 25.652917; 106.856583[1]Coordinates: 25°39′10.5″N 106°51′23.7″E / 25.652917°N 106.856583°E / 25.652917; 106.856583[1]
Wavelength 10 cm to 4.3 m[2]:11[3]
Built 2011–2016
Telescope style Deformable fixed primary
Diameter 500 m (physical)
300 m (effective)[2]:12
Collecting area 70000 m2
Focal length 140 m (f/0.466)[2]:12
Dome none
Website fast.bao.ac.cn
External images
Artists' concept of completed FAST

The Five-hundred-meter Aperture Spherical Telescope (FAST) (Chinese: 五百米口径球面射电望远镜), nicknamed Tianyan (天眼, lit. "Heavenly Eye" or "The Eye of Heaven"), is a radio telescope located in the Dawodang depression (大窝凼洼地), a natural basin in Pingtang County, Guizhou Province, southwest China.[4]

Construction on the FAST project began in 2011 and has been completed in July 2016. It is expected to be operational by September 2016.[5] It will be the world's second largest radio telescope (after the Russian RATAN-600, which has a sparsely filled aperture).[2][6] Originally budgeted for CN¥700 million,[2]:49[7] the final price was CN¥1.2 billion (US$180 million).[8]

History[edit]

The telescope was first proposed in 1994. The project was approved by the National Development and Reform Commission (NDRC) in July 2007.[9] A 65-person village was relocated from the valley to make room for the telescope[8] and an additional 9,110 people living within a 5 km radius of the telescope were relocated to create a radio-quiet area.[8][10]

On December 26, 2008, a foundation laying ceremony was held on the construction site.[11] Construction started in March 2011,[7][12] and the last panel was installed on the morning of 3 July 2016.[8][12][13][14]

Overview[edit]

FAST has a fixed primary reflector located in a natural hollow (karst), focusing radio waves on a receiver suspended 140 m (460 ft) above it. The reflector is made of perforated aluminium panels supported by a mesh of steel cables hanging from the rim.

FAST's surface is made of 4450[8] triangular panels, 11 m (36 ft) on a side,[15] in the form of a geodesic dome. Actuators underneath make it an active surface, pulling and pushing on joints between panels, deforming the flexible steel cable support into a parabolic antenna aligned with the desired sky direction.[16]

Above the reflector is a light-weight feed cabin moved by a cable robot using winch servomechanisms on six support towers.[12]:13 The receiving antennas are mounted below this on a Stewart platform which provides fine position control and compensates for disturbances like wind motion.[12]:13 This produces a planned pointing precision of 8 arcseconds.[2]:24[9]:179

FAST is capable of pointing anywhere within ±40° from the zenith.[12]:4 The effective aperture is reduced by vignetting at angles above ±30°.[2]:13

Although the reflector diameter is 500 metres (1,600 ft), only a circle of 300 m diameter is used (held in the correct parabolic shape and "illuminated" by the receiver) at any one time.[12]:3 Thus, the name is a misnomer: the aperture is not 500 m, nor is it spherical.

Its working frequency range of 70 MHz to 3.0 GHz,[17] is covered by 9 receivers,[2]:30 with the 1.23–1.53 GHz band around the hydrogen line using a 19-beam receiver built by the CSIRO as part of the ACAMAR collaboration between the Australian Academy of Science and the Chinese Academy of Sciences.[18]

The chief scientist of the project is Nan Rendong (南仁东),[14] a researcher with the Chinese National Astronomical Observatory, part of the Chinese Academy of Sciences.

Comparison with Arecibo observatory[edit]

Comparison of the FAST (bottom) and Arecibo Observatory (top) dishes at the same scale

The basic design of FAST is very similar to the Arecibo Observatory radio telescope. Both are fixed primary reflectors installed in natural hollows, made of perforated aluminum panels with a movable receiver suspended above. There are, however, three significant differences in addition to the size.[16][19][20]

First, Arecibo's dish is fixed in a spherical shape. Although it is also suspended from steel cables with supports underneath for fine-tuning the shape, they are manually operated and adjusted only for maintenance.[16] It has a fixed spherical shape and two additional reflectors suspended above to correct for the resultant spherical aberration.[21]

Second, Arecibo's receiver platform is fixed in place. To support the greater weight of the additional reflectors, the primary support cables are static, with the only motorized portion being three hold-down winches which compensate for thermal expansion.[16]:3 The antennas are mounted on a rotating arm below the platform.[16]:4 This smaller range of motion limits it to viewing objects within 19.7° of the zenith.[22]

Third, the FAST dish is significantly deeper, contributing to a wider field of view. Although 64% larger in diameter, FAST's radius of curvature is 300 m (980 ft),[12]:3 barely larger than Arecibo's 270 m (870 ft),[22] so it forms a 113° arc[12]:4[dubious ] (vs. 70° for Arecibo.) Although Arecibo's full aperture of 305 m (1,000 ft) can be used when observing objects at the zenith, the effective aperture for more typical inclined observations is 221 m (725 ft).[16]:4

See also[edit]

References[edit]

  1. ^ Location taken from satellite views. Project documents give the location as 25°38′50″N 106°51′21″E / 25.64722°N 106.85583°E / 25.64722; 106.85583, but that appears to be inaccurate by about 500 m to the south.
  2. ^ a b c d e f g h Nan, Rendong (April 2008). Project FAST — Five hundred meter Aperture Spherical radio Telescope (PDF). China-US Bilateral Workshop on Astronomy. Beijing. Retrieved 2016-07-04. 
  3. ^ Harris, Margaret (2009-01-27). "China builds super-sized radio telescope - physicsworld.com". physicsworld.com. Retrieved 2015-10-20. 
  4. ^ "中国"天眼"能不能发现外星人?" [Can Chinese Tianyan find aliens?] (in Chinese). XINHUANET.com. 22 February 2016. 
  5. ^ Rosen, Ben (4 July 2016). "China makes a statement with gigantic, $185-million telescope". The Christian Science Monitor. 
  6. ^ "China starts building world's biggest radio telescope". New Scientist. 8 June 2011. Retrieved 2015-10-19. 
  7. ^ a b Quick, Darren (2011-06-16). "China building world's biggest radio telescope". gizmag. Retrieved 2012-08-13. 
  8. ^ a b c d e "Xinhua Insight: Installation complete on world's largest radio telescope". Xinhua. 3 July 2016. 
  9. ^ a b Jin, C. J.; Nan, R. D.; Gan, H. Q. (2007). "The FAST telescope and its possible contribution to high precision astrometry" (PDF). International Astronomical Union 248: 178–181. doi:10.1017/S1743921308018978. Retrieved 2015-10-19. 
  10. ^ Wong, Edward (17 February 2016). "China Telescope to Displace 9,000 Villagers in Hunt for Extraterrestrials". New York Times. The report said officials were moving 2,029 families, a total of 9,110 people, who live within about three miles of the telescope in the area of Pingtang and Luodian Counties in the southwestern province of Guizhou. Depopulating the area will create "a sound electromagnetic wave environment" for the telescope, Xinhua said. 
  11. ^ "中国科学院·贵州省共建国家重大科技基础设施500米口径球面射电望远镜(FAST)项目奠基" (in Chinese). Guizhou Daily. 2008-12-27. Retrieved December 28, 2008. 
  12. ^ a b c d e f g h Rendong Nan; Di Li; Chengjin Jin; Qiming Wang; Lichun Zhu; Wenbai Zhu; Haiyan Zhang; Youling Yue; Lei Qian (2011-05-20). "The Five-Hundred-Meter Aperture Spherical Radio Telescope (FAST) Project". International Journal of Modern Physics D 20 (6): 989–1024. arXiv:1105.3794. doi:10.1142/S0218271811019335. 
  13. ^ "China completes installation of world’s largest telescope". The BRICS Post. 3 July 2016. 
  14. ^ a b McKirdy, Euan (12 October 2015). "China looks to the stars with creation of world's largest radio telescope". CNN News. Retrieved 2015-10-19. 
  15. ^ "China assembles world's largest telescope in Guizhou". Xinhua. 24 July 2015 – via China.org.cn. 
  16. ^ a b c d e f Williams, R.L. II (July 2015). Five-Hundred Meter Aperture Spherical Radio Telescope (FAST) Cable-Suspended Robot Model and Comparison with the Arecibo Observatory (PDF) (Report). Ohio University. 
  17. ^ "Receiver Systems". FAST Home Page. National Astronomical Observatories, Chinese Academy of Sciences. Retrieved 28 June 2014. 
  18. ^ Strom, Marcus (6 May 2016). "CSIRO technology to be at the heart of the world's largest radio telescope in China". Sydney Morning Herald (Fairfax Media). Retrieved 7 May 2016. 
  19. ^ Jin, Chengjin; Zhu, Kai; Fan, Jin; Liu, Hongfei; Zhu, Yan; Gan, Hengqian; Yu, Jinglong; Gao, Zhisheng; Cao, Yang; Wu, Yang (23 October 2013). The optics of the Five-hundred-meter Aperture Spherical radio Telescope (PDF). Internaltional Symposium on Antennas and Propagation. Nanjing: National Astronomical Observatories, Chinese Academy of Sciences. 
  20. ^ Qiu, Yuhai H. (11 December 1998). "A novel design for a giant Arecibo-type spherical radio telescope with an active main reflector" (PDF). Monthly Notices of the Royal Astronomical Society (Beijing Astronomical Observatory, The Chinese Academy of Sciences) 301 (3): 827–830. doi:10.1111/j.1365-8711.1998.02067.x. 
  21. ^ Cortés-Medellín, Germán (13 September 2010). AOPAF: Arecibo Observatory Phased Array Feed (PDF) (Report). National Astronomy and Ionosphere Center, Cornell University. 
  22. ^ a b "Arecibo: General Statistical Information on Antenna". National Astronomy and Ionospheric Center. 3 January 2005. Retrieved 5 July 2016. 

Further reading[edit]

External links[edit]