page_title: Five-hundred-meter Aperture Spherical Telescope
section_title: Overview
hierarchical_section_title: Five-hundred-meter Aperture Spherical Telescope / Overview
caption_attribution_description: English: Bottom view from one of the six support towers
context_page_description: The Five-hundred-meter Aperture Spherical radio Telescope, nicknamed Tianyan, is a radio telescope located in the Dawodang depression, a natural basin in Pingtang County, Guizhou, southwest China. It consists of a fixed 500 m diameter dish constructed in a natural depression in the landscape. It is the world's largest filled-aperture radio telescope, and the second-largest single-dish aperture after the sparsely-filled RATAN-600 in Russia.
  It has a novel design, using an active surface made of metal panels that can be automatically tilted to help change the focus to different areas of the sky. The cabin containing the feed antenna suspended on cables above the dish is also able to be automatically moved using winches in order to steer the instrument to receive signals from different directions. It observes at wavelengths of 10 cm to 4.3 m.
  Construction on the FAST project began in 2011 and it achieved first light in September 2016. After a three-year testing and commissioning period it was declared fully operational on 11 January 2020.
  The telescope made its first discovery of two new pulsars in August 2017.
context_section_description: FAST has a fixed primary reflector located in a natural sinkhole in the landscape (karst), focusing radio waves on a receiving antenna in a "feed cabin" 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 triangular panels, 11 m (36 ft) on a side, in the form of a geodesic dome. 2225 winches located underneath make it an active surface, pulling on joints between panels, deforming the flexible steel cable support into a parabolic antenna aligned with the desired sky direction.
  Above the reflector is a light-weight feed cabin moved by a cable robot using winch servomechanisms on six support towers.  The receiving antennas are mounted below this on a Stewart platform which provides fine position control and compensates for disturbances like wind motion.  This produces a planned pointing precision of 8 arcseconds.
  The maximum zenith angle is 60-degree when the effective illuminated aperture is reduced to 200 m, while it is 26.4-degree when the effective illuminated aperture is 300 m without loss.
  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.  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, with the upper limit set by the precision with which the primary can approximate a parabola.  It could be improved slightly, but the size of the triangular segments limits the shortest wavelength which can be received.  This range is covered by nine receivers under the feed cabin, 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.
  The Next Generation Archive System (NGAS), developed by the International Center for Radio Astronomy (ICRAR) in Perth, Australia and the European Southern Observatory will store and maintain the large amount of data that it collects.
caption: One of six support towers for the feed cabin
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