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Its predecessor to the title was pretty awesome too! Since its completion in 1963, the Arecibo Observatory in Puerto Rico, with a diameter of 305 m (1,000 ft) and a collecting area of 73,000 square metres (790,000 sq ft), had been the largest single-aperture radio telescope ever constructed. The new radio telescope, based in Guizhou Province in southern China and due to be completed within the next couple of years, will be able to see more than three times further into space and survey the skies ten times faster than Arecibo. With its 500 metre diameter, the $102 m facility will boast a collecting area equal to 30 football fields.

Construction was started on FAST in 2009, and is set to take a mere 5.5 years. It will allow astronomers to detect galaxies and pulsars at unprecedented distances. Although vast, the sensitivity required for such a delicate instrument, picking up the faintest of signals from the deepest recesses of space, places extreme demands on its location.

A suitable and unusually radio-quiet site was found some 170 km by road from the provincial capital Guiyang, near the village of Dawodang in a natural valley similar to the one at Arecibo - which permitted the minimum amount of steel construction to support the rim of the bowl. Nan Rendong, FAST chief scientist and a researcher from the National Astronomical Observatories at the Chinese Academy of Sciences, said that, like Arecibo, the natural karst depression mimics the shape of the collecting surface, simplifying the support structure and shielding the telescope from stray human-generated radio waves.

The remote site also makes possible long, uninterrupted observations which, when coupled with the telescope's huge size, gives it twice the sensitivity of Arecibo. Researchers expect to be able to detect objects like weak, fast-period pulsars, too faint to be measured accurately by smaller instruments, with "one of the prizes being the possible discovery of the first pulsar outside the Milky Way," says Nan.

BENTLEY'S INVOLVEMENT
BIM was a significant feature of the technology used to design and build FAST, which depended on close collaboration, from site selection to design and construction, between the Beijing Building Construction Research Institute, Beijing Institute of Architectural Design, and National Astronomical Observatories. Bentley technologies were used extensively, with the contractors deploying BIM technology in the form of AECOsim Building Designer, MicroStation, Bentley Navigator, ProjectWise and ProSteel.

FAST DIMENSIONS
The massive structure's cable net structure consists of 6,670 main cables and 2,225 downhaul cables, with the weight of the cable wheel alone being 216 tons. The reflector consists of 4,600 reflector units installed on the cable net.

The net is strung from a circular ring of supporting pylons, the natural shape of the karst valley optimising the size of each. The use of BIM enabled the clients to save a considerable amount of money, with, for instance, ProSteel and BIM's parameterised technique enabling the teams to design and optimise the 445 network cable nodes, cutting the cost by CNY 4 million.

Even more significantly, the use of Bentley's advanced structural engineering and analysis tools enabled the design and placement of structural components to be achieved with millimetre accuracy.

FAST IN OPERATION
FAST is designed to be flexible. A system of motors attached to its 4600 panels will allow astronomers to change its shape from a sphere to a paraboloid, making it easier to move the position of the telescope's focus. This will allow the south-pointing telescope to cover a broad swathe of the sky; up to 40 degrees from its zenith, compared to the 20 degree-wide strip covered by Arecibo.

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