China building world’s largest radio telescope

China is building the world's biggest radio telescope, the Five hundred metre Aperture Spherical Telescope (FAST), which is being assembled at a natural basin in Pingtang county, Guizhou Province, southwest China.

Five hundred metre Aperture Spherical Telescope / IMAGE: caltechmicrowave.org

As the name suggests, it will have a diameter of 500 metres. It will be the world's largest and most sensitive radio telescope and three times more sensitive than the Arecibo Observatory in Puerto Rico, which is so far the world's largest radio telescope.

FAST will cost 700 million yuan (around $110 million) and construction should be complete by September 2016.

The telescope will have 4,600 triangular panels and be similar in design to the Arecibo Observatory, utilising a natural hollow (karst) to provide support for the telescope dish.

Its active surface can be adjusted to create parabolas in different directions, with an effective dish size of 300 metres, capable of covering the sky within 40° from the zenith. Its working frequency will be 0.3-3.0 GHz, with a pointing precision of 4 arc seconds.

Its main reflector will correct for spherical aberration on the ground to achieve a full polarisation and a wide band supported by a secondary adjustable system with cables and servomechanisms in addition to a parallel robot to achieve a high precision.

The chief scientist of the project, Nan Rendong, from the Chinese National Astronomical Observatory (NAOC) that is part of the Chinese Academy of Sciences, said it will be commissioned in a couple of years. Original plan and construction began in 2011.

Already, NAOC constructed the Large Sky Area Multi-Object Fiber Spectroscopy Telescope (LAMOST), also known as the Guoshoujing Telescope, equipped with large FOV optics and up to 4,000 fibers on the focal plane, in Sept. 2013.

It has completed work on the 21-Centimeter Array (21CMA), which will be used to study the cosmic Epoch of Reionization, as well as on the Chinese Solar Radio Heliograph (CSRH), while work is on to build remote and better sites in Yangbajing and Ali, Tibet for new optical-infrared and submillimeter observatories.

China is also among the Five-Club building Japan's ambitious next-generation Thirty Meter Telescope (TMT) with an estimated cost of $1.47 billion (Rs14,300 crore), in collaboration with the US, Canada, Japan and India.

To be completed by 2020, TMT is a ground-based large segmented mirror reflecting telescope coming up on Mauna Kea in Hawaii and it can observe from near-ultraviolet to mid-infrared (0.31 to 28 µm wavelengths) with its adaptive optics system removing the image blur caused by the atmosphere of the Earth, reaching the potential of a large mirror.

Once built, the TMT will have by far the highest altitude, and will be the second-largest telescope after the E-ELT, both of whom use an array of small 1.44m hexagonal mirrors – a design that is different from the large mirrors of the LBT or GMT, currently in use.

In addition, there is a Square Kilometre Array (SKA) project, led by the SKA Organisation from Jodrell Bank Observatory in the UK. However, the SKA is not a single telescope, but a collection of telescopes or instruments, called an array, to be spread over long distances.

The SKA will be built in two phases: Phase 1 (called SKA1) in South Africa and Australia; Phase 2 (called SKA2) expanding into other African countries, with the Australian component also being expanded.

The project is supported by 11 member countries, including Australia, Canada, China, Germany, India, Italy, New Zealand, South Africa, Sweden, The Netherlands and the United Kingdom, and engineers and policy makers and more than 100 companies and research institutions across 20 countries cooperating in the design and development of the telescope. Construction of the SKA is set to start in 2018, with early science observations in 2020.