China building world’s largest radio telescope


China has begun construction of the world’s largest single aperture radio telescope – the Five hundred metre Aperture Spherical radio Telescope (FAST), which will be completed in five years time.

It will be able to see more than three times further into space and view the skies ten times faster than the Arecibo Observatory in Puerto Rico, which holds the title of the largest single-surface radio telescope ever built.

According to New Scientist magazine, FAST came about when China unsuccessfully entered the global Square Kilometre Array (SKA) competition for a radio telescope with a collecting area of one square kilometre.

FAST’s surface will be able to change shape to help it survey the sky, allowing it to examine objects seven billion light years away. In contrast, the Arecibo dish is fixed and focuses radio waves on a point above the dish, where they are analysed. However, this means that not all of the collecting surface is being used.

The FAST telescope overcomes this issue by allowing its 4 400 triangular aluminium panels to move, changing the dish’s shape.

The telescope is being constructed in a remote region of the Guizhou province in southern China, to avoid disruptive man-made radio interference. In March workers began construction work in an 800 metre wide depression surrounded by mountains. New Scientist reports that work should be finished by September 2016.

Meanwhile, South Africa is competing against Australia to host the Square Kilometre Array (SKA). South Africa’s chosen site is near Carnarvon in the Northern Cape, a desolate area that has few cellphone or radio towers to create interference.

The international SKA committee is expected to make its final decision as to which country will host the array in March next year. Construction work will begin in 2013 and operations will start in 2015. The winning country will earn around €200 million a year for 20 to 30 years in expenses related to operations and maintenance.

As part of the bid, SKA SA is designing and building the MeerKAT radio telescope, which is being partly funded by the Department of Science and Technology. MeerKAT will be one of the largest and most powerful radio telescopes in the world. Infrastructure for this device is being rolled out this year and should be in place by the end of next year. Infrastructure includes buildings, roads, the power supply, antenna foundations and the optical fibre network.

A MeerKAT prototype has been built at the Radio Astronomy Reserve in the Karoo. Called the MeerKAT Precursor Array (MPA), the radio telescope is in the process of being commissioned. Construction of the MPA began in August 2009 and was completed in January last year. It comprises of seven composite parabolic dishes, each with a diameter of 12 metres. At a later stage it is intended to integrate the MPA with MeerKAT, which will comprise 80 dishes. MeerKAT should be completed by December next year and commissioned in 2013 at a cost of R860 million.

Even though construction of MeerKAT is only beginning, many astronomers have applied to use the telescope. More than 43 000 hours (five years) of observation time has already been allocated to astronomers. MeerKAT will be used to hunt for gravity waves, which have never before been detected but which theoretically exist. Scientists will look for distortions gravity waves would cause to faint radio signals emitted by pulsars (dense remains of exploded supernovae).

The Square Kilometre Array was born in the early 1990s when astronomers decided they would like to be able to observe hydrogen from the birth of stars a few hundred million years after the Big Bang. They were looking for ‘neutral’ hydrogen (a single proton orbited by a single electron) which is found in the vicinity of stars that are being born. To do this would require a giant radio telescope with an area of at least one square kilometre.

South Africa became involved in the project in 2005 when it asked to become one of the countries bidding to host the telescope alongside the United States, China, Canada, Argentina and Australia. In 2009 cabinet approved a R1.6 billion budget to win the right to host the instrument. The budget includes construction of the MPA and MeerKAT. If South Africa wins the bid, other southern African countries in a 3 000 km radius will host outlying stations that connect to the main Karoo site. Namibia would host about three antenna stations; Botswana four; and one each in Mozambique, Mauritius, Madagascar, Ghana, Kenya and Zambia. Each antenna station will consist of roughly 30 to 40 antennae.