Artist's impression of the SKA core site, a 5 km array of radio dishes that will spread across Mileura station in Western Australia if Australia's bid is successful.

Credit: Xilostudios and ISPO

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SYDNEY: Australia and Southern Africa have made the short-list of countries vying to host the Square Kilometre Array (SKA), a giant next-generation radio telescope currently being developed by scientists in 17 countries.

The decision was made by the International SKA Steering Committee, following advice from an external
committee of seven scientists from five countries that examined the four site bids.

"This is a significant step forward in bringing to Australia potentially one of the most important international scientific projects of the 21st century," said Brian Boyle, Director of the CSIRO Australia National Telescope Facility, and leader of the Australian bid.

The SKA will be a set of thousands of radio dish antennas spread over 3,000 km, but with half of the antennas located in a central region 5 km wide. This ‘virtual' dish, thousands of kilometres in diameter, will be 50 times more sensitive than the most powerful radio telescopes currently in existence.

It will peer deep into the cosmos to pick up signs of the first stars and galaxies to form after the Big Bang; it will trace the effects of the mysterious Dark Energy that is driving the Universe apart at an ever
Increasing speed; if there are alien civilizations in our galaxy with aircraft radar, the SKA will detect them.

For Australia, the core site is proposed to be at Mileura station, about 100 km west of Meekathara and 350 km north-east of Geraldton in Western Australia. Other dishes would be distributed over the Australian continent, with the possibility of extension into New Zealand.

In Southern Africa, the central location would be at the Karoo site in the Northern Cape region of South Africa, about 95 km from Carnarvon. Further dishes would be located in South Africa itself and in neighbouring African countries - Botswana, Namibia, Mozambique, Madagasgar, Mauritius, Kenya, and Ghana.

A key requirement of the core site is that there must be a very low level of man-made radio signals in the region, since interference would mask the faint cosmic radio waves the telescope is designed to detect.

"Everything from mobile phones to television stations and even cars can cause interference and the proposed location in Western Australia is a very radio quiet area," said Gary Da Costa, President of the Astronomical Society of Australia. "However the final choice will take a range of factors into account."

Both the Australian and Southern African sites can see much of the same sky as other major ground-based optical, infrared and sub-millimetre telescopes, and both have a good view of the southern sky, which is where the centre of our Galaxy passes overhead. Both also have stable ionospheric conditions, which is important for the low-frequency observations the SKA will make.

China and the combined team of Argentina and Brazil also bid to host the SKA. Both sites were considered exceptional sites for radio astronomy, but failed to meet at least one of the broad range of exacting requirements for the Square Kilometre Array.

The proposed Chinese site would place unacceptable restrictions on placement of the central elements of the SKA, and the joint Argentinian and Brazilian proposal was eliminated because the ionospheric conditions above South America would limit the SKA's performance at low frequencies.

According to Boyle, "Hosting the SKA would further demonstrate Australia's capability in this domain [radio astronomy], as well as bring significant direct benefits through international investment in Australia."

Further analysis of the short-listed sites will now be carried out, with the final decision expected in 2008. Construction is due to begin by 2012, and will cost some A$1 billion.

What does it mean for Australia? Cosmos Online has the story.