By Geoff Brumfiel of Nature magazine

The battle for the world's largest radio telescope has ended in a draw.

South Africa and Australia will split the Square Kilometer Array, a €1.5-billion (US$1.9-billion) project made up of 3,000 15-metre-wide dishes and an even larger number of simple antennas. The decision was announced at a meeting outside of Amsterdam in the Netherlands, following a vote by SKA's international board.

Under the terms of the deal, the split will eventually see South Africa receiving the majority of the project's 3,000 dishes, and Australia will host the low-frequency radio antennas.

"Science is the winner," says SKA board chairman John Womersley. By building on existing pilot projects in both countries, Womersley says that SKA will be made even more powerful.

Officials in Australia and South Africa responded warmly to the news. "I think it's an excellent decision," says Philip Diamond, head of astronomy and space science at Australia's Commonwealth Scientific and Industrial Research Organization. "We're really extremely delighted about this," adds Philip Mjwara, director general of science and technology at South Africa's Ministry of Science.

When completed around 2024, the telescope will be able to image the Universe at the time when the first stars and galaxies began to form. It will be 50 times more sensitive than current instruments and capable of spotting a television signal from a nearby star.

South Africa has been in a fierce competition with Australia and New Zealand over rights to host the project. In March, South Africa narrowly won out in a scientific assessment of the two sites. The results of the science panel's decision have not been made public, but low construction costs and the high altitude of the site in the remote northern reaches of the country were believed to have given it the edge. Australia and New Zealand have argued that their site in western Australia would have better infrastructure and lower insurance costs.

The split will look different over the two phases of the project. In the first phase, South Africa will see 190 dishes added to its existing MeerKAT array, according to Diamond. Australia will have 60 dishes added to its Australian SKA Pathfinder and a large number of omni-directional dipole antennas. This will give the Australian site a wide-field survey capability, whereas South Africa will be able to look deeply into a narrow part of the sky.

In phase two, the rest of the dishes will be assembled in South Africa, along with mid-frequency aperture arrays. The full complement of dipole antennas will go to Australia.

Splitting the site is politically expedient, but it will not necessarily be cheap, nor easy. Each of SKA's thousands of elements will transmit many gigabytes of data per second. That data will pass through a correlator that will assemble them into a single image, then undergo further processing. As a result, both of the remote sites will require high-speed networking and powerful supercomputers, along with roads and buildings. The redundancy could significantly raise the costs of the project.

In phase one, the cost will not rise above 10% of the originally projected €350 million, according to Womersley. Each nation has already invested around US$150 million in their respective pilot projects, and the board determined that the added capability that those projects would provide make the additional investment worthwhile. "It may be politically expedient, but it's also scientifically driven," Womersley says.

Costs for the second phase of the project seem less certain. "Because we don't have a detailed design yet for phase two it was next to impossible to estimate the costs," says Diamond. Still, he remains optimistic that additional costs can be kept low because computing and networking resources are comparatively cheap.

With the siting issue resolved, the SKA organization will have to turn its attention to financing and the final design. Rather than providing funding directly, SKA's member states are likely contribute equipment and expertise, and Diamond says that they have already contributed €90 million to the pre-construction phase.

"We've really got to get down into the detail of what we're going to build," he says.

Construction is expected to begin as soon as 2016 and first observations could be made by the end of the decade.

This article is reproduced with permission from the magazine Nature. The article was first published on May 25, 2012.