Dual sites for the SKA radio telescope

On 25 May the Square Kilometre Array (SKA) project announced that the two contenders to host the world’s largest, most sensitive, radio telescope would share the honor. Broadly, the split will be by frequency, with South Africa and its neighbors hosting the SKA’s mid-frequency antennas, and Australia, partnering with New Zealand, covering low frequencies. The decision was reached by the project’s other member countries: Canada, China, Italy, the Netherlands, and the UK. Notably absent from the collaboration is the US, which the project hopes will join later.

In its evaluation of the two sites, the selection committee slightly favored South Africa. But the excellence of both sites, and the multimillion-dollar precursor projects that each country had in the works, “gave rise to a desire to see if we could come up with a creative approach to use both,” says John Womersley, chair of the SKA board of directors and chief executive of the Science and Technology Facilities Council, the UK funding agency for particle physics, astronomy, and large science facilities. “To our surprise, the planned way forward should deliver more science for the money, because it takes advantage of the investments already made.”

The precursor arrays to be integrated into the SKA are South Africa’s MeerKAT and the Australia SKA Pathfinder (ASKAP). In South Africa, the SKA will add 190 15-m dishes to MeerKAT’s 64 13.5-m ones, for an array sensitive to frequencies from 450 MHz to 3 GHz. In Australia, a slew of small, low-frequency (70–450 MHz) dipole antennas (see the artist’s rendering on page 26) will be installed, and 60 15-m SKA dishes will supplement ASKAP’s 36 12-m ones—which will begin scientific observations by the end of this year—to serve as a survey telescope sensitive from 700 MHz to 1.8 GHz. The first phase of the SKA is scheduled to be completed by the end of this decade.

When the second phase of the SKA is completed—slated for 2023—the baseline in southern Africa will extend beyond 3000 km, with dishes in Namibia, Botswana, Zambia, Mozambique, Kenya, Ghana, Madagascar, and Mauritius. (See PHYSICS TODAY, August 2011, page 25 .) Those approximately 3000 traditional dishes will be complemented with an undetermined number of flat 60-m antennas (see artist’s rendering on page 26). In Australia, more low-frequency antennas will be added within the 200-km baseline configuration. The SKA is intended to help answer questions about star and galaxy formation, dark energy, gravity, the role of magnetism in the cosmos, and the search for extraterrestrial life, among other things.

The cost of the project’s first phase, some 10% of the full SKA, is €350 million ($433 million). The cost of the second phase is less certain, but a running estimate is €1.5–2 billion. In terms of technology, says Womersley, “we could basically build SKA now. But we couldn’t afford what it would cost. The biggest challenges are affordability and mass production.” Still to be worked out are engineering details about antenna design, number, and configuration; data transport and computing; and the financial and in-kind contributions from member countries.

In building the SKA in stages, says Womersley, “we are trying to learn the lessons of other megaprojects and to employ best practices.” Specifically, he says, the project won’t ask governments to “put billions on the table” until the technologies are mature. “We have also been careful to work closely with the people with the checkbooks, so they are comfortable with how the project and the decision making are progressing, and to make sure we avoid some of the problems that have affected other big projects.”

It helps that in both South Africa and Australia, the SKA is a visible symbol for politics and the public. The project “is seen as an important facet for maintaining Australia’s position in world astronomy,” says Brian Boyle, SKA director for Australia. “For South Africa and our African partner countries, this represents a new era,” says Justin Jonas, SKA South Africa’s associate director of science and engineering.

The dual-site decision, Boyle and Jonas say, has one winner: Global science.