SKA: World's biggest radio telescope prepares for crucial new phase

From design to "metal on the ground" - engineers and scientists behind the Square Kilometre Array are getting ready to hit the construction button, despite a scaling down on design.

When a stranger arrives in Carnarvon, a dusty one-pub town in South Africa’s semi-desert Karoo region, people tend to notice. Especially if that stranger is 25m tall and weighs 40 tonnes.

The first prototype dish of the Square Kilometre Array (SKA), which, once completed, will be the world’s biggest radio telescope, is due to appear near Carnarvon in November. Funded by 10 countries, the SKA promises to be 50 times more sensitive than any other radio telescope – and will aim to help scientists resolve some of the most perplexing questions of our time. How were the first stars and galaxies in the universe born? What is dark energy? And is there anybody else out there?

Recently, though, the ambitious multinational project has faced cutbacks, with ever-increasing costs and design considerations forcing scientists to reduce the planned number of antennas. Despite the setback, the telescope has already changed the way the world sees Africa, its scientists and engineers, says South Africa’s science and technology minister Naledi Pandor. “For the first time, global research infrastructure is being built on African soil,” she says. “Some believed South Africa would not be able to deliver, and questioned the ability of our scientists, engineers and administrators. But the fact that we have got to this point has helped turn those sceptics into positive collaborators.”

It all began in the early 1990s, when the International Union of Radio Science created the Large Telescope Working Group aimed at developing the next-generation radio observatory. After years of discussions, proposals and various agreements, two locations were selected, far away from any human activity and any interference emitted by TVs, radios, mobile phones and the like. An engineering jigsaw puzzle, with components being shipped in from five countries, the first huge prototype dish will be assembled at the heart of South Africa’s SKA site, in the sparsely populated Northern Cape province. The telescope’s second component is being built in the Outback of Western Australia, some 350km north-east of the small town of Geraldton.

A new chapter begins

Using a combination of low-frequency antennas in Australia and mid-frequency dishes in South Africa, the SKA will allow astronomers to gaze billions of years back in time, creeping ever closer to the moment the universe began. Once completed, the massive array will comprise up to an estimated 3,000 dishes and a million antennas.

For the hundreds of engineers involved, designing the SKA and all its supporting infrastructure has demanded a great deal of ingenuity. Somewhat resembling spiral galaxies, both sites will consist of dense cores and spiralling arms of antennas. “We’re getting close to construction,” says Mathieu Isidro, the SKA Organisation’s deputy communications and outreach manager. “We’re in the last stretch of the design of the telescope and are heading towards critical design reviews. We have a telescope the community is happy with and in about 18 months we plan to go to production with it.”

Apart from working on the future dishes, both host nations have also been building precursor telescopes. In South Africa, the MeerKAT array – which has already spotted hundreds of new galaxies – should be completed next March. Of its 64 dishes, 43 have already been built. Once assembled, the first SKA prototype dish will link to this array and, over the course of the first phase of construction, to 130 more dishes just like it.

The original 2013 design consisted of installing 250 dishes in Africa, but was revised over time to 197. It was further reduced to 194 at a recent SKA council meeting in the Netherlands in July, when the member states decided to trim the SKA’s budget to make it fall within a €674 million cap. At the meeting, it was decided that the dishes will, for now, be spread over 120km (as opposed to the originally proposed 150km).

In Australia, the number of antennas will be cut from 512 to 476. The ‘wingspan’ of the array will be reduced, too: the stations will now be squeezed into an area of 40km rather than 65km. As recently reported, some astronomers worry that the scaling back of the project and the potential loss of resolution caused by the shrinking of the ‘collecting bucket’ may lead to weaker signals emanating from the Big Bang not being detected. There are also concerns about the cost of reverting to the original designs should more funding become available later.

But the SKA Organisation says the changes are minimal and, with extra money, the telescope can be scaled up again. Martin Austin, the SKA Organisation’s engineering project manager, says the design has not changed significantly and what is being built is still the full telescope. Pandor agrees, saying the cost adjustment is reasonable. “I’ve been assured the design will satisfy all our requirements and the scaling down is not a scaling down in quality,” she says. “We’re committed to an excellent instrument.”

Tonnes of concrete

In Australia, the two precursor telescopes are the MWA and ASKAP – the latter expected to be fully operational before the end of the year. The country’s government has recently boosted its investment in the SKA pre-construction design by AUD7.6 million (£4.6 million) (on top of the AUD20 million already spent).

The new SKA antennas to be built in Australia, which stand 2m tall, are far smaller than the dishes to be built in South Africa, each of which supports a 15m-wide reflector, comprising more than 60 aluminium panels. But while the Australian antennas require no concrete foundations, both sites have their complexities, such as distributing power or massive amounts of data across the networks, says Austin.

“We have to engineer and construct across vast areas,” he says. “The power loads are very low and our losses are tremendous. We’re trying to pump out quite small amounts of power over very long lengths… that’s where the challenge comes in.”

To prepare the bases for the 130 dishes in the Karoo region in South Africa, engineers will be using enough concrete to fill five Olympic-sized swimming pools. In Australia, nearly a square kilometre of ground mesh will be put down for the antennas. A combined 600km of tracks and dirt roads will have to be built, says Austin. “That’s like building 100km of motorway in the UK.”

And then there is the really tricky stuff, like working in remote, radio-quiet environments and installing surveillance cameras that shouldn’t interfere with the world’s most sensitive radio telescope. “Everything produces electrical noise. As soon as there’s a switch, we’re in trouble,” says Austin.

Australian SKA project director David Luchetti says he is impressed by his country’s progress. “Over the next few months, the Australian SKA office will focus towards greater engagement with industry, as we prepare for the SKA contracts to be issued over the next few years,” Luchetti writes in his latest online update.

For Pandor, every new SKA milestone counts. Overall, more than 70% of MeerKAT has been designed and built in Africa, while a component of the new SKA dishes will be made in South Africa. And just last month, Ghana, one of South Africa’s partner countries, transformed an old satellite communications station into a fully functioning radio dish. The 32m antenna will be integrated into the African Very Long Baseline Interferometry Network, in preparation for the second-phase construction of the SKA across the continent. For Pandor, such developments show invaluable exchange of knowledge and skills.

If all goes according to plan, the SKA will hit the “construction button,” as Austin calls it, in mid-2019. At the moment, though, the SKA Organisation hopes that more countries will become members to allow more funding to eventually scale the project back up to its original size – taking those involved, Pandor says, to “a space we’ve never been before”.

Five Facts about the SKA: 

• The combined collecting area of the SKA is equivalent to 140 football pitches
• The SKA will use enough optical fibre to wrap twice around the earth
• The dishes of the SKA will produce data equal to 10 times the global internet traffic
• The data collected by the SKA in a single day would take nearly two million years to play back on an iPod
• The SKA’s central computer will have the processing power of about 100 million PCs