The world’s most powerful radio telescope is taking shape in the Karoo and will soon be able to answer questions scientists and astronomers from around the world haven’t even thought of yet.
From a remote corner in the Northern Cape, together with another outlying site in Western Australia, it will soon be possible to look back nearly 14-billion years to the very beginnings of the universe using the most powerful radio telescope in the world linked to a network of supercomputers.
At a site about 80km away from the Karoo town of Carnarvon you can see deeper into the cosmos than from anywhere else on earth. It’s where the MeerKAT array of 64 interlinked dishes is located. The MeerKAT is the South Africa-developed precursor to the Square Kilometre Array (SKA), which is a R35bn astronomy endeavour involving 16 countries that observes the southern sky and picks up the faintest and farthest radio signals from the universe and turns them into data.
The project is already producing stellar work and the MeerKAT dishes will be integrated with the SKA telescope when the first phase of the operation is completed in 2028.
The telescope will seek to discover such things as why the expansion of the universe is accelerating, what the universe looked like billions of years ago when the first galaxies formed, and whether there is life elsewhere. As these questions are answered, they will lead to further interrogation — questions that haven’t yet arisen.
The SKA is made up of two huge radio-telescope arrays that are linked by fibreoptic cable and directed at the skies in the southern hemisphere, but don’t always point at the same section of the sky. Mid-frequency radio waves (similar frequencies to those received by cellphones and satellites) will be received in South Africa via 197 enormous steerable dishes when the project is completed.
The first SKA-Mid dish, as these are called, was lifted in early July. Low-frequency radio waves (similar to those received by car radios) will be collected in Western Australia by very different antennas. They’re smallish — 2m high — and shaped like Christmas trees. There will eventually be 131,000 of these in steel forests dotted around rural areas.
It’s important to differentiate between optical telescopes that, like cameras, are limited by the physical size of their lenses, and radio telescopes, which can be deployed as interconnected arrays over large areas to combine as one large radio telescope capable of producing extremely detailed images of distant astronomical sources on the far side of the universe.
Optical telescopes require dark skies to work most effectively; it’s the reason the Southern African Large Telescope is sited in the dark sky reserve near Sutherland in the Karoo, where there is no light pollution, just more than 200km southwest of the SKA.
By contrast, radio telescopes require quiet skies — regions where radio frequency interference (RFI) from things such as cellphone masts, cellphones, radios, aircraft navigational beacons and general human activity are at a minimum. The Karoo is ideal; many areas don’t even have cellphone coverage.
“Everything produces a radio signature,” says Pontsho Maruping, MD of the South African Radio Astronomy Observatory (Sarao). It is part of the National Research Foundation, which manages South Africa’s astronomy programmes and telescopes.
“Our task, using highly sophisticated and sensitive equipment, is to understand the universe. Our MeerKAT telescopes receive all the radio waves they see in the universe. These are brought back and transformed into data. The noise is filtered out and eventually we are left with the data we send to astronomers and scientists. They then analyse and interpret that data to draw out an image,” Maruping says.
There’s a long queue for telescope time and a lot to look at. There are about 200-billion stars in the Milky Way alone, and it’s just one of at least 200-billion galaxies we know of.
Sarao data centre manager Andre Walker runs the supercomputer-powered onsite data network at MeerKAT. It’s housed in a shallow bunker below ground, as is the dedicated power generation facility that charges the entire location’s dishes and servers. These are all set in their sunken position to minimise and shield the dishes from RFI.
Walker knows his numbers — he has to, because, to coin a phrase, they’re astronomical.
“When we’re fully operational we’ll be running the largest supercomputer in South Africa, which is also one of the largest in the world. Data collected here and processed on site will be sent via fibreoptic cable to the Centre for High Performance Computing in Cape Town for deeper analysis,” Walker says.
Satellite operators and governmental agencies are working out celestial paths that minimise disruptions to astronomers using powerful radio telescopes
“It’s the ultimate big data challenge, due to the volumes we’ll have to store, transport, process and distribute to users around the globe.”
An average of eight terabits per second of data will be transferred from the SKA telescopes in South Africa and Australia to central signal processors in Cape Town and Perth.
Two supercomputers will each have a processing speed of about 135 PFlops, or peta floating point operations per second (a measure of computer performance). This would place them in the top 10 of the fastest supercomputers on earth.
“We will archive over 700 petabytes of data per year — about the data storage capacity of around 1.5-million typical laptops every year by today’s standard,” says Walker.
A project the scale of the SKA is not without challenges. The MeerKAT array is close to one of the busiest airways in the world, between Joburg and Cape Town, a source of significant radio interference.
Says Adrian Tiplady, deputy MD of strategy and partnerships at Sarao: “What we try to do is optimise the use of the radio frequency spectrum. We adopt protection levels that allow us to undertake science observations across the radio frequency spectrum. Essential services such as safety of life or emergency services can exceed these levels but do so in a well-regulated and controlled manner that allows us to continue to perform observations in the rest of the band.”
Of greater concern is satellite congestion between Earth and the rest of the universe. The recent boom in satellite mega-constellations such as Starlink, involving very large numbers of satellites, poses significant challenges for professional astronomy. But satellite operators and governmental agencies are working out celestial paths that minimise disruptions to astronomers using powerful radio telescopes.
Thirty-two farms were needed to host the MeerKAT and future SKA sites near Carnarvon. This has ruffled feathers; merino sheep farmer Abe Louw grew up in the region and says one of the farms he owned that was incorporated into the SKA project was the subject of a forced sale.
“There was some negotiation on a willing buyer-willing seller basis, but it was clear that the land would be expropriated,” he says.
“We are also dealing with tax authorities about capital gains tax relief that we were told would [be granted]. It’s a negotiation that’s been going on for years.”
Maruping says the biggest financial contributions come from the three host countries — South Africa, Australia and the UK. “There are different levels of funding. China and India are also two of the bigger contributors,” she says.
The SKA is a truly international project that has gripped the interest of scientists and astronomers from around the world. Last month, for example, there were visitors from Nasa, Oxford University and the Paris Observatory.
“One day in the not too distant future,” says Tiplady, “with something like the SKA, we will be able to make a movie about the evolution of the universe as galaxies and stars were created — people will be able to see where everything comes from and how it was formed.”
US scientist Carl Sagan, who popularised astronomy with his 1980s TV series Cosmos, famously said we are made of star stuff. That star stuff is being explored and documented by the SKA, an undertaking that spans continents here on earth and extends into the farthest reaches of the universe.
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