Artist impression of an outlying cluster of SKA-Low antenna stations next to a track.

An artist’s impression of SKA-Low antenna arrays.Credit: DISR

After 30 years of planning and negotiations, construction begins this week on the Square Kilometre Array (SKA), the world’s largest radio-astronomy observatory. The giant instrument — to be built across sprawling sites in Australia and Africa — will collect the radio signals emitted by celestial objects and will hopefully shed light on some of the most enigmatic problems in astronomy, such as the nature of dark matter and how galaxies form.

On Monday, astronomers and local communities will travel to the remote sites in South Africa’s Northern Cape and Western Australia to celebrate the milestone with officials from the SKA Observatory (SKAO), the intergovernmental organization in charge of the telescopes.

“We’re basically setting the foundation of this instrument for the next 50 years,” says Lindsay Magnus, the director of the telescope being built in South Africa, who is based in Cape Town, South Africa. “That’s the exciting part — this is a long-term legacy.”

Years in the making

In 2012, it was decided that what had initially been conceived as a single giant telescope would consist of two instruments, one in South Africa and one in Australia. The large distances between antennas, and their sheer number, mean that the telescopes — called SKA-Mid and SKA-Low respectively — will pick up radio signals with unprecedented sensitivity. SKA-Low will detect frequencies between 50 megahertz and 350 megahertz and SKA-Mid will pick up frequencies between 350 megahertz and 15.4 gigahertz. Both are interferometers, in which many dish-shaped antennas together act as a single telescope.

The SKA will be built in stages, and the €1.3-billion (US$1.4-billion) first phase is expected to be completed in 2028. Another €700 million has been earmarked for operation costs for the telescopes over the next decade. The ultimate goal is to have thousands of dishes in South Africa and African partner countries, and one million antennas in Australia, with a total collecting area of one square kilometre. Phase one is about one-tenth of the total planned project.

SKA-Low

The SKA-Low telescope, in Australia, will comprise about 131,000 antennas, each resembling a 2-metre-tall wire Christmas tree. More than 500 arrays of 256 antennas will dot the red sands of the site, which has been renamed the Inyarrimanha Ilgari Bundara, the CSIRO Murchison Radio-astronomy Observatory. ‘Inyarrimanha Ilgari Bundara’, a name selected by the traditional owners of the land, the Wajarri Yamaji, means ‘Sharing sky and stars’.

Earlier this month, the Wajarri Yamaji and the Australian government registered a land-use agreement that would allow the telescope to be built on Wajarri Yamaji land. Local people will act as heritage monitors and accompany SKAO officials before any ground disturbance throughout construction, says Des Mongoo, a Wajarri Yamatji community member who is looking forward to work beginning. “Once they’ve started construction, there are opportunities for Wajarri people to be involved in employment and commercial opportunities.”

Scientists are also eager for the antennas to start collecting data. SKA-Low’s “sensitivity will allow us to observe the distant Universe in much more detail than anything we’ve done so far”, says Douglas Bock, director of space and astronomy at the Commonwealth Scientific and Industrial Research Organisation (CSIRO) in Sydney, Australia. “This is particularly exciting because we know so little about the first billion years of the Universe.”

But the most exciting science will be phenomena that “we didn’t even know existed” when the telescopes were designed, predicts SKA-Low telescope director Sarah Pearce, based in Perth. The first four arrays will be collecting data by 2024, with all the arrays completed by 2028.

South Africa’s dishes

On Monday, preparations will also begin for building the first giant SKA-Mid dishes. These will form a collection of 197 antennas, extending over about 150 kilometres in South Africa’s dry Karoo region. Four will be complete in 2024, and many more will be added by 2028.

South Africa’s 64-dish MeerKAT telescope already exists on the site, and will be incorporated into SKA-Mid. In early 2022, using MeerKAT data, an international team published the most detailed image yet of the centre of our Galaxy1, the Milky Way, as well as images of mysterious radio threads2 emanating from the Galaxy’s central black hole. The South African government and Germany’s Max Planck Society are adding another 20 dishes to the telescope, as part of an extension project. MeerKAT will be incorporated into SKA-Mid only towards the end of its construction, in 2027.

“SKA will be a great scientific step forward,” says Erwin de Blok, an astronomer at the Netherlands Institute of Radio Astronomy in Dwingeloo and a principal investigator on MeetKAT’s MHONGOOSE large-survey programme looking at galaxy formation. SKA-Mid “will help us study nearby galaxies in great detail and directly detect the flow of gas into galaxies and the processes that lead to star formation”.

However, SKA-Mid’s construction will interfere with MeerKAT observations, says South African Radio Astronomy Observatory director Pontsho Maruping in Cape Town. Radio telescopes are particularly sensitive to the radio waves emitted by vehicles and communications devices. “We’re going to do everything we can to make sure that observations don’t get unduly interrupted,” she says. MeerKAT will continue observing until it is incorporated into SKA-Mid in 2027.

By the end of the year, the SKAO, based in the United Kingdom, will have awarded €500 million in construction tenders. About 70% of contracts have to go to industry in member countries. There are currently eight full members in the organization — Australia, China, Italy, the Netherlands, Portugal, South Africa, Switzerland and the United Kingdom — with France planning to join.