When it starts taking scientific data in 2028, the Square Kilometre Array Observatory promises to be the world’s largest and most sensitive radio telescope. But as Sarah Wild discovers, its development has been shaped by a suite of smaller experiments that are already resetting the agenda – and flagging problems that the giant telescope could face
Eyes on the skies A composite image with South Africa's MeerKAT telescope in the foreground. The backdrop shows a visible night sky on the left, with MeerKAT's radio view of the centre of the Milky Way on the right. (Courtesy: SARAO)
From its sites in South Africa and Australia, the Square Kilometre Array (SKA) Observatory last year achieved “first light” – producing its first-ever images. When its planned 197 dishes and 131,072 antennas are fully operational, the SKA will be the largest and most sensitive radio telescope in the world.
Under the umbrella of a single observatory, the telescopes at the two sites will work together to survey the cosmos. The Australian side, known as SKA-Low, will focus on low-frequencies, while South Africa’s SKA-Mid will observe middle-range frequencies. The £1bn telescopes, which are projected to begin making science observations in 2028, were built to shed light on some of the most intractable problems in astronomy, such as how galaxies form, the nature of dark matter, and whether life exists on other planets.
Three decades in the making, the SKA will stand on the shoulders of many smaller experiments and telescopes – a suite of so-called “precursors” and “pathfinders” that have trialled new technologies and shaped the instrument’s trajectory. The 15 pathfinder experiments dotted around the planet are exploring different aspects of SKA science.
Meanwhile on the SKA sites in Australia and South Africa, there are four precursor telescopes – MeerKAT and HERA in South Africa and Australian SKA Pathfinder (ASKAP) and Murchison Widefield Array (MWA) in Australia. These precursors are weathering the arid local conditions and are already broadening scientists’ understanding of the universe.
“The SKA was the big, ambitious end game that was going to take decades,” says Steven Tingay, director of the MWA based in Bentley, Australia. “Underneath that umbrella, a huge number of already fantastic things have been done with the precursors, and they’ve all been investments that have been motivated by the path to the SKA.”
Even as technology and science testbeds, “they have far surpassed what anyone reasonably expected of them”, adds Emma Chapman, a radio astronomer at the University of Nottingham, UK.
MeerKAT: glimpsing the heart of the Milky Way
In 2018, radio astronomers in South Africa were scrambling to pull together an image for the inauguration of the 64-dish MeerKAT radio telescope. MeerKAT will eventually form the heart of SKA-Mid, picking up frequencies between 350 megahertz and 15.4 gigahertz, and the researchers wanted to show what it was capable of.
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