Under the vast star-laden Karoo sky, on the site of what will be the world’s most powerful radio telescope, a smartphone is not permitted — even if it’s switched off.
And now the team behind the Square Kilometre Array (SKA), set for completion in mid-2028, has raised the alarm over the effect of satellite internet services on its work. Low-orbit roving satellites with sound emissions are likely to disrupt the sensitive work of mapping the universe through radio signals.
“The recent development in [non-geostationary orbit] services represent a clear and present risk to the future of terrestrial radio astronomy,” the South African Radio Astronomy Observatory (Sarao) says in its August 2024 submission to the Independent Communications Authority of South Africa (Icasa).
Much of the recent focus in the sector has been on communications minister Solly Malatsi’s policy directive on broad-based BEE and the possible role of Elon Musk’s Starlink, but Icasa’s consultation process regarding a licensing framework for the sector resulted in 48 submissions.
The SKA project is a collaboration among 15 countries, with an estimated cost of construction of R20bn. However, the scientific and economic spin-offs of the project are far greater, and have already been felt in the region.
Sarao has recommended that Icasa put in place licence conditions that protect the SKA. It wants companies to sign a co-ordination agreement with Sarao detailing measures to prevent interference with its radio telescope.
The MeerKAT telescope array, the precursor of the SKA, has already made groundbreaking discoveries that will form the basis of astronomical research for decades to come. The SKA is expected to take the work of MeerKAT to the next level.
Federico di Vruno, spectrum manager at Sarao, tells the FM that the submission to Icasa details the organisation’s deep concern about the potential impact of low-orbit satellites on the SKA.
“We care a lot about interference. That’s very strictly regulated. So, just to give you an idea, whenever we go to the SKA site in either South Africa or Australia, we cannot bring our cellphones — even if they are switched off. We cannot bring Bluetooth devices or smartwatches. There are a lot of controls for that.”
We went to great lengths to build this very special observatory ... in a very special place
— Federico di Vruno
It’s easy to regulate activities on the ground, but when the technology involved is in space, it becomes more difficult.
Di Vruno explains the subtleties. He likens the radio spectrum to a pie, broken up into pieces or slices, and regulated so that the frequency bands are used by different users, such as cellphone companies, satellites or radio astronomers.
“The radio astronomy bands are very important, because they’re in very specific frequencies that we need to use. This is because of celestial phenomena driven by physics. Radio astronomy has evolved so much in technique that we now require more bands and much more width for our observations — in other words, more of the pie.
“The benefit of doing radio astronomy is that we are a passive user of the spectrum, so we only listen, we don’t produce signals. We’re listening to the stars, if you like.”
This is the reason radio astronomy sites are in remote places such as the Karoo, where it is easier to maintain radio “quiet zones”. This is regulated at a national level; satellites, on the other hand, are regulated internationally.
“Satellites go around the Earth using a particular frequency, and as long as they stay in their lane — the ‘piece of the pie’ that was defined at international level — they are technically not doing anything wrong,” says Di Vruno.
The SKA telescopes are so sensitive they can even detect radio noise from the electronic components of satellites.
This is where Sarao comes in. Even if satellites “stay in their lane”, they could still adversely affect the telescope, he says. “We went to great lengths to build this very special observatory [the SKA] in a very special place. But there are satellite emissions from space in frequencies that we want to use to observe. So that’s where the tricky conversation comes in.”
Conversations have begun with Starlink and its Chinese equivalent, SpaceSail, which also has an interest in entering the South African market. Sarao is working closely with Icasa to protect the integrity of its work.
The SKA proponents are not advocating a ban on satellite services, but calling for balance and responsibility from the regulator and the companies entering the space.
“It’s really a discussion about how these companies might use technology to mitigate the effect on the site, and about what we can do to use more software or different capabilities.” The SKA telescopes are so sensitive they can even detect radio noise from the electronic components of satellites.
It is likely to be a tricky balance. It’s possible that the satellites would be “turned off” for brief periods when they are intersecting with the “pieces of the pie” used by the telescopes.
South Africa and the world are in uncharted territory here, aiming to strike a balance between crucial existing technologies and scientific advances of the unique magnitude the SKA can provide.
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