Extract from ABC News
As an increasing number of satellites blanket Earth's orbit, a $3 billion radio telescope being built in Western Australia's outback may need to find new ways to listen for faint radio signals in the universe.
The number of satellites is expected to increase significantly in coming years and for scientists who need the ground and the space above to be quiet, satellites and their booming loud radio interference are a significant challenge.
When operational, the Square Kilometre Array (SKA) radio telescope in Western Australia's Murchison region will detect and interpret faint radio signals from space via low frequencies and allow astronomers to see the birth of stars and galaxies.
It is expected to be operational by 2030, when some experts are predicting up to100,0000 satellites will be orbiting Earth and emitting both intentional and unintentional radio noise.
Federico Di Vruno is the spectrum manager for the SKA Observatory (SKAO), the group building the two radio telescope arrays in WA (SKA-Low) and South Africa (SKA-Mid).
He said for a radio astronomer listening intently for faint radio signals, the loud radio noise from a passing satellite can be like blinding a person with a flashlight in a dark room.
"The situation is getting more difficult because of the density of satellites in Earth's orbit," Mr Di Vruno said.
"We are seeing more satellites moving in the sky and that creates more radio signals or interference."
The majority of the recent satellite launches have been for telecommunication services.
Amazon's Project Kuiper and Elon Musk's SpaceX are just two companies that are planning to launch tens of thousands of satellites over the coming years.
Listening for whispers
Dr Chris De Pree is the deputy spectrum manager for the National Radio Astronomy Observatory, which operates radio antennas across the United States.
He says the current situation is like trying to listen for whispers while the satellites are yelling with bullhorns.
Dr De Pree said the observatory could no longer use some frequencies at its Green Bank facility in West Virginia, the largest steerable radio dish in the world, due to the "noise" created by satellites.
He said interference from satellites was at the point where some scientists were scoping beyond Earth for the next ideal radio astronomy location, with the moon looming as an ideal location.
"It sounds a little crazy, but these are real discussions. This is definitely considered by the International Telecommunications Union to be an important possibility," Dr De Pree said.
"We have this opportunity to have this pristine spectrum environment on the far side of the moon that is protected from earth emissions by the moon itself.
"If you put instrumentation there, you could operate down to very low frequencies without almost any interference at all."
On Earth in the meantime, Dr De Pree said good relationships with satellite companies were essential to share the skies, but that was not always guaranteed.
"How many more companies will go to space and how many of those will cooperate, especially companies that are not in the US or Australia, that are based in foreign countries where we might not have good relations," he said.
'The horse has bolted'
Right next to where the SKA-Low is being built lays the Murchison Widefield Array (MWA) radio telescope, which has been operating since 2013.
Astrophysicist Professor Steven Tingay said the increase in interference from satellites had been noticeable in the past five years and was now impacting the quality of their observations.
"A bit of me feels that the horse has bolted and we're in catch-up mode at this point," he said.
Professor Tingay said while the Murchison region had appealed at the time of planning for SKA-Low, it might not have the same appeal now.
"Those sites were selected because they were pristine, away from humans, away from cities, away from FM radio transmitters, TV transmitters, away from electronics," he said.
"If you were choosing that site today, you'd need to take into account that there's this level of interference from space that you can't escape.
"What's the point of putting a telescope in a pristine location, which is remote, difficult to work at, expensive, when you can't escape the interference anyway."
But Professor Tingay said it was important to recognise the social good being delivered by satellites, such as fast internet for isolated and disadvantaged areas.
"There's a social good element to what the satellite operators are doing and you've got to balance that up against possible impacts to things like radio astronomy," he said.
Dealing with 'more and more' satellites
Dr David Gozzard is a physicist at the International Centre for Radio Astronomy Research at the University of Western Australia.
He said radio astronomers did their observations in internationally agreed clear bands that were reserved for science, but the problem was accidental transmissions bleeding into those wave bands.
"The onboard computers and electronics are creating enough interference that our sensitive telescopes on the ground are seeing," Dr Gozzard said.
"It gets harder and harder to remove the noise created by this proliferation of satellites as there are more and more satellites transmitting on different wavelengths.
"Astronomers have to find new ways of filtering out that noise."
The picture below shows the lines where SpaceX's Starlink satellites have passed over Australia.
Dr Gozzard said astronomers had been facing interference from satellites for some time and were always finding new ways to peer though the noise.
Telescope to last 50 years
SKA Observatory's Federico Di Vruno remains positive, saying that the life of the satellites will be to their advantage.
"We are building a telescope that will last 50 years," he said.
"The advantage is that the low orbit satellites have a short life [five years].
"They need to change or place new satellites up there, so there is an opportunity for revision for technologies to try and make satellites less noisy."
The chief operations scientist for SKA-Low, Professor Cath Trott, said the Murchison project would be able to overcome the satellite noise, and would be able to meet its goal of detecting faint noises beyond the Milky Way.
"There's still a large amount of uncertainty as to what the effects of these satellites will be," she said.
"Some of the work that has been done by some of the existing radio telescopes has been quite preliminary and by necessity they've had to extrapolate to what the impact could be and so the research [into satellite noise effects] that's underway now is really important for us to understand that.
"We have a lot of techniques to get rid of the really loud frequencies and listen to where we want to observe.
"I think we'll do great science with it."
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