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Starlink satellites flooding sky with radiation, which could be hurting radio astronomy: study

Artist’s impression of a large satellite constellation in low Earth orbit circling above the LOFAR telescope. (Daniëlle Futselaar) Artist’s impression of a large satellite constellation in low Earth orbit circling above the LOFAR telescope. (Daniëlle Futselaar)
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Elon Musk’s thousands of Starlink satellites aren’t just disrupting scientific research by causing streaks in deep space photos — according to a new study, they are also dumping “unintended electromagnetic radiation” into space, something that could be a major problem for Earth-bound astronomers.

In the study, forthcoming in the peer-reviewed journal Astronomy & Astrophysics, scientists observed 68 Starlink satellites made by SpaceX and found that the satellites in low Earth orbit could be muddling or even drowning out signals from deeper in space that radio astronomers search for.

Some of the radiation emitting from the satellites falls within a bandwidth that is designated by the International Telecommunications Union (ITU) to allow radio astronomers to perform their work, according to the study.

“We detected radiation between 110 and 188 MHz from 47 out of the 68 satellites that were observed. This frequency range includes a protected band between 150.05 and 153 MHz specifically allocated to radio astronomy by the International Telecommunications Union (ITU)”, Cees Bassa from ASTRON, the Netherlands Institute for Radio Astronomy and co-author of the study, said in a press release.

However, because this type of radiation isn’t covered by any international regulations, SpaceX isn’t running afoul of any actual rules — even though this type of equipment is strictly regulated if it’s terrestrial to ensure no devices interfere with others.

The study comes from the International Astronomical Union’s Centre for the protection of the Dark and Quiet Sky from Satellite Constellation Interference (CPS), an organization made up of astronomers from across the globe that is dedicated to studying astronomical matters that pertain to satellites cluttering the night sky. The organization was formerly launched in 2022, but the idea came from the launch of the first 60 Starlink satellites in May 2019, which was a number that was unprecedented at the time.

Since then, Starlink has launched more than 3,000 satellites, which provide internet to more than 50 countries, including Canada. They are aiming to hit 10,000 satellites by 2027.

Previous research on satellite interference with astronomy has focused on the visual impact of a cluttered night sky, with several studies showing that satellites are leaving pale streaks on thousands of night sky photography, potentially blocking telescopes and cameras from capturing accurate observations from the ground.

But less well understood is how satellites affect radio astronomy.

“This study represents the latest effort to better understand satellite constellations’ impact on radio astronomy,” Federico Di Vruno, lead author of the study and co-director of CPS, said in the release. “Previous workshops on Dark and Quiet Skies theorised about this radiation, and our observations confirm it is measurable.”

Radio astronomy is the branch of astronomy that studies radio waves coming from deep space. Instead of relying on the visible light spectrum and photographs of space, radio astronomy uses the patterns and qualities of radio waves to organize them into signals that can tell us things about celestial objects we might not be able to see.

The reason we know about pulsars — spinning remnants of stars gone supernova that flash radio waves out at regular intervals — is because of radio astronomy. This branch also discovered something known as the Cosmic Microwave Background Radiation, which is the evidence left over from the Big Bang.

In this new study, researchers used observations from a telescope in the Netherlands called the Low Frequency Array (LOFAR) to track the radiation coming from onboard electronics on the Starlink satellites.

This radiation is different from communications transmissions facilitated by satellites, which have long been something radio astronomers have to contend with in the course of their research.

Human-made radio signals are capable of drowning out the faint signals from deep space, so many radio astronomy sites are specifically built in areas that have protections from terrestrial interference, including radio-quiet zones.

The discovery in this study that there is another confounding signal from satellites for radio astronomers to worry about — this electromagnetic radiation — is something researchers say we need to look into more.

“Our simulations show that the larger the (satellite) constellation, the more important this effect becomes as the radiation from all the satellites adds up,” Benjamin Winkel, a scientist with the Max Planck Institute for Radio Astronomy (MPIfR) in Germany and co-author of the study, said in the release.

“This makes us worried not only about the existing constellations but even more about the planned ones — and also about the absence of clear regulation that protects the radio astronomy bands from unintended radiation.”

Although this study focused on Starlink satellites due to their high saturation in the market, authors say that other low-Earth-orbiting satellites likely emit the same radiation, and that this isn’t just a SpaceX issue.

The company is aware of this new study, according to the press release, and “has offered to continue to discuss possible ways to mitigate any adverse effects on astronomy in good faith.”

The authors praised SpaceX for collaborating with astronomers, but pointed out that all satellite operators need to be part of a broader change to ensure that we can continue to study space without obstruction.

“We believe that the early recognition of this situation gives astronomy and large constellation operators an opportunity to work together on technical mitigations pro-actively, in parallel to the necessary discussions to develop suitable regulations,” Gyula Józsa, a scientists with MPIfR and co-author of the study, said in the release. 

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