Artist’s impression of a large satellite constellation in low Earth orbit circling above the LOFAR telescope. (Image dated July 5, 2023).
Author – Daniëlle Futselaar
Credit – International Astronomical Union (IAU), under the identifier ann23025a. CC SA 4.0.
Starlink satellites swarming Earth’s orbital skies are polluting wavelength bands that are supposed to be protected for radio astronomy.
A new study has found that the electronics on board SpaceX’s Starlink satellites are ‘leaking’ low-frequency radio waves, separate from their allocated downlink bands, something that could be a major problem for Earth-bound astronomers.
CTV News Canada is reporting that 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.
“This study represents the latest effort to better understand satellite constellations’ impact on radio astronomy,” says engineer Federico Di Vruno of the SKA Observatory and the International Astronomical Union.
“Previous workshops on Dark and Quiet Skies theorized about this radiation, our observations confirm it is measurable.”
“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.
A growing problem
According to ScienceAlert, SpaceX currently has an estimated 4,365 of their small internet satellites in Earth orbit and is aiming to hit 10,000 satellites by 2027. And they’re not the only company. OneWeb has over 600. Amazon plans to launch thousands more starting in 2024.
In January 2020, Elon Musk listened to concerns over the glare from the StarLink satellites interfering with scientists’ ability to observe the night sky and designed a new, dimmer satellite.
CTV News points out that because this particular 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.
But visible wavelengths only represent one kind of Earth-based astronomy. The other, arguably much bigger branch is radio astronomy, and herein lies what might be a problem.
The radio frequencies between 10.7 and 12.7 gigahertz are used by the satellites for communication downlink, at least in Europe. But scientists thought the satellites might be giving off unintended radio waves outside that band. This is what Di Vruno and his colleagues sought to investigate.
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.
“With LOFAR, we detected radiation between 110 and 188 MHz from 47 out of the 68 satellites that were observed,” says astronomer Cees Bassa of ASTRON, the Netherlands Institute for Radio Astronomy.
“This frequency range includes a protected band between 150.05 and 153 MHz specifically allocated to radio astronomy by the International Telecommunications Union.”
The effect is relatively small, so far. But it won’t necessarily always be that way. The more satellites up there emitting this unintentional radio signal, the brighter it will become.
“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.”
SpaceX 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.”