SpaceX’s Starlink satellites are leaking radiation, scientists confirm

The constellations of satellites that swarm Earth’s orbital skies are currently polluting wavelength bands that should be protected for radio astronomy.

Electronics aboard SpaceX’s Starlink satellites “leak” low-frequency radio waves, separated from their allotted downlink bands, in a way that could impact our ability to perform astronomy, according to new research.

“This study represents the latest effort to better understand the impact of satellite constellations on radio astronomy,” says engineer Federico Di Vruno of the SKA Observatory and the International Astronomical Union.

“Previous Dark and Quiet Skies workshops have theorized about this radiation, our observations confirm that it is measurable.”

As Earth’s skies become more crowded, the effect satellites have on our study of space becomes increasingly worrisome. Currently, SpaceX has about 4,365 of its small internet satellites in Earth orbit, with thousands more planned. And I’m not the only company. OneWeb has over 600 of them. Amazon plans to launch thousands more starting in 2024.

SpaceX has listened to concerns about visible light pollution and has designed a new, fainter satellite. But visible wavelengths represent only one type of terrestrial astronomy. The other, probably much larger, branch is radio astronomy, and therein lies what could be a problem.

Radio frequencies between 10.7 and 12.7 gigahertz are used by satellites for downlink communications, at least in Europe; researchers have already expressed concern about those.

But scientists thought the satellites might be emitting unwanted radio waves outside that band. This is what Di Vruno and his colleagues have been trying to investigate.

They used Europe’s Low Frequency ARray (LOFAR), a network comprising some 20,000 radio masts spread across 52 locations. With this level of sensitivity they observed 68 satellites belonging to the Starlink constellation. Sure enough, they detected an electromagnetic leak.

“With LOFAR, we detected radiation between 110 and 188 MHz from 47 of the 68 satellites observed,” says astronomer Cees Bassa of ASTRON, the Dutch Institute of Radio Astronomy.

“This frequency range includes a protected band between 150.05 and 153 MHz specifically assigned to radio astronomy by the International Telecommunication Union.”

This emission appears to be unintentional, coming from the electronics of the satellites. It also doesn’t break any rules. Here on Earth, the International Electrotechnical Commission places strict restrictions on electrical devices to control electromagnetic interference, but those rules don’t apply in space.

The effect is relatively small, so far. But that won’t necessarily always be the case. The more satellites up there that emit this unintentional radio signal, the brighter it will get.

There is, however, a fix already in the works. The researchers contacted SpaceX, which is working on ways to reduce or remove this unintentional leak. And while there are already thousands of cars up there, we’re really only at the beginning of satellite constellation technology.

This makes satellite radio leakage a problem that was identified relatively early. Future projects can be adapted accordingly as regulators work to fill the unexpected gap in the official rules.

“The present study highlights one example of the various channels of how technological development can have unforeseen side effects on astronomy,” says astronomer Michael Kramer of the Max Planck Institute for Radio Astronomy and the Astronomische Gesellschaft in Germany.

“With SpaceX leading the way, we now hope for broad support from the entire satellite industry and regulators.”

The research was published in Astronomy and astrophysics.