Sky scandal: Starlink satellites violate the rights of radio astronomers to a quiet sky
Scientists have found that SpaceX’s Starlink satellites emit radio waves in a protected band dedicated to radio astronomy and have called for regulation of the phenomenon.
Satellites launched into space to provide access to the Internet are preventing radio astronomers from studying space. Electronics aboard SpaceX’s Starlink satellites emit radio waves outside of their assigned frequency bands, scientists have found, which can disrupt radio telescopes.
“This study is the latest attempt 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.
Satellite pollution is becoming an increasingly acute problem. SpaceX currently has about 4,365 of its small Internet satellites in Earth orbit, with several thousand more planned. And it’s not the only company. OneWeb has over 600. Amazon plans to launch thousands of satellites from 2024.
SpaceX has heeded concerns about light pollution and developed a new, dimmer satellite. But visible wavelengths are only one kind of ground-based astronomy. Another, perhaps much larger, branch is radio astronomy, and this can be a problem.
Radio frequencies between 10.7 and 12.7 gigahertz are used by satellites to communicate with Earth, at least in Europe; scientists have already expressed their concern about this.
But scientists suspected that the satellites could emit unintentional radio waves outside of that range. This is what Di Vruno and his colleagues tried to explore.
They used the European Low Frequency Array (LOFAR), a network of about 20,000 radio antennas distributed over 52 locations. With this level of sensitivity, they observed 68 satellites belonging to Starlink. Indeed, they found electromagnetic leaks.
“Using LOFAR, we detected radiation between 110 and 188 MHz from 47 of the 68 observed satellites,” says astronomer Sis Bass from the Netherlands Institute for Radio Astronomy ASTRON.
“This frequency range includes the protected band between 150.05 and 153 MHz, specially allocated for radio astronomy by the International Telecommunication Union.”
This radiation 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 sets strict limits for electrical devices to control electromagnetic interference, but those rules don’t apply in space.
The effect is still relatively small. But that won’t always be the case. The more satellites out there emitting this unintentional radio signal, the brighter it gets.
However, there is a solution that is already under development. The researchers contacted SpaceX, which is working on ways to reduce or eliminate this unintentional leak.
Satellite radio emission is a problem that was discovered relatively early. Future designs may be subject to adjustments as regulators work to fill an unexpected gap in the official rules.
“The present study provides an example of how advances in technology can have unforeseen side effects on astronomy,” says astronomer Michael Cramer of the Max-Planck-Institute for Radio Astronomy and the Astronomical Society in Germany.
“SpaceX has set the example, and we now look forward to broad support from the entire satellite industry and regulators.”
The study was published in the journal Astronomy & Astrophysics.