Starlink satellites’ leaky radio waves obscure the cosmos

While SpaceX’s Starlink satellites are enabling internet access and cell phone communications around the globe, they’re also posing a threat to radio astronomy, a new study suggests.

In some wavelength bands, unintended leakage of electromagnetic radiation from the latest generation of the satellites is more than 30 times brighter than emissions from previous versions, Cees Bassa, a radio astronomer at the Netherlands Institute for Radio Astronomy in Dwingeloo and his colleagues report September 18 in Astronomy & Astrophysics. Because the latest generation of Starlink satellites will orbit as many as 100 kilometers lower than earlier satellites, they’ll seem even brighter to ground-based telescopes. Overall, their brightness could easily mask observations of dimmer objects like distant galaxies or stars.

Radio telescopes, rather than gathering visible light, collect lower-energy waves from sources that emit radiation at longer wavelengths. Bassa and his team used six radio telescopes at an observatory near Exloo, Netherlands, to characterize the emissions from Starlink satellites during two hourlong sessions in July. Although the satellites passed through the telescopes’ field of view for between only 12 and 40 seconds, they were very bright: Compared with the faintest astronomical sources that can be observed by those telescopes, Starlink satellites are about 10 million times brighter, Bassa and his team noted.

And the problem will likely get worse: SpaceX is launching about 40 second-generation Starlink satellites each week, the researchers note, with more than 6,000 already out there (SN: 3/3/23). Bassa and his colleagues have found that other companies’ satellites are detectable by radio telescopes too, and they’re working to measure those emissions as well.

Bassa and his colleagues hope that their continuing observations will spur the developers of such satellites to redesign their equipment where possible to reduce unintended radio emissions.