Satellite megaconstellations' radio leakage threatens to blind ground-based astronomy within 30 years

On a clear night, if you watch the sky shortly after SpaceX launches a batch of Starlink satellites, you might see a bright string of lights streaking across the heavens—a phenomenon known as a Starlink train, caused by sunlight reflecting off the newly deployed spacecraft before they spread out into the wider network. It's a visible reminder that private satellite megaconstellations are becoming reality. But there's something else up there, invisible to the human eye, that poses a far more serious threat to how we study the cosmos: radio waves leaking uncontrollably from these same satellites.

Radio astronomy has given us access to cosmic phenomena we cannot see any other way. Through radio frequencies, scientists detect jets of energy erupting from supermassive black holes, track the trajectories of near-Earth asteroids, and observe fast radio bursts—millisecond pulses of ultra-energetic radiation from neutron stars and other exotic objects. Radio telescopes have peered back to the Age of Reionization, roughly 400 million years after the Big Bang, when the first stars and galaxies emerged from primordial hydrogen. The Search for Extraterrestrial Intelligence relies on radio waves because any advanced civilization would likely use these same wavelengths for communication. Radio observations also help us pinpoint our precise location relative to other cosmic objects. The radio spectrum spans from roughly 3 kilohertz to over 300 gigahertz, though most astronomers focus their searches between 1 megahertz and 100 gigahertz. The world's largest single radio telescope, China's Five-hundred-meter Aperture Spherical Radio Telescope, operates between 70 megahertz and 3 gigahertz. The Square Kilometre Array Observatory, the world's largest array of radio telescopes scattered across Australia and South Africa, scans between 50 megahertz and 14 gigahertz. Increasingly, many of these frequencies are being bombarded by noise from Starlink and other satellites.

The problem is not primarily the intentional radio signals beamed down to operators on Earth—it's the unintended electromagnetic radiation, or UEMR, that leaks constantly from the spacecraft themselves. "This was not a problem before, when the number of satellites was low," Federico Di Vruno, a radio astronomer at the Square Kilometre Array Observatory and co-director of the International Astronomical Union's Centre for the Protection of the Dark and Quiet Sky from Satellite Constellation Interference, told researchers. "But now the situation has changed." When Di Vruno and colleagues used Europe's Low-Frequency Array, or LOFAR, to observe a group of first-generation Starlink satellites, they found the spacecraft were leaking UEMR at much higher rates than other orbiting spacecraft. The radiation had frequencies between 110 and 188 megahertz, overlapping significantly with LOFAR's operating range of 10 to 240 megahertz. Benjamin Winkel, a radio astronomer at the Max Planck Institute of Radio Astronomy in Germany and a co-author of that study, said the team was not surprised to detect something, but "we didn't anticipate that the level would be so high." What came next was even more shocking. In September 2024, a follow-up LOFAR study showed that newer Generation 2 Starlink satellites were leaking over 30 times more UEMR than their predecessors—this despite researchers having previously warned SpaceX about the initial findings. The radiation was emitted in roughly the same frequency bandwidth as the earlier generation.

The intensity of this radiation is staggering. The UEMR from Generation 2 Starlink satellites is up to 10 million times brighter than the faintest radio-visible objects in the night sky, which include ancient galaxies billions of light-years away. Cees Bassa, an astronomer at the Netherlands Institute for Radio Astronomy and lead author of the 2024 study, compared the difference to the faintest stars visible to the naked eye versus the brightness of a full moon. Winkel offered another analogy: trying to detect signals from beyond one of these satellites is "like taking a photograph while someone points a flashlight in your direction." Some radio telescopes will be hit harder than others depending on the frequencies they specialize in, but all will be affected in different ways. Studies requiring long-term datasets are particularly vulnerable because there is a greater chance that leaky satellites will pass overhead during data collection. Even tiny interference signals can have statistical impacts on results that researchers may not even recognize.

Starlink is not the only source of concern. Amazon's Project Kuiper, Eutelsat's OneWeb network, the European Union's IRIS² network, AST SpaceMobile's giant communication satellites, and China's Qianfan constellation are all launching competing megaconstellations. As of May 2025, there are 11,700 active satellites orbiting Earth, with more than 7,300—over 60 percent—being Starlink satellites, all launched since 2019. But this is merely the beginning. Well over 1 million satellites have been proposed globally, and many experts agree we could eventually have up to 100,000 private satellites in low Earth orbit, potentially by as early as 2050. This would likely represent the maximum number that can be sustained without satellites colliding with one another.

If that maximum is reached, there is what Di Vruno calls a "real possibility" of reaching an inflection point beyond which ground-based radio astronomy would become effectively impossible. Some radio frequencies will remain unaffected, but the obscured wavelengths will likely be lost for good, and the unaffected frequencies are unlikely to yield as many meaningful discoveries. We would no longer be able to "observe faint signals far out into the universe," which would be "a serious problem," according to Fionagh Thomson, a research fellow at Durham University who specializes in space ethics. Winkel put it more starkly: "It will eventually reach a point where it is not worthwhile to operate a radio telescope anymore." At the rate megaconstellations are growing, this could happen within the next 30 years. Some radio astronomy could still be achieved from space on a smaller scale—there are plans to build a radio telescope on the moon—but this would be extremely expensive and would capture far less data than the current suite of Earth-based telescopes.

Satellite operators can take steps to limit the damage. Most intentional downlink frequencies are kept separate from those used by radio astronomers. Some companies, including SpaceX, are investigating "boresight avoidance," in which satellites temporarily halt signal sending as they pass over radio quiet zones where telescopes are actively collecting data. But once satellites are deployed in space, there is almost nothing operators can do to limit UEMR. The problem must be addressed before launch. We know this is possible because spacecraft from NASA and other space agencies produce much less accidental radiation than private satellites do. Astronomers can also try to remove interfering signals from their datasets, but this "cleaning" may cause them to miss crucial data masked by the interference, and the effort becomes exponentially more expensive as interference increases.

The most effective solution, experts say, is to impose strict limits on UEMR through regulation. The International Telecommunication Union, a United Nations agency, currently protects specific radio frequencies on behalf of astronomers, but these regulations apply only to Earth-based sources of radio pollution, not to private spacecraft. Most satellite operators try to respect the ITU's guidelines for intentional downlinks with limited success, but UEMR frequently overlaps with protected wavelengths and remains perfectly legal. Some experts argue the ITU's radio-quiet frequency bands are no longer wide enough for modern radio astronomy. The IAU's Centre for the Protection of the Dark and Quiet Sky is hoping to have strict new regulations in place by the end of the decade and expects a breakthrough at the next World Radiocommunication Conference in 2027. But even stricter guidelines might not be enough if organizations don't respect them. "There is an assumption that imposing laws will fix complex problems," Thomson cautioned. "But not all viable solutions involve implementing binding legislation." If satellite operators care about UEMR, Di Vruno said, "we will be OK. It will be more difficult to conduct radio astronomy than it is now, but we understand technology evolves and we will evolve with it." The question is whether they will.