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Rapidly growing swarms of satellites around Earth are no longer just a nuisance for ground-based observatories — the reflections they cause are now intruding on space-based telescopes as well, according to new research.

Roughly 15,000 satellites currently circle the planet in vast internet-providing fleets, more than half of them belonging to SpaceX's Starlink network, which has more than 9,000 spacecraft in orbit. In 2023, astronomers reported that some of these satellites were already photobombing images captured by the Hubble Space Telescope, as sunlight glinted off their surfaces leaving bright trails that erase, obscure or mimic genuine cosmic signals.

If every constellation currently filed with regulators were approved and launched, Earth will be encircled by half a million satellites by the end of the 2030s.

"The natural question that comes up is: how many more space telescopes will be affected when all these constellations are launched?" study co-author Alejandro Borlaff, an astrophysicist at NASA's Ames Research Center in California, told Space.com. "This work is the first careful quantification of a potential problem."

Borlaff and his team modeled how future satellite megaconstellations would appear to four space telescopes: Two already operating ones — Hubble and NASA's SPHEREx (short for Spectro-Photometer for the History of the Universe, Epoch of Reionization and Ices Explorer), launched in March — and two planned observatories, China's Xuntian telescope, scheduled for a 2026 liftoff, and the European Space Agency's ARRAKIHS mission, expected to launch next decade.

Using orbital data for every registered constellation from the Planet4589 database maintained by astronomer Jonathan McDowell, the researchers simulated roughly 18 months of telescope operations under varying scenarios that ranged from 100 satellites to one million.

If the 560,000 satellites currently planned are deployed, the team found that one in every three Hubble images would contain at least one satellite trail. For SPHEREx, ARRAKIHS, and Xuntian, more than 96% of exposures would be affected. At the million-satellite level, roughly the number of proposals currently pending, contamination rates roughly double, the study reports.

These findings are "truly frightening," Patrick Seitzer, an astronomer at the University of Michigan in Ann Arbor who was not involved in the new study, told Nature. "This is a very important study for the future of space-based astronomy."

Until 2019, the largest commercial constellation, Iridium, operated just 75 satellites in low Earth orbit. Since then, a dramatic reduction in launch costs and the rise of rideshare missions have driven an exponential surge in deployment. The arrival of super-heavy rockets such as SpaceX's Starship, Blue Origin's New Glenn and China's Long March 9 is likely to make large-scale launches even easier, the study notes.

Crucially, image processing cannot fully recover the science lost to satellite contamination, the researchers emphasize. Techniques such as masking can hide a streak, but the cosmic signal underneath cannot be reconstructed.

"That part of the image will be forever lost," Borlaff told Space.com. Photon noise from reflected sunlight wipes out the original data, and no software, AI included, can reconstruct that data, he said, "simply because the information that came from space to the telescope detector is no longer there."

Not everyone agrees with every aspect of the team's modeling. Rafael Guzmán, consortium lead for ARRAKIHS, told Science that while his group shares the serious concern most astronomers have regarding the effects of megaconstellations, the study assumes ARRAKIHS will survey the entire sky, when it will mostly point away from Earth, where satellites are least visible. His team similarly concludes that around 96% of images would bear satellite trails, but a smaller portion of each image would be contaminated, according to the Science story.

One mitigation strategy proposed in the study is placing large satellite constellations below the altitude of space telescopes, where spacecraft spend more time in Earth's shadow and therefore appear dimmer. But Borlaff acknowledges this could increase satellites in lower orbits burn up more frequently due to atmospheric drag, and recent research suggests that materials released during reentry may harm the ozone layer. Lower orbits also make satellites appear brighter to ground-based observatories, potentially shifting the problem rather than solving it.

"This should be discussed from a multi-disciplinary perspective, not just from astronomy," said Borlaff. "We need to carefully evaluate the resources that we have so we can maintain an orbital environment that is useful for both science and industry."

The study notes that efforts to measure the environmental and scientific impacts of megaconstellations are already struggling to keep pace with launch activity, a dynamic reminiscent of the early days of ozone-layer research, when scientists' warnings about chlorofluorocarbons raced against industrial expansion until the historic Montreal Protocol imposed global limits.

When asked whether he is optimistic that meaningful mitigation is possible, Borlaff described himself as an "optimistic pessimist."

"Our results show what will happen if no action is taken, but I am positive that won't be the case," he said.