SpaceX and AST SpaceMobile are working to bring satellite connectivity to smartphones, but scientists say the technology risks disrupting radio astronomy. “The proposed direct-to-cell satellites would effectively eliminate the existence of radio quiet zones, greatly reducing the effectiveness of existing radio telescopes,” says Catherine Lovekin, Associate Professor of Physics at Mount Allison University in Canada. Lovekin is among the scientists and groups urging the FCC to regulate cellular satellites from interfering with radio astronomy equipment. The satellites effectively act as cell towers in low-Earth orbit, routing radio signals and internet data to phones on the ground. SpaceX and AST SpaceMobile plan to operate hundreds of direct-to-cell satellites to help carriers such as T-Mobile and AT&T serve users in dead zones. But a growing number of astronomers and scientists say the constant radio interference from so many satellites poses an “existential threat” to radio astronomy.
BlueWalker satellite (Credit: AST SpaceMobile)
In its letter to the FCC, the American Astronomical Society says scientists have made important discoveries through radio astronomy precisely because they had “clear access to the broad radio spectrum, whether through the establishment of a radio quiet zone or the placement of observatories in remote locations.”This will no longer be possible with persistent interference from overhead satellite transmissions. Without access across the broader spectrum, astronomical research will only be possible to carry out in the small sliver of spectrum allocated specifically for this purpose, greatly limiting the discovery potential,” warned the society, which has over 7,700 members. Astronomers are speaking up after the FCC in March approved new rules that allow satellite providers to beam connectivity to consumer phones. But in doing so, the commission said it was also well aware of interference concerns, including radio astronomy. That’s because a month earlier, the National Science Foundation, an independent federal agency, issued a white paper dedicated to studying the matter. “NSF’s preliminary analysis indicates significant impacts to radio astronomy systems,” the white paper noted, citing the “power levels and ubiquitous visibility in the sky” from such satellite systems. The document also warns that radio signals from the satellites “may even damage radio astronomy hardware” if a satellite’s transmitter directly passes in front of a radio astronomy receiver. “While it is possible that the severity of the harm to radio astronomy may be mitigated with careful coordination and selection of the absolute minimum bandwidths and power levels necessary for any permitted SCS, radio astronomy will be negatively impacted in any implementation scenario,” the NSF went on to say.
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SpaceX and AST SpaceMobile didn’t immediately respond to a request for comment, although both say they’ve been working with the astronomy community on mitigations to prevent interference with scientific research. Still, a key question is whether cellular satellite technology can coexist with radio astronomy or if one must come at the expense of the other. In the meantime, the scientists lobbying the FCC are urging it to require companies like SpaceX and AST SpaceMobile to prove their technologies won’t cause interference with radio astronomy before receiving commercial approval. This includes demonstrating “their ability to operate without directly illuminating, or incapacitating, or damaging the receivers at, radio astronomy observatories,” the National Radio Astronomy Observatory said in its own filing.It’s not the first time astronomers have voiced concerns about large satellite constellations. In recent years, they’ve also criticized satellites from SpaceX and AST SpaceMobile for photo-bombing their observations or emitting too much light in the night sky.So far, the FCC hasn’t cleared SpaceX or AST SpaceMobile to operate their cellular satellite systems commercially. Scientists and astronomy groups are lobbying the FCC after it opened a public comment period on its new rules for cellular satellite coverage, which also seek to minimize interference risks.
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