A large satellite launching to space tomorrow could become brighter than any other object in the night sky except the moon, raising concerns about its impact on astronomy.
The BlueWalker 3 satellite, built by Texas-based firm AST SpaceMobile, is set to be launched on a SpaceX Falcon 9 rocket on 10 September. The satellite is designed to test the company’s technology to beam a cellular connection, including 4G or 5G internet, directly from a satellite to mobile phones, enabling users to receive mobile coverage in remote locations.
Orbiting 500 kilometres above Earth, the 1500-kilogram satellite will deploy a huge antenna spanning 8 metres across, with a surface area of 64 square metres – about the size of a squash court. This large, flat surface will reflect a lot of sunlight, which could make the satellite extremely visible to observers on the ground.
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For astronomers, the satellites would create bright streaks across images from ground-based telescopes, potentially making them unusable for observing more distant objects.
“We are concerned,” says , an astronomer at Dark Sky Consulting in Tucson, Arizona. “It could be the brightest object in the night sky, potentially brighter than the planet Venus.”
Barentine says there are also worries about the direct-to-mobile technology of the satellite, which requires a powerful radio beam to connect with a user’s phone. That could disrupt radio astronomy, which requires very sensitive instruments to study the universe. “We’re concerned about the amount of energy in that beam,” he says. AST SpaceMobile didn’t respond to a request for comment.
While this is only a single satellite for now, AST SpaceMobile plans to launch more than 100 larger satellites called BlueBirds starting from next year. These satellites, which could be more than twice the size of BlueWalker 3, could appear even brighter in the sky. “The brighter these objects get, the more damage they will do to images of the night sky,” says Barentine.
, a space law adviser at the Secure World Foundation in the US, says that while there are no restraints under international law on the size of satellites, the launch could highlight the limitations in existing regulations. “I would really see this as an infringement on astronomers’ rights to explore space,” he says.
The Federal Communications Commission (FCC) in the US has issued an experimental licence for BlueWalker 3, but a full licence for AST SpaceMobile’s later satellites may depend on the performance and impact of BlueWalker 3. “The FCC appears willing to see how it goes and decide on a full licence later,” says Tim Farrar, a satellite communications consultant in the UK. The FCC declined a request to comment.
AST SpaceMobile is one of several companies developing new direct-to-mobile services, although it is the only one offering cellular broadband from space. SpaceX recently announced larger versions of its Starlink satellites that will enable basic cellular connections in remote locations, while Apple this week announced a partnership with satellite firm Globalstar to enable emergency messaging on iPhones via satellites.
“Most astronomers accept there will be more satellites in the future,” says Barentine. “What they want is a peaceful coexistence. We can’t make satellites invisible.”
