Astronomers Worldwide Troubled by New 'Cell Phone Towers in Space'

An international group of scientists is concerned by the brightness of a huge satellite, in terms of both visible light and radio waves.

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Eric Mack
3 min read
The Nicholas U. Mayall 4-meter Telescope from below, against a backdrop of a starry sky

A composite image shows trails in the night sky left by BlueWalker 3 above the Nicholas U. Mayall 4-meter Telescope at Kitt Peak National Observatory in Arizona.


A sprawling new satellite built to connect directly with mobile phones on the surface is brighter than most of the stars in the night sky, according to astronomers who are calling it a threat to their work and humanity's view of the universe.

The offending orbital object is AST SpaceMobile's Bluewalker 3, which was launched on Sept. 10, but its 64-square-meter (693-square-foot) array of solar panels and antennas was just fully unfurled earlier this month.

The International Astronomical Union coordinated observations from around the planet, which found that the satellite is almost as bright as stars such as Antares and Spica, the 15th and 16th brightest in the night sky, respectively. Another study found it to be a little less reflective, on par with the 22nd brightest star or so. 

It isn't just Bluewalker 3 that concerns astronomers, but rather the fact it serves as a test model for a constellation of over 100 so-called Bluebirds the company aims to launch as part of its plan to build a network of satellites to provide 5G connectivity from orbit to Earth -- "cell phone towers in space," as the IAU describes them. 

"BlueWalker 3 is a big shift in the constellation satellite issue and should give us all reason to pause," Piero Benvenuti, director of the IAU Center for the Protection of the Dark and Quiet Sky from Satellite Constellation Interference, said in a statement.

Astronomers have been more concerned about the potential impacts from mega-constellations of thousands of satellites like SpaceX's Starlink, but the IAU says AST SpaceMobile's plans raise new issues because of the strong radio waves they will transmit that could interfere with astronomical observations. 

Philip Diamond, who directs the the Square Kilometer Array Observatory in South Africa and Australia, worries that orbiting cell towers aren't subject to the same "quiet zone" restrictions that protect radio astronomers from interference by terrestrial cellular networks. 

"Astronomers build radio telescopes as far away as possible from human activity, looking for places on the planet where there is limited or no cell phone coverage," Diamond said in a statement. "New satellites such as BlueWalker 3 have the potential to worsen this situation and compromise our ability to do science if not properly mitigated."

The IAU notes that it has already begun conversations with AST SpaceMobile about potential mitigation measures. 

"We are actively working with industry experts on the latest innovations, including next-generation anti-reflective materials," the company said through a spokesperson.

The company adds it "is committed to avoiding broadcasts inside or adjacent to the National Radio Quiet Zone (NRQZ) in the US and additional radioastronomy locations that are not officially recognized, as required or needed. We also plan to place gateway antennas far away from the NRQZ and other radio-quiet zones that are important to astronomy."

AST SpaceMobile CEO Abel Avellan said in a statement earlier this month the goal is to build a constellation that will eliminate mobile dead zones on Earth.

"Every person should have the right to access cellular broadband, regardless of where they live or work. Our goal is to close the connectivity gaps that negatively impact billions of lives around the world."