A test satellite for a future space-to-Earth mobile phone network is brighter than 99.8 per cent of stars visible to the naked eye. If a planned fleet of 100 additional satellites is as bright or brighter, astronomers are concerned it could severely impact ground-based astronomy.
In September, Texas-based firm AST SpaceMobile launched its BlueWalker 3 satellite to test beaming a cellular connection directly to mobile phones from space.
But astronomers were concerned that the test satellite, which has a 64-square-metre reflective antenna, as well as the future satellites, called Bluebirds, could interfere with astronomy by creating light streaks on images taken from ground-based telescopes.
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In the first 64 days after the satellite launched, astronomer Anthony Mallama and his colleagues tracked its visual brightness from Earth, using binoculars to look at the test satellite and compare it to stars with a known brightness. At its most reflective times 鈥� at sunrise and sunset 鈥� they found it had an apparent magnitude of +1.5 on a scale used by astronomers in which lower numbers denote brighter objects.
鈥淭here are only 14 stars in the night sky brighter than magnitude +1.5,鈥� says of Dark Sky Consulting, a company based in Tucson, Arizona, who wasn鈥檛 involved in the work. 鈥淭hat means BlueWalker 3 under typical conditions is brighter than 99.8 per cent of all stars visible to the unaided eye.鈥�
AST SpaceMobile鈥檚 CEO Abel Avellan has suggested in public earnings calls that the proposed Bluebird satellites could be around twice as large as the Bluewalker 3, which would make them even brighter.
The Bluebirds鈥� reflectiveness at sunrise and sunset could transform the sky for casual stargazers, says at the University of San Francisco, California, and also affect cultural sky traditions that rely on stars and constellations in the sky at dawn or dusk. 鈥淭hese satellites will eventually be visible at higher altitudes above the horizon and for more of the night as they reach their planned higher final orbits,鈥� she says.
An AST SpaceMobile spokesperson said: 鈥淲e鈥檙e eager to use the newest technologies and strategies to mitigate possible impacts to astronomy. We are actively working with industry experts on the latest innovations, including next-generation anti-reflective materials.鈥�
Reference: arXiv, DOI:
