5G satellite briefly becomes brightest object in night sky

A recently launched 5G satellite periodically becomes the brightest object in the night sky, alarming astronomers who reckon it sometimes becomes hundreds of times brighter than the current recommendations.

Astronomers are increasingly concerned human-made space hardware can interfere with their research efforts. In March, research showed the number of Hubble images photobombed in this way nearly doubled from the 2002-2005 period to the 2018-2021 timeframe, for example.

Research in Nature this week shows that the BlueWalker 3 satellite — prototype kit designed to convey 4 and 5G phone signals — had become one of the brightest objects in the night sky and a times exceed recommended limits hundreds of times over.

The research was based on an international campaign which relied on observations from both amateur and professional observations made in Chile, the US, Mexico, New Zealand, the Netherlands and Morocco.

BlueWalker 3 has an aperture of 693 square feet (64m²) – about the size of a one-bedroom apartment – to connect to cellphones via 3GPP-standard frequencies. The size of the array creates a large surface area which reflects sunlight. Once it was fully deployed, BlueWalker 3 became as bright as Procyon and Achernar, the brightest stars in the constellations of Canis Minor and Eridanus, respectively.

The research – led by Sangeetha Nandakumar and Jeremy Tregloan-Reed, both of Chile's Universidad de Atacama, and Siegfried Eggl of the University of Illinois – also looked at the impact of the effects of Launch Vehicle Adapter (LVA), the spaceflight container which forms a black cylinder.

The study found the LVA reached an apparent visual magnitude of four times brighter than the current International Astronomical Union recommendation of magnitude 7 after it jettisoned last year.

"The expected build-out of constellations with hundreds of thousands of new, bright objects will make active satellite tracking and avoidance strategies a necessity for ground-based telescopes," the paper said.

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"Despite many efforts by the aerospace industry, policy makers, astronomers and the community at large to mitigate the impact of these satellites on ground-based astronomy, with individual examples such as the Starlink Darksat and VisorSat mitigation designs and Bragg coatings on Starlink Gen2 satellites, the trend towards the launch of increasingly larger and brighter satellites continues to grow.

"Impact assessments for satellite operators prior to launch could help ensure that the impact of their satellites on the space and Earth environments is critically evaluated. We encourage the implementation of such studies as part of launching authorization processes," the research scientists said.

Last month, Vodafone claimed to have made the world's first space-based 5G call placed using an unmodified handset with the aid of the AST SpaceMobile-operated BlueWalker 3 satellite.

Vodafone said the 5G call was made on September 8 from Maui, Hawaii, to a Vodafone engineer in Madrid, Spain, from an unmodified Samsung Galaxy S22 smartphone, using the WhatsApp voice and messaging app. ®