Since its launch in September, the BlueWalker 3 satellite has had anxious observers watching the skies in anticipation of its full deployment. Now, the prototype satellite has fully stretched out its massive array of antennas, significantly increasing its brightness and posing a threat to astronomers’ views of the cosmos.
On Monday, AST SpaceMobile announced the complete deployment of the communication array of its test satellite, unfurling its 64-square-metre antenna array in low Earth orbit. The array of antennas is the largest-ever commercial communications array deployed in low Earth orbit, designed to beam down connectivity directly to people’s phones.
The Texas-based company has been bragging about the size of its satellite, with Chairman and CEO of AST SpaceMobile Abel Avellan boasting on Twitter, “Made in TX — size matters!” when referring to BlueWalker 3. But for astronomers gathering data from the skies, it’s nothing to brag about. With its antenna fully unfurled, the satellite may be among the brightest objects in the night sky, according to Sky and Telescope.
Marco Langbroek, an astrodynamics lecturer at Delft Technical University in the Netherlands, has been tracking BlueWalker 3 since its launch. During overhead observations in September, the satellite had a brightness magnitude of around +3.5, making it visible to the naked eye but not very bright. However, since the satellite deployed its antenna array, it has become significantly brighter.
“Several early reports by other observers from the past few days indicate a significant brightening by about 2 magnitudes,” Langbroek told Gizmodo in an email. “That is about 6 times brighter than before as one magnitude difference equals a factor 2.512 in brightness.”
“One report during a very favourable zenith pass indicated a peak brightness at magnitude +2 to +1, that is about as bright as the stars of Orion,” he added. Langbroek anticipates that the satellite could get even brighter since it only started to unfold recently, and the visibility in the northern hemisphere at the moment is not ideal for astronomers to observe the satellite’s brightness.
Astronomers have expressed concerns that the satellite could interfere with observations, appearing as a bright streak of light across telescope images and saturating detectors at observatories.
NSF’s NOIRLab and the International Astronomical Union’s (IAU) Centre for the Protection of the Dark and Quiet Sky from Satellite Constellation Interference have called on astronomers from around the world to observe the satellite and note its brightness magnitude as it orbits Earth. “[Low Earth orbit satellites] disproportionately affect science programs that require twilight observations, such as searches for Earth-threatening asteroids and comets, outer Solar System objects, and visible-light counterparts of fleeting gravitational-wave sources,” NSF wrote in a report.
On its own, BlueWalker 3 is large enough to mess with observations of the cosmos. However, the prototype satellite is just a test to build an entire constellation of more than 100 satellites. AST SpaceMobile wants to create the first and only space-based cellular broadband network directly accessible by cell phones, sending more of its satellites to orbit by the end of 2024.
Low Earth orbit is already filling up with commercial satellites. Elon Musk’s SpaceX is building an internet constellation in low Earth orbit with plans to deploy upwards of 42,000 satellites. Amazon is also planning to launch a fleet of 3,236 satellites for Project Kuiper, while OneWeb wants to launch 648 satellites.
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