The BlueWalker 3 satellite, with an antenna surface area of up to 64m2, will reflect a significant amount of sunlight, hindering celestial observations.
The BlueWalker 3 satellite from the American company AST SpaceMobile was launched into orbit by SpaceX’s Falcon 9 rocket from the Kennedy Space Center in Florida at 9:20 PM on September 10 (local time). The satellite is designed to test a mobile connectivity technology, including 4G or 5G internet, directly from the satellite to phones, helping to provide coverage in remote areas.
Illustration of the BlueWalker 3 mobile phone service satellite from AST SpaceMobile in orbit. (Image: Nokia/AST SpaceMobile).
Orbiting the Earth at an altitude of 500 km, this 1,500 kg satellite will deploy a giant 8-meter-long antenna with a surface area of 64m2—equivalent to the size of a tennis court. This flat and large surface will reflect a substantial amount of sunlight, potentially making the satellite extremely prominent when observed from the ground.
For astronomers, satellites like this will create bright streaks in images taken from ground-based telescopes, obstructing the observation of distant celestial bodies. “We are concerned. BlueWalker 3 could be the brightest object in the night sky, even brighter than Venus,” said John Barentine, an astronomer at Dark Sky Consulting. Venus is currently the second brightest object in the night sky, after the Moon.
Barentine is also worried about the satellite’s technology that transmits signals directly to mobile phones. This technology requires a strong radio wave beam to connect with users’ phones, which could interfere with radio astronomy, a field that relies on ultra-sensitive equipment to study the universe. “We are concerned about the power levels in that beam,” Barentine stated.
AST SpaceMobile plans to launch around 100 larger satellites than BlueWalker 3, named BlueBirds, starting in 2023. These could be more than twice the size of BlueWalker 3 and even brighter. “The brighter the object, the more damage it can cause to night sky photographs,” Barentine added.
International law does not limit the size of satellites, but the recent launch may highlight the limitations in existing regulations, according to Chris Johnson, a space law advisor at the Secure World Foundation. “I see this as an infringement on astronomers’ rights to explore space,” he said.
The U.S. Federal Communications Commission (FCC) has granted a testing license for BlueWalker 3. However, the full license for AST SpaceMobile’s subsequent satellites may depend on the performance and impact of BlueWalker 3.
“Most astronomers accept that there will be more satellites in the future. What they want is to ‘coexist’ peacefully. We cannot make satellites invisible,” Barentine remarked.
