This new satellite that has become too bright irritates astronomers

On September 10, 2022, the BlueWalker 3 satellite was placed into orbit around the Earth aboard a SpaceX Falcon 9 launch vehicle. very significant light, according to astronomers.

In September 2022, the first AST SpaceMobile satellite, BlueWalker3, was launched into orbit around the Earth using a SpaceX Falcon 9 rocket. The objective is similar to that of the Starlink constellation: to transmit the Internet, here 4G and 5G directly from space, therefore no wired connection. The idea is aimed at rural populations or in low-density areas, where the wired network is non-existent. For now, only BlueWalker3 has been placed into orbit at an altitude of 500 kilometers. But AST SpaceMobile’s goal is to add another 110, called BlueBirds, to form a constellation that could bring the Internet anywhere on Earth. This network would then be “first and only space-based cellular broadband network to be accessible by standard smartphones”, explains the company on its website.

Assembly, launch and deployment of the BlueWalker3 satellite. © AST SpaceMobile, YouTube

Satellite constellations make the sky very clear

But, problem: since BlueWalker 3 deployed its array of antennas, its luminosity has increased 40 times, so the satellite eclipses an entire part of the night sky and competes with the brightest stars. With a surface area of ​​64 m² and a mass of 1,500 kg, the machine does not, however, reach the size of the future BlueBirds, scheduled to be launched in 2023. Scienceinvolving astronomers, warn of the consequences of light pollution created since 2020, and which continues to increase. “This is exactly what astronomers don’t want”said Meredith Rawls, an astronomer at the University of Washington who helps run the International Astronomical Union’s Center for Protecting Dark and Calm Skies from Interference from Satellite Constellations. “It will show up as a super bright band in the images and potentially saturate the camera detectors in the observatories. »

Currently, other man-made objects exceed the luminosity of BlueWalker 3, including the International Space Station (ISS). However, each of its passages in the sky is known to astronomers, so their observations adapt to it! “We try to do it in a spirit of cooperation”explains John Barentine, astronomer at Dark Sky Consulting, “But there are still many companies that we haven’t heard about yet. »

Insufficient laws to control light pollution

In addition to brightness, the BlueWalker 3 is concerned because of the technology it uses. In fact, it will transmit radio waves directly to the phones in order to avoid passing through cell phone towers. But there again is the problem: the frequency band it uses, too wide, encroaches on the radio frequencies used in observatories, so that certain objects would become undetectable if the constellation were launched, including potentially dangerous asteroids. To which an AST SpaceMobile spokesperson responded: “We look forward to using the latest technologies and strategies to mitigate potential impacts on astronomy. We actively work with industry experts on the latest innovations, including state-of-the-art anti-reflective materials. »

But, goodwill of the companies or not, the root of the problem is in the legislation: on Earth, certain areas must remain silent in the radio waves, so as not to interfere with the observatories. But in space there are no rules. “The system we currently have is not very well equipped to deal with a scenario like this, which moves at full speed”lamented John Barentine.

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