Giant satellite eclipses stars, raising new concerns for astronomers | Science

Since launch in September, the BlueWalker 3 communications satellite has been orbiting the Earth, huddled like a cocoon. Now, it has hatched, unfolding an antenna array the size of a highway billboard, its Texas-based manufacturer, AST SpaceMobile, announced today. Astronomers say the satellite’s brightness has increased by a factor of 40, rivaling the brightest stars in the sky.

“That’s exactly what astronomers don’t want,” says astronomer Meredith Rawls of the University of Washington, Seattle, who helps run the Center for the Protection of the Dark and Quiet Sky from Satellite Constellation Interference at the International Astronomical Union’s Center. for the Protection of the Dark and Quiet Sky from Satellite Constellation Interference. “It will prove to be a superb streak in the images and potentially saturate the camera detectors in the observatories.”

Thousands of commercial satellites are already scattered in low Earth orbit. The 64-square-meter BlueWalker 3 is the largest ever made, considerably brighter than any Starlink satellite deployed by SpaceX, says astronomer John Barentine of Dark Sky Consulting. In addition to light pollution, BlueWalker 3 is testing a transmission technology that threatens to trespass into the frequencies used by radio observers on Earth, he says. “This looks fundamentally different,” he says. “We are in new territory here.”

AST SpaceMobile hopes the satellite will pave the way for the first space-based cellular broadband network by improving coverage by transmitting radio waves directly between satellites and cell phones rather than transmitting signals through cell towers. To reach the phones on the ground, the satellite uses a large reflective antenna the size of a squash court that shines brightly as it orbits.

BlueWalker 3 is a prototype for a constellation of 168 even larger satellites called BlueBirds. AST SpaceMobile CEO Abel Avellan said his fleet, which would pale in comparison to the tens of thousands of planned Starlink aircraft, will not interfere with optical astronomy. But Barentine says even a small crew of these larger, brighter orbiters will hamper ground-based telescopes’ ability to detect space objects, including potentially dangerous asteroids.

There are even brighter objects in the sky with a history of photobombing telescopes. For example, the International Space Station (ISS) is typically around 40 times brighter than recent BlueWalker 3 observations. But astronomers have real-time access to the precise location of the ISS, allowing them to refocus their cameras or close their shutters. when it passes. AST SpaceMobile has not yet responded to requests from astronomers to provide them with directions on the whereabouts of its satellite, nor has it responded to a request for comment on this article. “We are trying to do it in a spirit of cooperation,” says Barentine, “but there are still many companies we haven’t heard of yet.”

Optical astronomers aren’t the only researchers threatened. The direct-to-mobile cellular service that BlueWalker 3 and its successors aim to provide requires a much stronger range and wider use of the radio spectrum than existing networks, causing concern among radio astronomers. On Earth, various regulatory bodies prohibit companies from operating in protected “radio silent zones” and from using certain frequencies that radio observers use to probe the universe. But those regulations don’t apply to space.

“[Direct-to-mobile technology] it’s something that simply shouldn’t happen in terms of radio astronomy, ‚ÄĚsays Harvey Liszt, a radio astronomer at the National Radio Astronomy Observatory. “The use of the spectrum simply becomes free for everyone … and at that point, the whole universe is simply bright for radio astronomers.”

Liszt and her colleagues filed a complaint with the Federal Communications Commission (FCC) in December 2020, shortly after AST SpaceMobile proposed testing direct-to-mobile broadcasting in Hawaii and Texas. FCC finally granted an experimental license to BlueWalker 3, but has not yet approved the proposal for BlueBirds’ larger fleet.

The underlying problem, Barentine says, is that policies governing broadcasting from space were written in the 1960s, before private satellite constellations became commercially viable. “The system we have right now is not very well equipped to deal with a scenario like this, which is moving forward at full speed,” he says.

Astronomers are pinning their hopes on extending environmental protection to space. The National Environmental Policy Act requires US agencies to consider environmental impacts before approving projects, but satellite licenses were exempted because space was not considered part of the Earth’s environment. This hypothesis is now disputed. On November 2, the US Government Accountability Office (GAO) urged the FCC to review how the act applies to satellite constellations. The day after the GAO report, FCC announced the creation of its new Space Bureau and Office of International Affairs. Barentine hopes it is a signal “of the beginning of a change in the supervision of US commercial activities in space”.

For now, astronomers must learn to share the skies with the glittering machines. “This is the water we swim in,” says Liszt. “All we want everyone to do is stay in their own lane.”

Leave a Reply

%d bloggers like this: