SPACEX’S STARLINK CATCH ASTRONOMERS OFF GUARD

The satellites launched so far are much more visible than expected

SpaceX founder and CEO Elon Musk announced the Starlink concept back in January 2015, explaining the company intended to launch about 4,000 broadband satellites into low-Earth orbit to provide low-cost internet to people around the world.

The envisioned numbers have grown since then. SpaceX now has permission from the US Federal Communications Commission to loft about 12,000 Starlink craft, and the company has applied to an international radio-frequency regulator for approval of up to 30,000 additional satellites. For perspective, there are only about 2,000 operational satellites in orbit today, and humanity has launched only around 9,000 craft into space in all of history.

Shortly after deployment, the Starlink craft look like a bright string of pearls as they race together across the sky. This formation disbands as the 225-kilogram (500-pound) satellites disperse and climb to their final operational altitude about 550 kilometres (342 miles) above Earth’s surface – but the individual spacecraft remain visible to the naked eye, even way up there.

“What surprised everyone was how bright their satellites are,” said Patrick Seitzer of the University of Michigan. “We knew these megaconstellations were coming, but based on the sizes and shapes of things currently in orbit, I thought maybe eighth or ninth magnitude,” Seitzer added. “We were not expecting second or third magnitude in the parking orbits, and we were certainly not expecting fourth to fifth magnitudes in the [operational] orbits.” This surprising brightness has many astronomers worried. The huge number of coming Starlink satellites could severely compromise the ability of groundbased telescopes to do their work.

The high-profile project most likely to be affected is the Vera Rubin Observatory, scheduled to come online a few years from now in the Chilean Andes. “The survey is the most impacted by bright satellite trails because of its wide field of view and extreme sensitivity,” Seitzer said.

But Starlink’s effects will be felt beyond the astronomical research community – indeed, by pretty much everyone around the world. The star-filled night sky is an international resource, and one of the only ways that many people commune with nature in our increasingly urban and technological world, said Ruskin Hartley, executive director of the International Dark Sky Association. “The night sky is the ultimate public good; it’s our ultimate commons,” Hartley said during a news conference. “No one individual can protect it. And the flip side, I believe, [is] no one individual should be allowed to despoil that.”

Astronomers have voiced their concerns to

SpaceX and found a receptive audience, said Jeffrey Hall, the director of Lowell Observatory in Flagstaff, Arizona. “We have not had to cajole SpaceX in any way; they’ve been very receptive, very proactive, in holding roughly monthly telecons with us,” said Hall. “It’s been a little more staying in touch than making a lot of progress on mitigation.” One of the 60 spacecraft that launched in January sported a special coating designed to reduce its brightness. If everything goes well, and the coating doesn’t seriously affect the satellite’s performance, this mitigation measure could eventually become widespread.

Not everyone is satisfied by such steps. Astrophysicist and science communicator Ethan Siegel asked: “Why should astronomers trust SpaceX – which knows about this problem but is deliberately worsening this instead of addressing it before additional launches – instead of seeking a legal or international mandate for regulation?” In response, Hall explained that the astronomy community doesn’t really have much choice. “The launches are underway right now. I think regulation of the Wild West up there is necessary; that is going to take a great deal of time to implement, just because of the nature of that beast,” Hall said. “Therefore, there is no advantage or upside to distrusting what SpaceX colleagues have told us,” he added. “We will simply take them at face value and work as best as we can and honestly with them to try to solve the situation.”