‘Not cool’: telescope faces interference from space-bound satellites

A flagship observatory that will map the heavens in spectacular detail and search the skies for asteroids on a collision course with Earth faces serious disruption from a new wave of satellites bound for space, the Guardian has learned.

Astronomers on the Large Synoptic Survey Telescope, a state-of-the-art observatory due to open in Chile next year, have discovered that its views of the night sky will be marred by thousands of highly reflective communications satellites being launched by SpaceX, Amazon and other firms.

Researchers on the LSST ran simulations to assess how the telescope would be affected by proposed launches over a decade of planned observations. They found that in some scenarios, almost every image the telescope takes will be spoiled by at least one bright streak produced by satellites passing overhead.

The scientists modelled the impact of companies launching 50,000 internet satellites into low Earth orbits over the next decade, in line with stated aims. The greatest disruption was to twilight observations, which are crucial for some areas of astronomy, and useful for spotting Earth-bound asteroids coming from the direction of the sun.

“Astronomical twilight is really, really dark, but about 90% of all our exposures with LSST will have a bright saturated trail across them,” said Tony Tyson, a professor of physics at the University of California, Davis, and chief scientist on the LSST. “At midnight in the summer, about 25% will have a trail, according to our simulation. That’s a huge hit on LSST observing.”

The disruption will affect the telescope’s efforts to study the 96% of the observable universe that remains a mystery to scientists, notably the dark energy said to be driving the expansion of the universe, and the dark energy that lurks unseen around galaxies.

“It’s a hardship for astronomy. The community is looking forward to this new view of the universe and it’s compromised,” Tyson added. The search for potentially civilisation-ending asteroids will also be disrupted.

Astronomers have been racing to understand the impact of future satellite launches since May when Elon Musk’s SpaceX sent up the first 60 of what is expected to become a 12,000-strong internet satellite constellation.

That first batch of satellites caused immediate alarm by creating highly visible trains of bright lights in the night sky. But while the satellites become too faint for the naked eye once they are moved up to their operating altitude, they can still be seen by telescopes.

This week, astronomers on the Cerro Tololo Inter-American Observatory in Chile, had their viewing disrupted by 19 Starlink satellites, part of a batch launched earlier this month. Clarae Martínez-Vázquez, an astronomer, tweeted: “Rather depressing … This is not cool.”

Tyson’s calculations suggest the LSST will be more seriously affected than any other ground-based telescope. It is particularly vulnerable because it observes the entire sky multiple times each week. On a single night, it will take 1,000 exposures, each covering a square as wide as 40 moons in the sky. In all, the astronomers will make 30tn observations of 40bn objects. Construction and operation costs for the decade stand at $1.3bn.

“It’s designed to scan the sky as rapidly and as deeply as physically possible and that’s exactly the prescription for running into these things,” Tyson said. To the 12,000 satellites already planned, SpaceX may add a further 30,000. Other companies, such as Amazon, OneWeb and Samsung, are interested in launching their own constellations.

A months-long effort to remove the streaks by processing the images has so far failed. And while it is possible to reschedule the telescope’s observations to dodge small numbers of satellites, it cannot avoid 50,000. “It turns into a wild goose chase. It turns out to be even worse than not doing anything because you end up losing telescope time in a major way,” Tyson said.

“There needs to be some kind of international regulation. It’s going to take a long time for that to occur, and I suspect it will eventually, but at the moment I think it’s the court of public opinion that matters more,” he added.

SpaceX is working with the astronomers to mitigate the damage and is taking steps to make the bottoms of its future satellites black so they reflect less sunlight. The firm said it would also adjust the orbits of its satellites to avoid disrupting extremely sensitive space science observations.

“The LSST is clearly the project people are most worried about. It’s the biggest, fastest, meanest survey telescope coming down the line and the most sensitive to very bright satellites,” said Patrick Seitzer, an astronomer at the University of Michigan who has run detailed analyses on the Starlink satellites.

“We are certainly encouraging companies to design their satellites so that the Earth-facing surfaces are as faint as possible, but there are limits to what you can do. If you paint them black, they absorb sunlight and they get hot and that damages the electronics.

“There’s a balance to be struck. We don’t want to stand in the way of progress in bringing low-cost internet to the entire world, particularly places that don’t have it. There are real social benefits to building these constellations. But the trade off is they will change the appearance of the night sky.”