March 1, 2024

How SpaceX is changing Starlink satellites to keep skies dark for science

SpaceX uses Falcon 9 rockets to carry batches of about 60 Starlink satellites at a time.
Paul Hennessy/Sopa Images/LightRocket via Getty Images

  • SpaceX became astronomers’ biggest enemy when it started launching Starlink internet satellites.
  • But SpaceX worked with scientists to try to reduce the brightness of satellites in telescope images.
  • Some of SpaceX’s solutions work. Other megasatellite ventures, like Amazon, are taking notice.

NEW ORLEANS – When SpaceX launched its first Starlink satellites, astronomers around the world freaked out and the company quickly became a villain of the skies.

“I felt as if life as an astronomer and lover of the night sky would never be the same,” astronomer James Lowenthal told New York Times in 2019.

As the glowing trail of satellites soared through space, ascending to their target orbit in May 2019, people outside could see them clear as day, passing overhead as they circled the Earth.

To some, it seemed to herald the end of astronomy. “If there are a lot of bright moving objects in the sky, that complicates our work tremendously,” Lowenthal told the Times.

But for rural populations, including in developing countries, that lack reliable Internet, Starlink could make a huge difference as SpaceX aims to blanket the Earth with high-speed broadband Internet, courtesy of more than 10,000 satellites. .

However, Starlink satellites – now numbering more than 5,000 satellites – are intersecting astronomers’ view of the cosmos, ruining their data. Even some telescopes in space are not safe. Last year, a study found that about a third of Hubble Space Telescope images could be ruined by satellites by 2030.

SpaceX leads the way for change

A satellite trail passes in front of galaxies in this Hubble Space Telescope image.
NASA/ESA/Kruk et al.

SpaceX is not alone in this endeavor; it was just the first company to get huge batches of shiny spacecraft off the ground. At least a dozen companies, as well as the Chinese government, are planning to launch their own satellite megafleets.

Many astronomers see the emerging business of Internet satellite constellations as an existential threat. But of all the companies rushing to claim this new frontier, SpaceX has calmed some of its critics by listening to them, working with them and trying to obscure its satellites.

“Now we’re making progress,” Jonathan McDowell, an astronomer who has been one of Starlink’s most outspoken critics, told Business Insider at an American Astronomical Society conference in New Orleans.

Three different satellite trails obscure the stars in a Hubble Space Telescope image.
NASA/ESA/Kruk et al.

McDowell and other astronomers met with satellite industry representatives to discuss efforts to keep the skies dark and quiet.

No current SpaceX representatives attended the session. Still, Starlink’s experimental solutions dominated the conversation — perhaps because it’s the only company trying the solutions suggested by astronomers.

“For me, the focus is not just on alert, but on the path to coexistence,” Patricia Cooper, a satellite industry consultant and former vice president of government affairs for satellites at SpaceX, told the assembled astronomers. “It’s not surprising that we haven’t solved the problem in four and a half years.”

SpaceX experimented with black paint, sun visors and now ‘mirror film’

CEO Elon Musk has said little publicly about astronomers’ concerns, but SpaceX has worked privately with astronomy leaders.
Slaven Vlasic/Getty Images

SpaceX threw a handful of spaghetti at the wall to dim its satellites, and some things got stuck.

In 2020, about six months after Starlink’s first glowing trail slid across the skies, SpaceX launched its first noodling to solve the problem, essentially painting a bunch of satellites black.

That kind of helped. The satellites were less bright, but were still very bright.

Later that year, SpaceX tried using sun visors to block sunlight from reaching the bottom of satellites, where it could reflect back to Earth and make them appear shiny.

That worked. Satellites with visors were about a third brighter than those launched without visors. But they were still bright enough to interfere with astronomers’ data. Displays were a regular feature for many Starlink satellites until SpaceX added laser communications. The visors blocked the lasers, so they had to leave.

Now SpaceX is researching a “mirror film” that could further reduce glare on its next Starlink generation. However, these satellites are much larger than the old ones, “so that kind of cancels itself out,” McDowell said.

“I don’t think there are all the villains or heroes here,” he added.

SpaceX developed its solutions through meetings with astronomers, including the world’s first satellite glow conference. In 2022, the International Astronomical Union formalized this ongoing collaboration as the Center for the Protection of Dark and Quiet Sky from Satellite Constellation Interference — CPS for short.

SpaceX even adopted an operational tweak suggested by astronomers — pointing the satellites’ solar panels away from the Sun as they pass over the line between night and day. This is when they appear over the horizon and are most damaging to Earth’s telescopes. Giving the solar panels less sun at this time helps astronomers, but means less power for the satellite.

“That’s a real, substantial mitigation that they’ve done,” McDowell said. “They’re actually losing money on this. So we appreciate that.”

“Whether other companies do so remains to be seen,” he added.

Amazon and other companies may follow SpaceX’s example

Amazon and a small Earth imaging company called Planet Labs are following SpaceX’s lead.

Chris Hofer, international team leader for Amazon’s Project Kuiper internet satellites, told astronomers in New Orleans that SpaceX’s Starlink tweaks were helpful.

Since joining CPS, Hofer said Amazon has begun improving its solar panels and researching sunglasses.

Both Hofer and Kristina Barkume of Earth imaging satellite company Planet said they would follow SpaceX’s new mirror film tests with interest.

“These innovations help us,” Barkume told Business Insider.

Although some companies seem to be paying lip service to, or even throwing money at, the shiny satellite problem, it probably won’t go away.

The next few years could see tens of thousands of satellites crowding Earth’s orbit. No matter how bright they are or not, they are almost certain to interfere with astronomy. Scientists will have to find ways to peer through the gaps between satellites, however small or fleeting these windows into the cosmos become.

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