Artist’s impression of a large LEO satellite constellation circling above the Low-Frequency Array telescope near Exloo, Netherlands. Credit: Danielle Futselaar/International Astronomical Union

The last time Patricia Cooper attended a meeting of the American Astronomical Society, she wasn’t sure what she was getting into.

It was January 2020 and Cooper, at the time a vice president at SpaceX, had agreed to represent the company on a panel discussion at the conference on the interference satellite constellations could create for astronomers.

That discussion was prompted by SpaceX’s first launch of 60 Starlink satellites a little more than six months earlier, widely visible in the night sky and alarming astronomers, who feared what tens of thousands of such satellites would do to their observations. “The term I kept hearing was ‘into the lion’s den,’” she recalled of preparations for the panel. “We didn’t know what was going to happen: pitchforks, rotten tomatoes?”

Despite the public outcry, fueled by social media, the actual discussion at the American Astronomical Society (AAS) meeting was polite and constructive. “It was a harbinger of how we are working now,” Cooper, now a consultant, said during a session at the most recent AAS meeting Jan. 10 in New Orleans.

In the four years that elapsed since that original discussion, the astronomy community has collaborated with SpaceX and other companies on ways to mitigate the impact of megaconstellations on optical and radio astronomy in the near term while seeking long-term regulatory solutions.

Breaking down stovepipes

The problem of satellite interference on astronomy has not been solved, astronomers made clear at the AAS meeting. “There’s some not-so-good news and some good news,” said Connie Walker, co-director of the International Astronomical Union’s Centre for the Protection of the Dark and Quiet Sky from Satellite Constellation Interference, or CPS. The not-so-good news, she said, was that the number of satellites “is increasing exponentially.”

“The good news is that companies are increasingly aware of the situation,” she continued. “Some of these companies are willing to take mitigation approaches to minimizing down below seventh magnitude.” That brightness makes satellites invisible to the naked eye and reduces their impacts on sensitive astronomical instruments.

Those efforts stemmed from “a big burst of academic research and technical analysis,” Cooper said, in the aftermath of the initial concerns about Starlink. Much of that has been coordinated by the CPS, established in 2022, working to break down stovepipes that had separated the astronomical and aerospace fields. “That’s been part of the work to try to understand that, because it helps us get to concrete steps.”

At SpaceX, that meant working on design changes to Starlink satellites to reduce the amount of sunlight they reflect to the ground. The company started with an experimental “DarkSat” with black paint. “‘Just paint everything black, dummy,’ was one of the texts that we got,” she recalled. “We knew it wasn’t going to work for thermal issues.”

SpaceX followed that with “VisorSats” with visors that kept sunlight from reaching the most reflective parts of the satellites. More than 4,500 Starlink satellites were equipped with those visors, a milestone she said some didn’t appreciate. “When there’s this sense that companies aren’t committed, it isn’t perhaps legitimate to skip over that kind of extensive industrial investment.”

The visors, though, interfere with the laser intersatellite links on newer Starlink satellites, so SpaceX has replaced them dielectric mirrors that are attached to the satellites like stickers to reflect sunlight away from the ground. The company, she added, is offering those mirror stickers as well as custom black paint at cost to other companies. “I’ve seen several satellite companies that are engaging on this.”

Astronomers acknowledge the efforts that companies like SpaceX have made on a voluntary basis. “To be clear, industry doesn’t have to play nice with us,” said Kelsey Johnson, an astronomer at the University of Virginia and president of the AAS. “They have invested real time and real money and effort to working with us that they don’t have to do.”

Lessons learned for Kuiper

While SpaceX, by far the largest satellite operator, remains the biggest worry for astronomers, other constellations are in development. That includes Amazon’s Project Kuiper, which launched its first two KuiperSat prototype satellites in October as it prepares to deploy a constellation of more than 3,200 spacecraft.

Chris Hofer, international team lead for Project Kuiper at Amazon, said at the AAS meeting that the company is following the path blazed by Starlink in dealing with astronomical interference. “The timing of this issue for Amazon was good,” he said. “We were still in the design stage of the satellites.”

Amazon initially developed a sunshade like Starlink’s visors, he said, but decided not to pursue that. It is now working with multiple suppliers for dielectric mirror films. The company installed those mirrors one of the two prototype satellites but left the other unmodified to see how effective that mitigation was.

Astronomers have been monitoring the two KuiperSats since their launch in October, but Hofer said in January that it was still premature to assess how well it was working. The company, in the meantime, was pressing ahead with other changes to spacecraft design to reduce their brightness. “We’re already internally making changes and improvements to the solar panels and few other things that we’re finding,” he said.

Hofer is one of the leaders of the “industry hub” at CPS, which works to foster collaboration between astronomers and satellite developers. “There’s a sweet spot on when it’s proper to reach out to a company,” he said, contacting them after they’ve started work on the design of the satellites but before they go into full-scale production and it’s too late to make changes.

Lack of regulations

While many companies do work voluntarily with astronomers, there is no requirement for them to do so. Of particular concern are two Chinese megaconstellations, Guowang and G60 Starlink, that combined propose to place 25,000 satellites in orbit. There is little information about what measures, if any, those constellations are taking to address their brightness.

“It is a topic that we’ve discussed a little bit within the CPS,” said Cooper when asked about discussions with the Chinese constellations. “The CPS will have to develop a strategy to deal with this.”

Even domestically, there is little astronomers can do about satellites that do interfere with their observations. An example is BlueWalker 3, a technology demonstration satellite launched by AST SpaceMobile in late 2022. Once it deployed a large phased array antenna, its brightness increased at times to magnitude 0, comparable to the brightest stars in the night sky.

BlueWalker 3 is a prototype for a constellation of even larger satellites. “There is nothing in the regulatory environment that would stop some company from launching thousands or tens of thousands of satellites like this,” said Jonathan McDowell of the Harvard-Smithsonian Center for Astrophysics. “We have to think about what’s coming.”

A still image from a video SpaceX released in September to show off dielectric mirror film added to second-generation Starlink satellites to scatter sunlight away from Earth and reduce interference with ground-based astronomy. Credit: SpaceX via X

Any sort of regulations, nationally or internationally, to address satellite constellation interference with astronomy will be a long-term effort. One issue, said Richard Green of the University of Arizona, one of the leaders of the policy hub of CPS, is figuring out what those regulations should be in an evolving industry.

“We can’t even advocate for a set of rules, like 7.0 magnitude brightness, if no company can reach 7.0 magnitude,” he said. “We have to have a phase where we can codify best efforts in some fashion and ultimately have some regulations in place that can be met.”

There have been some small steps, such as the Federal Communications Commission requiring licensees of some constellations to enter into coordination agreements with the National Science Foundation on steps to mitigate interference with optical and radio astronomy. SpaceX completed a coordination agreement with the NSF last year, and Hofer said Amazon expects to finalize a similar agreement this year.

International efforts have also been proceeding slowly. Astronomers last year sought to include an agenda item on the topic at the U.N. Committee on the Peaceful Uses of Outer Space (COPUOS), creating a new expert group to study the topic. COPUOS operates on consensus, requiring all of its hundred-plus member states to agree to include that topic for future meetings. Russia objected, saying it saw no need for a new expert group, and the proposal died.

Astronomers are instead taking a less official approach, with several nations convening a “Group of Friends” to support discussions at COPUOS. “It’s a kind of advocacy group, somewhat loosely under the auspices of the U.N., that meets and has these discussions,” said Ryan Guglietta of the State Department’s Office of Space Affairs at the AAS meeting. “The goal is hopefully feeding this into the COPUOS process and establishing that agenda item.”

Green said that, for now, the focus remains on voluntary cooperation with industry. “That can be done now and set the whole tone for how things go forward,” he said. “An industry best practice can become an expectation.”

Avoiding crisis fatigue

Astronomers and spacecraft engineers have not solved the problem of satellite interference with astronomy over the last four years. But, in the same period, the sky has not fallen — or been obscured by spacecraft — even as the number of satellites has sharply increased.

“This is an area that is ripe for crisis fatigue,” said Johnson, the AAS president. “I think it’s really important that we try, when we can, to think about the successes, even if they’re small.”

Those successes, she said, included a dedicated core of volunteers working on the issue through efforts like the CPS as well as the voluntary cooperation with industry and the NSF coordination agreements.

“It’s not a panacea, and I’m not going to argue that it is, but it’s not nothing,” Johnson said of the NSF agreements. “Sometimes not nothing is better than nothing.”

Her comments, though, illustrated the ambivalence that many astronomers still feel about satellite megaconstellations. The connectivity that broadband megaconstellations promise to offer will have benefits to society, she acknowledged, noting that the AAS mission statement states the organization will “enhance and share humanity’s scientific understanding of the universe.”

“If we want humanity to share in this, they need access to the internet,” she said. “We have to be committed to bridging the digital divide.”

However, she questioned if megaconstellations, as designed, were the best way to do so. “Bridging the digital divide does not require tens or hundreds of thousands of satellites,” she said, arguing that such systems would be used mostly for entertainment — much like any other consumer network. “To me, what this says is that we are headed towards a dystopian future where we have lost access to the universe so that people can sit in their living rooms and watch a screen on a wall.”

Cooper gently rejected those arguments. “These systems have value. They are not just nuisances,” she said, noting the interest by governments in constellations to serve their own needs.

“I’m going to push back on the doom and gloom, because that paralyzes you,” she added. “What we really need to do is see what are the things that are possible and what are the steps we need to do to get there.”

She concluded that efforts to solve the problem of satellite constellation interference in astronomy was still in its early stages. “Not surprisingly, we haven’t solved this problem in four and a half years. I didn’t think we would,” she said. “For me, the focus is not on the call to alarm, it’s on the path to coexistence.”

This article first appeared in the February 2024 issue of SpaceNews magazine.

Jeff Foust writes about space policy, commercial space, and related topics for SpaceNews. He earned a Ph.D. in planetary sciences from the Massachusetts Institute of Technology and a bachelor’s degree with honors in geophysics and planetary science...