As SpaceX’s Starlink Ramps Up, So Could Light Pollution

“It’s going to be difficult to compete against SpaceX in this domain, given its obvious advantage in launch. Competitors exist and are being formed, however, suggesting that the market still sees opportunity,” wrote Matthew Weinzierl, an economist at Harvard Business School who researches the commercialization of the space sector, in an email to WIRED.

A representative from SpaceX’s communications team declined interview requests from WIRED.

But a representative from Amazon indicated the company is aware of potential light pollution issues. “Reflectivity is a key consideration in our design and development process. We’ve already made a number of design and operational decisions that will help reduce our impact on astronomical observations, and we’re engaging with members of the community to better understand their concerns and identify steps we can take,” the spokesperson wrote by email.

Katie Dowd, OneWeb’s director of government and corporate affairs in North America, wrote in an email to WIRED that the company is talking with groups, including the UK’s Royal Astronomical Society and the American Astronomical Society, to understand the effects satellites have on observations, “and to create design and operational practices that support both communities. We are also undertaking brightness measurements and will be looking at those results to explore solutions.”

SpaceX and its rivals can’t avoid light pollution; they can only reduce it. Every object in the atmosphere reflects at least some light during part of its orbit, depending on its materials, color, and size. While satellites beam information down to Earth, a tiny bit of sunlight often gets reflected down, too, both by a satellite’s body and its solar array.

Early last year, SpaceX tested a Starlink satellite nicknamed Darksat, giving it an experimental darkening coating on one side, including the antennas, to cut down on the reflective brightness, which the company claims was reduced by 55 percent. In one paper, some astronomers found that the measure did darken the satellite but not to that degree, though it made the satellite invisible to the naked eye. Others didn’t detect significant darkening at all. They found that the satellite’s measured brightness may vary, however, depending on the angle at which it’s observed and how the light scatters through the atmosphere. 

According to a post on the company’s website, SpaceX found that the dark surfaces got hot, putting the satellite’s components at risk, and that it still reflected light in the infrared. So the company later tested a different approach that it calls Visorsat, deploying a number of satellites with rectangular sun shades attached, like the one used on a car windshield. Those visors are intended to make sure that sunlight that bounces off the satellites’ antennas is reflected away from Earth. 

So far, SpaceX hasn’t publicly released any information about how well this approach works, or how it compares to Darksat. But another astronomer, in an unpublished paper posted on the academic preprint server arXiv.org, and Boley’s team in work-in-progress, both independently find that at least 70 percent of the Visorsat spacecraft were still brighter than their preferred threshold: a level that would ensure that the Vera C. Rubin Observatory’s images will be mostly unaffected.

To draw attention to light pollution concerns and to work on developing solutions, the American Astronomical Society convened a virtual workshop on satellite constellations this summer, known as SatCon2. They plan to soon issue reports and recommendations, coinciding with a meeting beginning this Sunday, called “Dark and Quiet Skies for Science and Society,” organized by the United Nations and the International Astronomical Union.

SatCon2 organizers made a priority of reaching out to a broad range of people concerned about the night sky, including amateur astronomers, astrophotographers, the planetarium community, environmentalists, and indigenous and tribal communities from the United States, Canada, New Zealand, and other countries. “Everybody wanted things to slow down. They want industry to engage more. This is something that belongs to everyone as a global commons,” says Amina Venkatesan, an astrophysicist at the University of San Francisco and SatCon2 public engagement co-chair. 

As part of SatCon2, a working group of astronomers spoke with representatives from SpaceX and five other major satellite operators about what reflected light limits researchers propose, and how the companies could assess and reduce how reflective their spacecraft are. They also debated policy options within the US that could involve setting rules for how much light pollution internet satellites can create. These include the possibility of regulations imposed by the Federal Aviation Administration, which sets conditions for launch and reentry, or the FCC, which licenses radio frequencies in orbit. Some astronomers also would like to see the National Environmental Policy Act to end its exemption for space—that is, they see space as an environment in need of protection.