Reflect Orbital's space mirrors could shine 10,000 times brighter than the moon, study finds

Reflect Orbital, a US company, plans to launch a test satellite called Earendil-1 later this year that will extend an 18-by-18-meter mirror in orbit. The test is meant to prove out a much larger plan: launching up to 50,000 satellites, each measuring 54 by 54 meters, that would reflect sunlight down to Earth on demand. The company has said the goal is to prolong daylight hours for uses including solar panel charging, emergency response and military activities, and that it eventually wants to place satellites high enough to provide light around the clock to locations on the ground. The Federal Communications Commission approved the Earendil-1 launch in July.

A new paper by Miroslav Kocifaj, an astronomer at the Slovak Academy of Sciences, and colleagues, accepted for publication in Astrophysical Journal Letters, calculates how far the reflected light would scatter beyond its intended target. Within the beam's intended circular target area, five kilometers across, a single satellite would appear about 40 times brighter than the full moon. As far as 14 kilometers from the center of the beam, it would still be as bright as the full moon. Combining the beams of 400 satellites, which Reflect Orbital eventually plans to do, would produce light as bright as 10,000 full moons within that five-kilometer area, equal to 2.4% of the sun's brightness, and the combined beam would remain visible as a glow above the horizon as far as 80 kilometers away. Olivier Hainaut, an astronomer at the European Southern Observatory, had previously modeled the broader effect separately and found the beams could brighten the sky by up to 300% worldwide; he called Kocifaj's new figures unsurprising but useful, saying the two papers together "really cover most of it."

Reflect Orbital CEO Ben Nowack disputed the paper's findings, saying "some assumptions are simply inaccurate" and that the company's safeguards, including exclusion zones, already account for scattering. He said the company has engaged with concerns raised by astronomers and other researchers and that the feedback has shaped its technology and operations. Kocifaj responded that Reflect Orbital has not backed its claims with data: the company states that safeguards exist and that scattering is accounted for, he said, "but it gives no numbers, no description of the model, no assumptions, and no data," leaving nothing to technically engage with, while his own calculations produce concrete figures.

In August, a group of organizations including DarkSky International and the American Bird Conservancy urged the FCC to reverse its approval of Earendil-1 and require a formal public-interest and environmental review under the National Environmental Policy Act, citing risks to astronomy, aviation and wildlife alongside the light pollution concerns. Space lawyer Michelle Hanlon, of the University of Mississippi's School of Law, said the FCC's authority is limited to licensing the radio frequencies used to communicate with the satellites, not the operation of the mirrors themselves, meaning Reflect Orbital will need separate national and local permissions to reflect sunlight onto the ground. If the beams spread as far as Kocifaj's team predicts, she said, the company could need approvals in more than one jurisdiction, along with answers to aviation-safety and cross-border questions. Reflect Orbital's own March filing with the FCC also noted that observing Earendil-1 through a telescope larger than 12 inches, an aperture many astronomers have access to, may be unsafe for human eyes, though it said resulting injury is unlikely because the satellites are not constantly bright.

Key facts

Reflect Orbital plans to test an 18-by-18-meter orbital mirror on the Earendil-1 satellite this year, en route to a fleet of up to 50,000 satellites measuring 54 by 54 meters each.
A study accepted by Astrophysical Journal Letters finds a single satellite would shine about 40 times brighter than the full moon within its 5-kilometer target zone, and still moon-bright 14 kilometers away.
Combining 400 satellites' beams, as Reflect Orbital eventually plans, would produce light as bright as 10,000 full moons in the target area and a glow visible up to 80 kilometers out.
The FCC approved the Earendil-1 launch in July, but DarkSky International and the American Bird Conservancy are now pushing the agency to reverse that approval and order a formal environmental review.
Reflect Orbital CEO Ben Nowack disputes the study's assumptions, but astronomer Miroslav Kocifaj says the company has not released data to support its safeguard claims.

Why it matters

This is the first detailed, peer-reviewed quantification of how far Reflect Orbital's reflected sunlight would scatter beyond its stated target zones, and it lands just as the company is preparing to launch its first test satellite. With a roadmap of up to 50,000 satellites eventually planned, the gap between the company's intended footprint and the study's measured one is not a rounding error: it is the difference between illuminating a chosen patch of ground and altering the night sky over a much wider area.

Who it affects

Astronomers lose usable dark sky far beyond any single target zone, since the study finds moon-level brightness 14 kilometers from a beam's center and a visible glow up to 80 kilometers away once hundreds of satellites combine. Environmental and wildlife groups, including the American Bird Conservancy, are concerned about nighttime ecosystems. Aviation and cross-border regulation are also implicated, according to space lawyer Michelle Hanlon, and residents near future target areas would be the ones experiencing the extra light, whether or not they requested it.

How to use it

There is no product here for the public to buy or opt into: Reflect Orbital's stated use cases are solar panel charging, emergency response and military activities, sold to operators who would request reflected sunlight on demand. For anyone tracking the story, the concrete next step is the FCC review that DarkSky International and other groups are now demanding; the agency's response will determine whether Earendil-1's approval stands as the company works toward its larger constellation.

How solid is it

Kocifaj's paper has been accepted for publication in Astrophysical Journal Letters, a peer-reviewed journal, and its conclusions are corroborated by a separate, earlier model from Olivier Hainaut at the European Southern Observatory, who found the beams could brighten the sky by up to 300% worldwide. Hainaut, who was not involved in the new paper, described its authors as competent modelers and called the two studies together a fairly complete picture. Reflect Orbital disputes the assumptions but, per Kocifaj, has not published data or a model of its own to counter the figures.

Risks and caveats

The dispute is unresolved: Reflect Orbital says its exclusion zones already account for scattering, while Kocifaj says the company has offered no numbers or methodology to check that claim against. The FCC's own authority is narrower than it might appear, covering only the radio spectrum used to talk to the satellites rather than the mirrors' operation, so Reflect Orbital may need separate, multiple jurisdictions' approval to actually reflect light onto the ground. The company's own March FCC filing also flagged that viewing Earendil-1 through a telescope larger than 12 inches may be unsafe for human eyes, even though it considers significant injury unlikely. No launch date beyond "later this year," no timeline for scaling toward 400 or 50,000 satellites, and no cost figures for the service are given in the source.

“This is incompatible with astronomy. There is no way you can do this and preserve dark skies.”

— Samantha Lawler, astronomer at the University of Regina