The U.S. Cleared a Giant Space Mirror to Shine Sunlight After Dark and Turn Night into Day

A startup’s orbital test could illuminate Earth — and darken astronomy’s future.

The night sky may soon acquire a switch.

A California startup plans to send an enormous, steerable mirror into orbit and use it to bounce sunlight onto selected patches of Earth after sunset. On July 9, the Federal Communications Commission authorized Reflect Orbital to deploy and operate Eärendil-1, a prototype satellite carrying a reflective film roughly 59 feet, or 18 meters, across.

In effect, the satellite would be able to make day out of night on a selected surface of the planet.

This first test could show whether “sunlight on demand” can move beyond science fiction, allowing certain regions to bask in sunlight 24/7, with important applications in solar energy and agriculture. Reflect Orbital ultimately envisions more than 50,000 mirror satellites by 2035. But not everyone is on board with the idea.

The main critics are astronomers who warn that a fleet on that scale could overwhelm telescopes and visibly transform the night sky. The current approval covers only one experimental spacecraft, not the proposed constellation.

How Do You Deliver Sunlight from Space?

According to the FCC’s July 9 authorization, Eärendil-1 will orbit about 625 kilometers above Earth and use a motorized, thin-film reflector that can aim sunlight at a designated target. Reflect Orbital says the illuminated area could span at least five kilometers.

The satellite will catch sunlight while flying above the dark side of Earth, then sweep a reflected patch across the ground. A single low-orbiting spacecraft can provide only brief illumination. Longer service would require many satellites passing in succession.

Reflect Orbital says those beams could help search-and-rescue crews, light disaster zones and remote construction sites, extend crop-growing cycles and let solar farms generate power beyond sunset. Its public roadmap calls for two satellites in 2026, more than 5,000 by 2030 and more than 50,000 by 2035. The company says future fleets could adjust light from moonlike levels to daylight brightness like a dimmable switch.

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Astronomers Are Not Happy

To astronomers, the concerns are serious. A mirror can also appear as an extraordinarily bright moving object, leave streaks across telescope images and scatter light through the atmosphere.

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A recent European Southern Observatory modeling study estimated that, with 50,000 Reflect Orbital satellites, every exposure from a wide-field camera like the one at the Vera C. Rubin Observatory could be lost whenever the mirrors remained sunlit. The researchers also calculated that the full fleet could make the overall night sky three to four times brighter, even while operators avoided pointing beams near observatories. These are projections for the proposed constellation, not measured effects from Eärendil-1.

“For optical astronomy, this is an existential threat, and we hope that the regulators will share that view,” Betty Kioko, an institutional affairs officer at the European Southern Observatory, said before the decision.

The FCC received more than 1,800 comments on the proposal, including objections from astronomy and dark-sky groups. But the agency said its authority centered on satellite communications and radio frequencies. “We find that concerns about Earendil-1’s impacts on optical astronomy fall outside our review and authorization of the space station,” the FCC wrote in its order.

The agency also declined to require a fuller environmental assessment. Commenters cited risks to birds, insects and other wildlife that use darkness to navigate, reproduce or hunt, as well as concerns about human sleep and aviation. The FCC found those claims insufficiently specific for one satellite and declined to consider the effects of a hypothetical fleet. Any constellation would need its own application and authorization.

An Old Idea Returns at a Much Larger Scale

Space mirrors have reached orbit before. In 1993, Russia deployed Znamya 2, a 20-meter reflector attached to a Progress spacecraft. It cast a roughly five-kilometer patch of light across Europe while racing over the ground at about eight kilometers per second. The effect lasted a few minutes. A larger follow-up mirror snagged on an antenna during deployment in 1999, ending the experiment. NASA’s account of the project shows that reflecting sunlight was indeed practically possible; controlling it reliably and making it useful proved harder.

Reflect Orbital says its satellites will remain off by default, avoid observatories and sensitive habitats, and operate only with local authorization. “Every spot of light Reflect delivers will be requested, approved and contained,” the company said in May.