A U.S. company called Reflect Orbital has proposed an ambitious, and controversial, project to deliver “sunlight on demand” after dark by deploying a constellation of mirror satellites, says Tech Xplore. The idea is to bounce sunlight off large mirrors in orbit so that solar farms can continue generating power during nighttime or low-light periods.
Their first step is Earendil-1, an 18-meter test satellite planned for launch in 2026. If the technology works, it could scale to thousands of satellites by 2030, each with solar reflectors spanning tens of meters. The vision is to beam 200 watts per square meter, roughly 20% of peak midday sun, onto Earth’s surface. But doing so would require a massive constellation of mirrors to maintain continuous illumination.
In practice, the physics limits how focused that reflected light can remain. Because the sun appears as a disc in the sky (not a point source), reflections spread over distance, making the illuminated ground patch wide and dim. For a single 54-meter mirror satellite in low Earth orbit, reflected light is estimated to be 15,000 times fainter than noon sunlight, though still far brighter than moonlight. The beam would need to cover an area several kilometers wide to be practical, reducing intensity further.
A balloon test helped validate the concept: a 2.5-meter mirror suspended at 242 meters delivered about 516 W/m² to solar sensors, around half the brightness of midday sun. But scaling that to orbital distances is a very different challenge.
Critics point out serious concerns. First, the cost and complexity of launching and coordinating thousands, or even hundreds of thousands, of mirror satellites would be enormous. Second, switching between target locations is hard: satellites in low Earth orbit only stay over a specific area for a few minutes, so maintaining continuous coverage demands huge satellite density. Third, the project could wreak havoc on astronomy. Mirror satellites intentionally reflecting bright light may outshine stars, confuse telescopes, and degrade observations of the night sky.
Reflect Orbital plans to “redirect sunlight in ways that are brief, predictable and targeted,” share satellite trajectories to help astronomers avoid conflict, and exclude observatories from illumination paths. But critics remain skeptical of how much control or safety it affords.
The idea of beaming sunlight at night stretches both engineering and ethics. It faces technical hurdles, astronomical consequences, and questions about whether we should pursue such an intervention in our skies, even if it were possible.