Space mirror plan raises concerns over night-sky impacts

Reflect Orbital plans to launch Eärendil-1 later this year, a test satellite designed to deploy an 18-by-18-meter mirror in orbit. The US company has outlined longer-term ambitions for up to 50,000 larger satellites, measuring 54 by 54 meters, to reflect sunlight to Earth for uses including solar charging, emergency response, and military activities.

A new study led by Miroslav Kocifaj of the Slovak Academy of Sciences found that a single satellite could appear about 40 times brighter than the full moon within its intended five-kilometer target area. The satellite could still match the full moon’s brightness as far as 14 kilometers from the beam center. A combined beam from 400 satellites could reach the brightness of 10,000 full moons in the target area, or 2.4% as bright as the sun, with visible glow up to 80 kilometers away.

Astronomers and environmental groups have challenged the Federal Communications Commission’s approval of Eärendil-1, citing risks to astronomy, wildlife, aviation, and the nighttime environment. Reflect Orbital CEO Ben Nowack disputed the study’s assumptions and said safeguards account for scattering, while Kocifaj said the company has not provided data detailed enough for technical review.