The company Reflect Orbital has won FCC approval to launch a test satellite called Eärendil-1, the first step towards a planned fleet of up to 50,000 orbital mirrors designed to reflect sunlight onto Earth on demand. The firm envisions uses such as powering solar farms at night, boosting agricultural yields, aiding search-and-rescue operations and lighting streets or construction sites, but astronomers warn the scheme could cause serious harm to both scientific research and public safety.

The 18-square-metre mirror would produce a 5-kilometre-wide beam of light, with the satellite estimated to appear as bright as Venus outside the beam and four times brighter than the Moon within it. Experts including Roohi Dalal of the American Astronomical Society and Robert Massey of the Royal Astronomical Society have cautioned that such brightness could disrupt telescope observations, much as satellite trails have already marred Hubble images, while also risking permanent eye damage to anyone viewing the beam through a telescope and adding to harmful light pollution affecting wildlife and human circadian rhythms.