MIT Technology Review is reporting that a new study suggests a company planning to beam sunlight from space to Earth could unintentionally brighten the night sky for many more people than intended. The U.S. company Reflect Orbital plans to launch a test satellite, Eärendil-1, later this year, which will deploy an 18-by-18-meter mirror in orbit. The company aims to test the feasibility of launching up to 50,000 larger satellites, each 54 by 54 meters, to reflect sunlight on demand. Reflect Orbital said its goal is to extend daylight hours for uses such as solar panel charging, emergency response and military activities. The Federal Communications Commission approved the launch in July.
Astronomers and environmental groups have expressed disbelief regarding the plan. Samantha Lawler, an astronomer at the University of Regina in Canada, said the plan is "incompatible with astronomy" and would not preserve dark skies.
Miroslav Kocifaj, an astronomer at the Slovak Academy of Sciences, and his colleagues calculated the broader effect on the night sky in a new paper accepted for publication in Astrophysical Journal Letters. They found that within a five-kilometer target area, a single Reflect Orbital satellite would appear about 40 times brighter than the full moon. As far as 14 kilometers from the beam's center, the satellite would still be as bright as the full moon. Combining the beams of 400 satellites, as Reflect Orbital eventually plans, would produce light as bright as 10,000 full moons within the five-kilometer area, or 2.4% as bright as the sun. Kocifaj and his colleagues calculated that even up to 80 kilometers away, this combined beam would be visible as "a glow above the horizon," altering the night sky for many beyond the intended illumination area. Kocifaj said deploying these mirrors would be "seriously damaging for astronomy and for the nighttime environment," with damage extending far beyond the target area. Olivier Hainaut, an astronomer at the European Southern Observatory in Germany, called the paper's results useful and comprehensive.
Reflect Orbital CEO Ben Nowack disagreed with Kocifaj’s findings, stating that "some assumptions are simply inaccurate" and that the company's safeguards, including exclusion zones, account for scattering. Nowack said Reflect Orbital has "engaged substantively with legitimate concerns" and that feedback has "informed our technology and operational plans." Kocifaj countered that Reflect Orbital has not provided data to support its claims, offering "no numbers, no description of the model, no assumptions, and no data."
In August, groups including DarkSky International and the American Bird Conservancy urged the FCC to review its approval of the Eärendil-1 satellite, citing potential negative consequences for aviation and wildlife, in addition to astronomy. The groups requested the FCC reverse its order and require a public-interest and National Environmental Policy Act review. Reflect Orbital itself noted in an FCC filing in March that observing Eärendil-1 with a telescope larger than 12 inches could be unsafe for human eyes, though it added that significant injury is unlikely because the satellites are not constantly bright.
Michelle Hanlon, a space lawyer at the University of Mississippi’s School of Law, said while there are "real benefits" to Reflect Orbital's plans, the "legal basis is less clear than the technology." Hanlon noted the FCC only has authority to authorize radio frequencies, not to license or regulate the solar reflector itself. She said Reflect Orbital would need national and local permission to reflect sunlight, and if beams spread as predicted, approvals might be needed in multiple jurisdictions, raising aviation-safety and cross-border questions. Lawler expressed sadness that astronomers must spend time on such calculations instead of astronomy.
Full Article: This company’s plans to deploy space mirrors could jeopardize the night sky for many