Space mirrors could ruin astronomy — and your eyes
The dream of space mirror projects is to provide solar energy, day or night. Futurists have envisioned satellite mirrors reflecting sunlight onto Earth for over a century. Russian scientists experimented with the concept in the '90s with the Znamya project, aiming to put a large mirror in orbit and angle it to reflect sunlight onto specific areas for illumination or solar power generation.
Now, California-based Reflect Orbital wants to launch a test satellite, Eärendil-1, as a precursor to a fleet of up to 50,000 space mirrors. The 18-square-meter mirror satellite has been approved by the Federal Communications Commission (FCC) and will create a 5-kilometer-wide beam of light. This beam could be used for solar energy capture, boosting agricultural yields, or search and rescue operations during nighttime emergencies.
However, astronomers and experts have raised concerns. The satellite will be strikingly bright, with estimates placing the illumination as bright as Venus from outside the beam and four times as bright as the Moon within the beam. This could disrupt scientific observations and pose risks to public safety, including potential permanent eye damage for anyone using telescopes in the wrong place at the wrong time.
Roohi Dalal, deputy director for public policy of the American Astronomical Society (AAS), and Robert Massey, deputy executive director of the Royal Astronomical Society (RAS), warn that the plan could have disastrous effects on astronomy and harm humans and wildlife in affected areas. Light pollution, already a threat to human well-being and local ecosystems, could be exacerbated by space mirrors.
The issue is not just the brightness of the sky but the specific dangers to people and astronomy. The Hubble Space Telescope has already been affected by satellite streaks of white light trails, and the overall brightness of the sky from tens of thousands of reflective objects in orbit would be an existential threat to astronomy. The planned project could make it impossible to observe distant objects or spot Earth-threatening asteroids.
Reflect Orbital acknowledges the risk of eye damage from amateur astronomers using telescopes, but the FCC has declared these concerns outside its authority. The company hasn't shared plans to warn the public of its service's use, and there are concerns about flash blindness to drivers or pilots during satellite beam movement.
Critics argue that Reflect Orbital hasn't done its due diligence, and the approval of the test satellite by a House committee is seen as unlawful. The lack of regulation around potentially damaging satellite technologies is a growing concern, as more satellites are launched without oversight.
Reflect Orbital is working with the National Science Foundation (NSF) on a coordination agreement, but this is not the same as regulation. There are no federal laws limiting light pollution, and many US states have no such laws either. Protection of astronomical observations relies on the good intentions of private companies, who may prioritize profit over environmental or scientific concerns.
The scale of the problem is growing, with more satellites being launched, and these satellites are getting brighter due to lower altitudes and proposed orbital data centers. The IAU, along with Slovakia, has proposed banning space mirrors if strong oversight measures cannot be implemented to protect eye safety and astronomical research.
Astronomers question the tradeoff of tens of thousands of extremely bright satellites in the night sky, given the potential benefits. They argue that there are alternative avenues for generating solar power on Earth, such as better battery solutions and more solar panels, without damaging the night sky or harming nearby people or ecosystems.
The loss of the stars above us, a valued part of human heritage, is a concern. As Roohi Dalal notes, most people have not seen the Milky Way or a truly starry sky, and without these experiences, it's hard to understand what's being lost.
