Satellite mirror plans could disrupt sleep and ecosystems worldwide, scientists say | Satellites

Proposals to deploy reflective mirrors and up to a million additional satellites into low-Earth orbit could have far-reaching consequences for human health and ecosystems, leading sleep and circadian rhythm researchers said.

The presidents of four international scientific societies representing about 2,500 researchers from more than 30 countries are among those who have raised concerns in letters to the US Federal Communications Commission (FCC).

The regulator is studying plans by start-up Reflect Orbital to illuminate parts of the Earth at night using reflective satellites, as well as applications from SpaceX that could significantly increase the number of satellites in low Earth orbit.

“The proposed scale of orbital deployment would represent a significant alteration of the natural nocturnal light environment on a planetary scale,” said the presidents of the European Society for Biological Rhythms (EBRS), the Society for Biological Rhythms Research, the Japanese Society for Chronobiology and the Canadian Society for Chronobiology.

They said changing the light-dark cycle could disrupt biological clocks that regulate sleep and hormone secretion in humans and animals, the migration of nocturnal species, the seasonal cycles of plants and the rhythms of marine phytoplankton that underpin ocean food webs.

They urged regulators to conduct a comprehensive environmental review and set limits on satellite reflectivity and the cumulative brightness of the night sky. Professor Charalambos Kyriacou, a geneticist at the University of Leicester and chair of the EBRS, said: “We are saying: think before you take this step, because it could have global implications for things like food security. Plants need the night. You can’t just get rid of them.”

Reflect Orbital hopes to use satellites equipped with large reflective mirrors to redirect sunlight to areas approximately 5 to 6 km wide “on demand”, with adjustable brightness “from full moon to high noon”. The company says the system could extend solar power generation into the evening and provide lighting for construction projects, disaster response and agriculture, with lighting provided only in locations approved by local authorities.

Meanwhile, SpaceX has proposed launching up to 1 million satellites to create a giant solar-powered computer network in orbit, designed to run artificial intelligence workloads. The company says the system could reduce the power and cooling requirements of terrestrial data centers.

Ruskin Hartley, president and CEO of DarkSky International, a nonprofit focused on protecting natural night skies, who also wrote to the FCC, said: “While ideas such as mirrors on satellites beaming ‘sunlight on demand’ to Earth or satellite megaconstellations of up to 1 million meters for AI data centers may sound like science fiction, these proposals are very real.

He added: “Scientific studies have already shown that the existing number of satellites in orbit has increased the diffuse brightness of the night sky, or skyglow, by around 10%. »

Satellites have affected the night sky in two main ways, said Dr. Miroslav Kocifaj, of the Slovak Academy of Sciences in Bratislava. Individual satellites could leave marks on the telescope’s images, while sunlight reflected from satellites and debris illuminated the sky.

His modeling suggests that these objects already add between 3 and 8 microcandelas per square meter to the brightness of the night sky. By 2035, he predicts that this temperature could reach between 5 and 19 microcandelas, approaching the threshold set by astronomers for preserving naturally dark skies.

Although this extra brightness is still much less than that of moonlight, “what I can say with certainty is that the phenomenon is real, it is global and cannot be escaped by moving to a more distant location, and it will increase significantly over the next decade if current trends in satellite launches and debris generation continue,” Kocifaj said.

Professor Tami Martino, of the University of Guelph and president of the Canadian Society for Chronobiology, said that when it comes to impacts on life on Earth, “the real question is not comparing brightness to moonlight, but whether biological systems can detect the change.”

“Circadian systems are sensitive to light levels much lower than what humans typically perceive as bright,” Martino said. “If the night sky becomes permanently brighter, the consequences could ripple through ecosystems in ways we don’t yet fully understand.”

A separate letter from the presidents of the World Sleep Society, European Sleep Research Society, Sleep Health Foundation, Australasian Chronobiology Society and Australasian Chronobiology Society stated that “circadian disruption is not a mere inconvenience; it is a physiological mechanism leading to major adverse health consequences.”

“We do not take issue with space innovation,” the letter adds, arguing that changing the night sky must be treated with the same seriousness as other planetary-scale environmental changes, such as climate change and ocean acidification. “The alternation of light and dark is not a trivial background condition. It is one of the oldest organizing principles of life on Earth.”

Hartley said that as the number of satellites increases, fast-moving artificial objects could become a dominant feature of the night sky. “There might be times and places where satellites outnumber visible stars,” he said. Many birds and some insects navigated by the stars, and the human experience of the night sky could also be profoundly altered.

Reflect Orbital’s plans would also introduce a new form of light pollution with largely unstudied consequences, including potential risks to public safety, Hartley said. “As these beams move across the landscape, there is a risk of intense glare or blinding flashes, particularly if the systems malfunction or stray off target. These are exactly the types of risks that need to be carefully considered, which is why DarkSky is calling for a full environmental review before proposals like this move forward.”

Reflect Orbital declined to comment, while SpaceX did not respond to a request for comment.