Increasing number of satellites has the potential to impact Grand Canyon
GRAND CANYON, Ariz. – While the general consensus among professional astronomers is that Grand Canyon National Park is a model for reducing light pollution on public lands; its night skies will continue to be impacted by distant surrounding cities such as Las Vegas and Phoenix. Unfortunately, some of that pollution will also come from the very skies overhead of the park’s nearly 6 million annual visitors, according to Dr. John Barentine.
Sunlight reflected off of everything orbiting the planet has made the night sky 10 percent brighter over natural levels, according to research that Barentine co-authored last year in the Monthly Notices of the Royal Astronomical Society. It’s a threshold that threatens boundaries set by the International Astronomical Union for when a location is considered to be light polluted.
“We’re not only worried about the little discrete points of light (satellites going across the horizon) in the night sky, but now we’re worried that if the satellites basically grind themselves up into dust, that will make the night sky itself brighter and therefore have an impact on the ability to see the night sky,” Barentine said.
Since 2019, the number of functional satellites in orbit has more than doubled and it’s going to grow vastly more, with possibly up to 100,000 operational satellites within the next eight years – that is 25 times the current level, according to a 2020 report from The Verge. In large part this increase is from the launch of satellite mega-constellations such as SpaceX’s Starlink, according to Barentine.
“We’ve been watching this now for almost three years,” he said. “When SpaceX launched the first of its Starlink constellation of satellites into orbit, with the intent of eventually deploying about 40,000 of them into Low Earth orbit so they’re a bit below the International Space Station as a point of reference.”
Those satellites spend part of their time in direct illumination by sunlight, even though an observer on the Earth is in darkness and so we see them as bright objects moving in the sky. That has an impact on professional astronomers, casual stargazers.
There’s cultural and even religious implications as well, especially among Indigenous people who use the night sky in their cultural practice and remaking it with all of these satellites is raising alarm, according to Barentine.
“The injection of thousands of metallic, highly reflective objects into our atmosphere is kindred to environmental degradation because it is changing our sky and we don’t yet know if we can reverse it,” Indigenous research associate, Karlie Alinta Noon said in an October report from Vice.
With the sky becoming increasingly crowded the probability of collisions among satellites or other objects also increases, which can create a positive feedback loop, generating further debris.
“You could get a situation where it just runs away on you,” Barentine said. “The rate at which you are generating these little pieces of debris becomes exponential, that raises further collision risk. Our research on this suggests, if you were to massively increase the number of these small debris, objects that are in orbit, that the collective reflection of sunlight from all of those objects actually raised the brightness of the night sky itself, akin to … the skyglow from the cities, makes it difficult to see the stars.”
The study implies the night sky will brighten proportionally as new satellites are launched. Satellite operators such as SpaceX and OneWeb have taken some voluntary measures to dampen their impact through design changes and changes in their orbits, according to Barentine.
“They have yet to reduce their visibility below that of the unaided eye which means particularly in dark sky sites such as the Grand Canyon,” Executive Director of the International Dark-Sky Association, Ruskin Hartley said. “When you look up at night, you’re much more likely to see satellites streaking overhead. Particularly during the dawn and dusk hours when they’re not in the shadow of the Earth.”
SpaceX has applied darkening material to the surface of some of its satellites to reduce the amount of reflected sunlight it has the effect of making the satellites fainter. But darkening also heats the craft up because it absorbs heat from the sun very efficiently in orbit and heat can pose a danger to onboard equipment.
“They also tried maneuvers where they roll the spacecraft as it’s moving up to its final location to limit the amount of surface that can reflect sunlight,” Barentine said. “(But) they’re still too bright, according to their own, self-imposed threshold.”
For the International Dark-Sky Association there’s a genuine threat to naturally dark places such as Grand Canyon National Park from satellites.
“There has to be balance with the need to bring connectivity to rural communities, particularly those that have traditionally been underserved such as the Navajo Nation,” Hartley said. “But there hasn’t been any meaningful environmental review of these launches and deployments and there hasn’t been any meaningful consultation with the impacted parties.”
More information about dark skies is available from the International Dark-Sky Association.