Satellite Constellations Are an Existential Threat for Astronomy

Satellite Constellations Are an Existential Threat for Astronomy

Astronomer Rachel Street recalls feeling scared after a recent planning meeting for Vera C. Rubin Observatory .. The flagship telescope is currently under construction in Chile. It will capture the entire sky every night with enough power to see a golfball at the distance of three nights. The Legacy Survey of Space and Time will be its primary project. It will map the galaxy and inventory objects in the solar systems. It will also explore mysterious flashes and blips throughout space and time. If the sky is filled with fake stars, the flagship telescope might not be able to achieve its goals. New swarms of satellite constellations, such as SpaceX’s Starlink, threaten to outshine the real celestial objects that capture astronomers’ interest–and that humans have admired and pondered for all of history.

” The more meetings I attend about it, where we explain its impact, the more I get scared about how astronomy will go forward,” Street, a scientist at Las Cumbres Observatory, says. Street felt a sense of unease as one astronomer spoke about increasing the telescope’s observation schedule. Her colleagues suggested that she make basic observations as soon as possible, before it’s too late. Street recalls, “That sent chills down my spine.”

As low-Earth orbit fills with telecommunications satellite constellations, astronomers are studying how to do their jobs when many cosmic objects will be all but obscured by the satellites’ glinting solar panels and radio bleeps. Recent reports from the Rubin Observatory team and from the U.S. Government Accountability Office paint a dire picture in in which astronomy–the first science–comes under direct threat. Astronomers warn that satellite constellations, if left unchecked will threaten not only the future of the Rubin Observatory (both its discovery potential and physical components) but also any future campaign to observe the universe in visible sunlight.

” It is somewhere in the range from very bad to terrible,” according to Jonathan McDowell, an Astrophysics researcher at Harvard-Smithsonian Center for Astrophysics. “A few thousand satellites is a nuisance, but hundreds of thousands is an existential threat for ground-based astronomy.” “A few thousand satellites is a nuisance, but hundreds of thousands is an existential threat to ground-based astronomy.”

Telescope project manager are currently rewriting scheduling software to avoid new satellite swarms. However, this already difficult task will become more difficult as the number spacecraft in low-Earth orbit continues to rise dramatically over the next few years. Astronomers are working on software that will eliminate bright satellite streaks in their all-sky images. This, too, will prove futile if the latest planned satellites make their way to orbit. They are so bright they threaten the basic electronics of telescope cameras. People who study phenomena such as near-Earth asteroids and colliding black holes worry that their work will be impeded, missing out on exciting discoveries and threatening cosmic threats. Astronomers are describing the satellite swarms with increasingly dire words. “The sky is falling, Chicken Little said. Anthony Tyson, chief scientist at Rubin Observatory and University of California Davis astronomer, says that instead of one acorn it is actually falling. “It is likely very high time to sound the alarm,” Tyson says. I might even say .”

almost too late.

Earth has had artificial satellites since Sputnik 1 launched in October 1957. At any given time, some 5,400 of them orbit Earth, with more than half of them owned by U.S. companies or agencies, according to a database maintained by the Union of Concerned Scientists. The database was last updated in January 2022, and many more Starlinks have launched since then, so those numbers are an undercount. Most satellites are in low-Earth orbit, which is considered any area less than 1,200 miles above the ground, and where satellites–including the International Space Station–make a full orbit every hour and a half or so.

Beginning in May 2019, SpaceX started populating that orbital plane with hundreds of its Starlink satellites, designed for broadcasting Internet and cell phone service around the globe. As of October, about 3,450 of the total satellites orbiting Earth–more than half–are Starlinks, according to McDowell’s tracking efforts. Because they are separated in patterns that allow them to work together, the spacecraft are launched in groups. Astronomy is challenged by both the number of satellites and their brightness. They can be seen shining across the twilight sky as a tiny, dazzling train. They appear as bright streaks or light in telescope digital cameras. These bright streaks block stars and astronomical objects, as well as overexposing the entire field of vision. Tyson states, “It’s almost like you’re driving down the highway and looking out through your windshield at an oncoming car with brights on.” “You lose a lot information–not only at the position of those lights, but all around, and your eyes may be too .”


The $473 million Rubin Observatory is uniquely threatened among ground-based astronomy projects. The telescope is scheduled for first light in 2024, and by then tens of thousands of small-to-medium satellites, including Starlinks and others, could be orbiting Earth. The observatory’s planned Legacy Survey of Space and Time will use an 8.4-meter telescope combined with a 3.2-gigapixel digital camera, the largest ever built, to capture 1,000 images of the sky every night for a decade. Each image will cover 9.6 square degrees of sky, which is about 40 times the area of the full moon. The telescope is designed to detect new, potentially dangerous near-Earth objects as well as transient events such as supernovae, and even things no one has yet thought of, Tyson says. These observations could be “significantly diminished” by the alarming pace of satellite deployments, according a Rubin Observatory analysis. It was primarily written and posted in September .

Another report, prepared by the U.S. Government Accountability Office watchdog agency and sent to Congress September 29, found that the satellite constellations could harm astronomy and cause environmental impacts as they fall back through Earth’s atmosphere. The GAO stated that “as more satellites become deployed into [lower-Earth orbit], almost all facets optical astronomy could be negatively affected.” The agency requested further research to determine the full impact of satellite constellations on astronomical research and new policies to eventually create regulations and standards. Many astronomers are concerned that such rules will not be developed soon enough or be strict enough to save ground-based Astronomy.

SpaceX is the most prominent provider of satellite swarms. It is also the only company to collaborate with astronomers to dim its satellites. The company has launched “DarkSat,” a light-absorbing darker satellite, as well as anti-reflective coatings for solar panels. SpaceX did not respond when asked. Between Starlink and other companies, such as British satellite provider OneWeb and a Chinese company called Galaxy Space, more than 4,000 satellites designed for constellation-like networked coverage are now in orbit. According to permits filed with the U.S. Federal Communications Commission and the International Telecommunications Union (the world’s two leading telecommunications agencies), a combined 431,713 satellites in 16 constellations are planned to launch in the coming years.

The satellite companies point out that nearly one third of the world’s population–some 2.9 billion people, according to a 2021 ITU report–have still never used the Internet. Satellite communications satellite constellations could change this. But light from the Starlink constellation alone will add streaks to at least 30 percent of images made from the Rubin Observatory. If 400,000 satellites make it to orbit, every image taken in the early evening will have a streak. OneWeb will orbit at a higher altitude than other constellations so it will be visible throughout the night. OneWeb did not respond to a request to comment. Even if software programs could erase satellites to save pixels around bright streaks, data errors in light-detecting chips will still be a problem. “Operators of satellites in [low-Earth orbit] will present a significant threat to the main mission of LSST: discovery of the unexpected,” the Rubin Observatory report concludes.

Astronomers, as well as one private company, are developing software that can remove some satellite streaks or change the location of the telescope to avoid them. It’s difficult to do because satellites move and can appear differently in different color filters. Meredith Rawls of the University of Washington works on a team that will send out alerts for new phenomena Rubin Observatory catches in the night sky, which could reach 10 million alerts per night. She says that software is supposed to filter them and contact the global community of astronomy only for meaningful events like supernovae or asteroids.

” With the streaks, it’s possible to get strange blip-blip patterns. Our software will flag this as a potential object, or a supernova. She says it’s a satellite. “This is going [to cause] more false positives that we would like to have, and then it becomes difficult to guess how many. Is it going to be five a night, or 500 a night? We don’t know .”


Rawls worked with a project that fed satellite locations to the observatory’s scheduler algorithm. They found that if the telescope operators knew where the satellites were, the algorithm could point the telescope elsewhere to avoid them. Rawls and his colleagues discovered that this was so difficult that it could have a detrimental effect on the entire pipeline of observations. They’re planning to submit their findings to the Astrophysical Journal Letters.

Meg Schwamb, an astrophysicist at Queen’s University Belfast, was the astronomer who proposed doing the Rubin Observatory’s twilight studies early in its 10-year lifetime–thus giving Street the chills. Twilight is when near Earth asteroids can be easily detected, and when the Rubin Observatory may detect many more. The Chelyabinsk meteor, for instance, which shocked everyone when it exploded over Russia in 2013, arrived from a similar direction as the sun and is just the sort of object the Rubin Observatory was designed to catch. Partially sunlit observations will prove more difficult because the solar panels of satellite constellations will be illuminated at this time.

” I never thought that, as an astronomer. We don’t know what our satellite field will look like. Astronomers are more likely to extend the observatories’ lives and come up with new campaigns in the later years. This order should be reversed, so that basic science is done before the observatory is blinded. This is contrary to how scientists plan their work and their entire careers. Schwamb likens satellite constellations to orbital ads and says that humanity must figure out how to control them. She said, “If it weren’t Starlink but Coca-Cola would we be okay with that?” “This is a deeper cultural issue, too. Should Elon Musk have control over what people see in night sky ?”


Astronomers acknowledge SpaceX tried many methods to darken their satellites. However, the spacecraft remain visible and other providers don’t use such mitigation strategies. Starlink satellites made by other companies and older Starlink satellites are larger and brighter. A company called AST SpaceMobile launched a prototype, called BlueWalker 3, on September 10; it could soon become the brightest object in the night sky besides the moon. It contains a 693-square-foot (64.4-square-meter) phased array of antennas, which can communicate directly with cellphones on Earth, and which may outshine even Jupiter when BlueWalker 3 fully unfurls on November 10. AST SpaceMobile aims to launch 168 even larger satellites, called BlueBirds, in the next few years. According to a company spokesperson, BlueWalker 3 will be used to help engineers assess the satellite’s materials as well as judge its brightness. NASA and industry experts are also being involved in the company’s efforts to reduce brightness concerns. AST SpaceMobile is looking at anti-reflective materials as well as changes to operations to make satellites dimmer.

Although there will be fewer BlueBird satellites that other constellations, they could pose a different problem than smaller satellites. Some telescopes may not be able to see very bright BlueBirds because telescope cameras are made to see bright objects such as the moon and planets. It will be difficult to escape hundreds of them. A bright satellite could also pass through a digital camera’s long exposure, causing damage to the sensitive electronics.

” It is obvious that technology is here. McDowell states that you could destroy the night sky if you wanted. “Whether or not this happens will depend on the details of these business cases and the regulatory environment. Therefore we should talk about whether that’s acceptable.”

However, the pace of satellite construction is far too slow for astronomical research and regulation, according to many astronomers. “Everyone is becoming more alarmed. Aparna Venkatesan (University of San Francisco cosmologist) says that we aren’t sure where to place our shoulders to the wheel because there are so many. She also studies cultural astronomy. “The momentum and power are very one-sided.” Astronomers tend not to move quickly and carefully. They also organize conferences and meetings.

Many astronomers believe that new rules from FCC, which regulates satellite communications in the U.S.A., are not enough. Astronomers have been working closely with the United Nations Committee for the Peaceful Use of Outer Space, which held a meeting this spring on satellite swarms. However, the process is slow. McDowell states that if COPUOS considers protecting night sky as part of its mission, then member countries may be encouraged by McDowell to use their national regulatory frameworks to set rules about how many brightly launched satellites can be launched and where they can go.

Many astronomers hope that their field will be saved if satellite constellation operators pull back because not enough people sign-up for their internet services. The companies could work together to slow down their launches to prevent space debris. This would limit everyone’s access into space. The hard truth is that no one can stop the steady launch of satellite constellations with their sun-reflecting solar panel arrays.

Astronomers even resort to a kind of gallows humor regarding the future years. A satellite loss occurred in February when Starlink satellites were placed in low orbit to prepare for their permanent altitudes. A solar flare traveled to Earth and sparked a plasma storm in the uppermost layers of the atmosphere, causing excess atmospheric drag and radio interference; 40 satellites tumbled back down and burned up. When asked what astronomers could do to prepare for the increasing number of satellites, many joked that they would “wait for solar maximum”, when the sun’s activity will increase and cause more such storms.

Other than software patches or a geomagnetic storm, physical modifications to the spacecraft can be used to prevent complete viewfinder contamination. Software is more able to remove dimming objects, and satellites at lower orbital altitudes will need to travel faster so they don’t drop to Earth. This would allow them to zip out of the way quicker. Rubin Observatory team members hope private companies will build more reflective satellites and place them in lower orbits. However, these decisions would be up-to the companies. There are no laws that require them to do so. Rawls states that companies should reach out to astronomers and explain their plans and potential impacts to astronomy. “Kind of like in a city, when they want to build a new bike lane, it takes three years because they have to have 700 meetings with stakeholders. She adds that she would love to have that space. “But in some aspects, everyone who looks up is a stakeholder. And that makes it a real challenge.”

Astronomers do not have to agree on the issue. Members of the community have expressed different levels of concern and awareness about satellite constellations. McDowell states that the amount of fear is dependent on how much one knows about satellites and what interests one has, as well as which observatories are affected. “If your science is like that of the Rubin Observatory, then the sky is likely falling. He said that narrow-field spectroscopy, which studies starlight, is not as obvious as the sky falling.

The alarm is centered on the near future and although many are concerned, no one knows how serious it will become or how long it will last. It could be a glimpse of the future for the cosmos as a whole. Cosmologists like Tyson debate the eventual fate of the universe. One possible scenario is a “big freezer,” where all matter is pushed apart so far that stars will go extinct. The universe will continue to expand, driven by dark energy, and eventually, the larger cosmos will become inaccessible from Earth. If humans are still alive at that point, they will have no choice but to abandon the starry skies as a way of understanding the universe and themselves. Tyson spoke of the satellite constellations as “a version of that.” “Very soon the sky will be visually dominated rather than the stars,” Tyson said of the satellite constellations. This will hold true regardless of whether you live in a country or a city. The future is one in which the sky is twinkling constantly, everywhere, from all of these satellites.”



    Rebecca Boyle is an award-winning freelance journalist in Colorado. Her forthcoming book Walking with the Moon: Uncovering the Secrets It Holds to Our Past and Our

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