Bright satellites in the thousands can affect future discoveries of space

This clutter of the sky includes satellite constellations currently orbiting the Earth, such as SpaceX’s Starlink satellites, and thousands of potential future satellite constellations that may be launched in the future.

It is estimated that 107,000 orbit satellites will be launched in the coming decades.

The astronomical community was concerned about these man-made constellations following the first launch of SpaceX by 60 Starlink communications satellites on a single rocket in May 2019. More launches have taken place since then, and future launches are planned.

Prior to the launch, SpaceX had suggested that the satellites would be barely visible, according to the American Astronomical Society. Within days of launch, it was clear to astronomers and astronomers that the metal satellites, which reflected the sun’s light, appeared as bright as astronomical constellations in the night sky.

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In fact, the formation of satellites orbiting the Earth and its unique “appearance of pearls” actually led to people reporting UFO sightings because they did not realize that satellites could be so visible in our night sky. , according to the AAS.

One of the purposes of these constellations of LEOsats, as low-Earth satellites are known, is to help deliver communications in remote and underserved areas.

“I think it’s commendable and very impressive engineering to spread the information and opportunities that are possible through Internet access,” Megan Donahue, president of the American Astronomical Society, said in a statement. “But I, like many astronomers, am very worried about the future of these new light satellites.”

Astronomers estimate that these “swarms” of satellite could become the dominant luminous objects in our sky, instead of stars. That disruption could change how astronomers, professional and amateur, see the night sky, they said.

At the end of June, NOIRLab of the National Science Foundation and the American Astronomical Society organized the Satellite Constellations 1 workshop to bring the astronomy community together with satellite operators. The agenda was to understand and possibly reduce the impact of satellites on astronomy.

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This forum gave astronomers time to observe the satellite constellations launched by SpaceX and OneWeb over the last year, and perform simulations to understand the effects as more constellations are launched.

The SATCON1 virtual workshop allowed more than 250 scientists, engineers and commercial satellite operators, including those of SpaceX, to collaborate.

Team members of the workshop shared findings and recommendations, including those for satellite operators and observatories, on Tuesday when the report was released and submitted to the National Science Foundation. The NSF funds many of the large ground telescopes available to researchers for observations across the United States.

Overall, the impact on astronomical research, including astronomy based on visible and infrared light, varies from negligible to extreme, the report’s authors concluded.

How astronomy will change

These satellite constellations were no problem 10 years ago when the National Research Council of the National Academy of Sciences released its Astro2010 decadal survey on astronomy and astrophysics. The survey, which identifies priorities in these areas and proposes new ones for the decade, is released every 10 years and helps U.S. government agencies determine funding.

The top recommendation of the 2010 survey was funding and development of the Vera C. Rubin Observatory. The observatory, located in Chile but led by America’s National Science Foundation, will begin scientific operations in 2022. It is designed to produce the deepest, broadest picture of the universe as it conducts a 10-year survey of the sky. The observatory’s broad field of view could help answer questions about the universe and detect faint celestial objects.
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But these satellite constellations will affect the view of the observatory.

“The Rubin Observatory and the giant 30-meter telescopes that will go online in the coming decades will substantially improve the understanding of the cosmos’s humans,” said Jeff Hall, SATCON1 co-chair of Lowell Observatory and chair of the AAS Commission on Light Pollution, Radio Interference, and Space Debris, in a statement. “For reasons of cost, maintenance and instrumentation, such facilities cannot be operated from space. Based astronomy is, and will be, vital and relevant.”

The first finding of the report is that these satellite constellations will have the greatest impact on observation programs occurring at dusk, when the sun is below the horizon for observations on ground. But the sun still reaches the satellites that remain illuminated hundreds of miles above.

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The programs that depend on twilight observations include searching for near-Earth objects such as asteroids and comets, objects in the outer solar system and the fleeting signatures of sources of gravitational wave.

One recommendation in the report to limit this impact is to keep satellites at 373 miles or less to limit this interference. However, some future satellites will, like a constellation planned by OneWeb, orbit about 750 kilometers above the Earth and directly in the interference zone. These satellites could be visible all night long in the summer and much of the night in other seasons “and will have negative effects on almost all observation programs,” according to the report.

A dark sky is full of potential. The Hubble Space Telescope observed a seemingly low part of the sky in 1995 for 10 days. This small target reveals the Hubble Deep Field, filled with thousands of galaxies that retreat to the early years of the universe.
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“Dark skies contain many secrets, and today’s flag-based basics are slowly being revealed,” the authors wrote in the report.

The light orbits surrounding these constellations will disrupt the detection of exoplanets orbiting cool M dwarf stars, which some astronomers believe may be habitable. It can also interfere with the discovery of new objects or phenomena that have not yet been foreseen.

What could change

The second finding of the report contains six ways to limit the effects on astronomy. The first is impractical and unlikely: “start less or no LEOsats.” But, the authors wrote, “this is the only identified option that can achieve zero astronomical impact.”

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The other suggestions are more practical. They include deploying satellites no higher than 600 kilometers or 373 miles above the earth, obscuring the reflecting surfaces of the satellites or using sunshades to shade them and orient the satellites so that they reflect less sunlight.

The authors also suggested minimizing or eliminating satellite traces in astronomical images through software and sharing accurate orbital information regarding satellite position so that scientists could avoid them.

These, and other specific recommendations aimed at collaborating observatories and satellite operators, include immediate action points such as long-term strategy.

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“SpaceX has carried out a series of development efforts exploring possible mitigation strategies,” according to the report, including those to darken the satellites.

A future SATCON2 workshop that will focus more on policy and regulatory areas is planned for the first half of 2021.

“I hope that the collegiality and spirit of partnership between astronomers and commercial satellite operators will expand to include more members of both communities and that it will continue to prove useful and productive,” NOIRLab director Patrick McCarthy said in a statement.

“I also hope that the findings and recommendations in the SATCON1 report will serve as guidelines for observatories and satellite companies, as we work towards a more detailed understanding of the effects and mitigations, and we learn to share the sky, one of the precious treasures of nature. “