5.12.2025
Planned megaconstellations would contaminate the view of the cosmos of four orbiting telescopes
Many of the images taken by the Hubble Space Telescope will be blemished by satellite trails if plans to launch megaconstellations succeed.Credit: NASA/Science Photo Library
Even telescopes far above Earth can’t avoid the contamination caused by commercial satellites.
Blurry streaks of light created by fast-moving artificial satellites are already known to mar images taken by ground-based observatories. Today, researchers report1 in Nature that space-based telescopes will not escape such interference as fleets of private satellites proliferate. The researchers found that in the next decade, satellite trails could taint roughly 96% of the images taken by some space-based telescopes, and a single image could contain as many as 92 streaks.
The findings are “truly frightening”, says Patrick Seitzer, an astronomer at the University of Michigan in Ann Arbor, who was not involved in the work. “This is a very important study for the future of space-based astronomy.”
Tight space
Around 15,000 satellites launched by various companies currently orbit Earth, and several firms plan to launch groups of thousands more, forming ‘megaconstellations’ that will be used for telecommunications (see ‘Rocketing upwards’). For example, aerospace company SpaceX plans to grow its existing Starlink fleet to some 34,000 satellites.
Source: Ref. 1
To work out what effects these satellites will have, Alejandro Borlaff, an astrophysicist at NASA’s Ames Research Center in Moffett Field, California, and his team conducted computer simulations of the view from four low-Earth-orbit telescopes, which either currently occupy space or are soon planned to. They include the iconic Hubble Space Telescope; NASA’s SPHEREx Observatory, which launched in March; China’s Xuntian Space Telescope, set to launch as early as next year; and the European Space Agency’s ARRAKIHS mission, set to launch in 2030.
The researchers simulated roughly 18 months of observations, taking faux space pictures with various numbers of satellites in orbit (see ‘Obstructed vision’). They found that if 560,000 satellites are in orbit — the number that is currently planned for launch — their trails will contaminate from 40% to more than 96% of each telescope’s images. And with 1 million satellites in orbit, the number of streaks per image reaches 165 for some observatories. At that rate, “we will have fewer discoveries, less interesting images and, in general, less knowledge”, says Borlaff. SpaceX did not respond to a request for comment about the effects of its constellation.
The most concerning impact he foresees is that the satellites could easily be confused with Earth-threatening asteroids. “And if your images look like they’re filled with asteroids, it’s very possible that you’ll miss a real one,” Borlaff says. He also worries that satellite streaks might make it more difficult to detect rare, fleeting phenomena such as powerful explosions called γ-ray bursts.
Light reflected from telecommunication satellites leaves streaks on a simulated image by ARRAKIHS, an orbiting telescope scheduled to launch in 2030. Credit: NASA Ames/A. S. Borlaff, P. M. Marcum, S. B. Howell
Quelle: nature
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NASA study shows how satellite 'light pollution' hinders space telescopes
An exponential increase in the number of satellites placed in low-Earth orbit has brought advances in telecommunications including broadband access in rural and remote areas worldwide. It also has caused a surge in light pollution in space that imperils the work done by orbiting astronomical observatories.
A new NASA-led study focusing on four space telescopes - two currently operational and two planned - estimates that a large percentage of images obtained by these observatories over the next decade could be tainted by light emitted or reflected by satellites sharing their low-Earth orbit.
The researchers calculated that about 40% of images taken by NASA's Hubble Space Telescope and about 96% of those taken by the U.S. space agency's SPHEREx observatory could be contaminated by light from satellites. They also calculated that about 96% of images from the European Space Agency's planned ARRAKIHS observatory and China's planned Xuntian telescope could be similarly affected.
Hubble would be less affected due to its narrow field of view, the researchers said.
Orbiting telescopes are a vital part of space exploration. They can observe a wider range of the electromagnetic spectrum than ground-based telescopes, and the lack of atmospheric interference lets them get sharper images of the cosmos, enabling direct imaging of distant galaxies or of planets beyond our solar system.
"While until now most light pollution came from cities and vehicles, the rise of telecommunication satellite constellations is rapidly starting to affect astronomical observatories worldwide," said astronomer Alejandro Borlaff of NASA's Ames Research Center in California, lead author of the study published in the journal Nature, opens new tab.
"As telescopes stare at the universe attempting to unveil distant galaxies, planets and asteroids, satellites sometimes cross in front of their cameras, leaving bright traces of light that erase the dim signal that we receive from the cosmos. This was a known problem for ground-based telescopes. But until now, space telescopes - much more expensive and placed in apparently pristine vantage points of view in space - were thought to be almost free of human-made light pollution," Borlaff said
In 2019, there were roughly 2,000 satellites in low-Earth orbit. The number now is around 15,000. Borlaff said that proposals from industry foresee around 560,000 satellites in low-Earth orbit in the coming decade.
"To give an idea of how much this number increased recently, we have launched more satellites to low-Earth orbit in the last four years - 2021 to 2025 - than in the previous seven decades of space flight combined," Borlaff said.
The researchers used information from satellite operators to simulate the orbital layers of each satellite constellation - from SpaceX's Starlink, China's Guowang and Amazon (AMZN.O), opens new tab, among others. They then considered specific properties of the telescopes such as orbiting altitude, trajectory, field of view and other factors.
"Once we had the simulated telescopes observing our simulated universe, we only needed to count the number of times that the satellites crossed - or 'photo-bombed' - our observatories, and how bright they were at the moment of the event," Borlaff said.
Satellites reflect and emit multiple types of light.
"They directly reflect light from the sun with their solar panels, but also reflect light from the moon and the Earth, which is very intensely bright from low-Earth orbit. In addition to optical light, satellites also emit infrared radiation generated from the temperature of their components, as well as reflecting radio wavelengths from both the Earth and the antennas themselves," Borlaff said.
The researchers said one way to address the problem would be to deploy satellites at orbits lower than where the telescopes operate.
Some telescopes placed at more distant orbits are better shielded from light pollution. The study, for instance, did not look at the effects of the satellites on NASA's James Webb Space Telescope, the European Space Agency's Euclid observatory or NASA's planned Nancy Grace Roman Space Telescope.
Their orbits are much further from Earth than the telecommunications satellites.
"For that reason, they won't likely be affected by this type of contamination, for now," Borlaff said.
These unaffected telescopes provide only a fraction of total astronomical observations, however.
"They are only used for very particular scientific objectives, and have very limited operational time," Borlaff said.
Quelle: Reuters
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