Reflections caused by the growing number of satellites in Earth’s orbit could compromise more than 95% of images captured by some space telescopes in the next decade, according to a NASA-led study.
Reflected light appears as trails, known as satellite trails. This phenomenon has already been observed in images captured by NASA’s Hubble Space Telescope. The situation is only expected to worsen with the accumulation of more satellites in orbit, according to the researchers.
The study, published in the journal Nature on Wednesday, predicts that other telescopes will also show images with satellite trails, including NASA’s SPHEREx, the European Space Agency’s ARRAKIHS, and China’s Xuntian Space Telescope. SPHEREx was launched this year, while ARRAKIHS and Xuntian have not yet been launched.
A valuable image could be obtained, for example, “by observing a galaxy and suddenly a very distant star explodes,” says Alejandro S. Borlaff, the study’s lead author and a NASA scientist. But “if a satellite is crossing the field of view, that information will be lost forever,” he told Nature in a podcast interview.
The problem has worsened in recent years: more satellites have been launched in the last four years “than in the previous 70 years of spaceflight combined,” Borlaff stated.
More than 10,000 active satellites are in orbit as of December 1, according to data from Jonathan McDowell, astrophysicist at the Harvard-Smithsonian Center for Astrophysics. Most of them belong to SpaceX—the company has more than 7,800 Starlink satellites in orbit.
The International Telecommunication Union (ITU), which oversees proposed satellite applications in space, states that there are “thousands of other satellites” planned for launch into orbit.
Between 2018 and 2021, when there were fewer satellites in orbit, about 4% of Hubble Space Telescope images showed satellite light trails, according to another study published in Nature Astronomy in 2023.
But Borlaff and others predict that this number could increase, with at least one in every three images captured by the Hubble Space Telescope showing a light trail. “That’s an impressive number. It’s really very high compared to what we see today,” Borlaff told Nature’s podcast. “In the case of the SPHEREx, ARRAKIHS, and Xuntian telescopes, we expect about 96% of images to be contaminated in some way.”
Borlaff’s study and others show that the increase in satellites could also impact images captured by ground-based telescopes.
The scientific community and astronomers have long been concerned about satellite trails affecting images.
The American Astronomical Society (AAS) has warned that the increase in satellites in low Earth orbit could cause collisions with space telescopes and create glints and light trails in telescopic images.
“We will continue to facilitate collaborative work with federal agencies and the satellite industry to fully understand and minimize the impacts of large satellite constellations on astronomy,” said Roohi Dalal, AAS deputy director of public policy, in a statement to NPR on Sunday.
NPR contacted SpaceX for comment on Saturday but received no response. SpaceX has previously stated that it is taking steps to reduce light emitted by its satellites, including tests with darker coatings, addition of sunshades to block sunlight, and adjustments to their orbits to reflect less sunlight.
The International Telecommunication Union (ITU) has also expressed concern about the rapid increase in satellites in space. In a recent report, the UN agency stated that this “poses significant risks to space sustainability, including collisions and debris generation, threatening the long-term viability of orbital resources.” The ITU has advocated for stricter international rules on the number of satellites in space and better management of satellite networks.
Source: npr.org by Chandelis Duster