The sudden increase in satellite launches is making it increasingly difficult for Hubble and other Earth-orbiting telescopes to capture ancient images. Satellite trails could spoil about 40 percent of the images taken by Hubble and 96 percent of the images taken by three other telescopes over the next decade, according to a study by NASA researchers published today in the journal Nature. Nature,
They warn that this could jeopardize scientists’ ability to identify asteroids of concern or discover new planets. Without efforts to limit light pollution from new megaconstellations of satellites our view of space becomes blurry.
The scale of the problem is astonishing
“My career has been focused on trying to make telescopes see better… make telescopes more sensitive, more accurate, try to get better images,” says Alejandro Borlaf, a NASA research scientist and lead author of the study. “For the first time, we found something that may actually get worse in the future.”
The scale of the problem is astonishing. Cheaper launch costs and the proliferation of telecommunications satellites like Starlink have opened up a host of new challenges in space. Satellite trails, which look like streaks of light, were already found in 4.3 percent of the images taken by Hubble between 2018 and 2021. According to the European Space Agency, the number of satellites orbiting Earth has increased from 5,000 in 2019 to more than 15,800 today. This number could reach 560,000 if currently planned satellite launches proceed over the next 10 years.
Borloff and his colleagues pursued the idea that there would likely be four telescopes after all those launches. With so much crowding in space, they estimate that the Hubble telescope may inadvertently capture an average of 2.14 satellites per exposure. One of the other telescopes involved in the study, the Chinese Space Station Telescope Xuntian, which is expected to launch next year, can see an average of 92 satellites per exposure. Hubble is less likely to capture more satellites in its images due to its narrow field of view. Fortunately, other powerful telescopes, including James Webb, orbit far enough from Earth to avoid light contamination from satellites.
The matter goes even further by accidentally including a satellite (or several) among the views of swirling nebulae, stars and distant planets captured by these telescopes. Satellites reflect light from the Sun, Moon or Earth, which can be so bright as to obscure details that might otherwise be captured in an image if it were not for light pollution. Borloff explains that researchers may not be able to detect changes in a star’s brightness that might indicate there is an exoplanet. “You’ll lose that information because a satellite passed in front of you.”
Now is the time to find a solution, he says, before there are so many satellites in orbit. Efforts to design darker, less reflective satellites have created new problems as they become hotter and emit more infrared light as a result. Researchers have also tried to strategize about taking pictures at times and places where satellites are less likely to cross their path, an effort that is difficult to accomplish when there are more crowds. The satellites will require more coordination on the ground with the companies and governments launching them, perhaps by placing them in lower orbits than the telescopes, to avoid obstructing their view or regulating where they can be deployed.
“There has to be an optimal way to house constellations and space telescopes… so that we can co-exist in a sustainable way,” says Borloff.
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