Hubble Telescope finds itself under threat from SpaceX satellites – 05/03/2023 – Science

The Hubble Space Telescope, known for capturing awe-inspiring images of the cosmos while advancing the field of astronomy, is under threat.

Private companies have launched thousands of satellites into space that are bombarding the telescope with light, producing long bright, curved streaks that can be impossible to remove. And the problem only gets worse.

A study, published last Thursday (2) in the journal Nature Astronomy, reveals an increase in the amount of images recorded by Hubble that were spoiled by passing satellites. And the data only go up to 2021.

Thousands of satellites have since been launched by SpaceX and other companies, and many more are expected to enter orbit in the coming years, affecting Hubble and potentially other space telescopes.

“We’re going to live with this problem. And astronomy will be impacted,” said Jonathan McDowell, an astronomer at the Harvard-Smithsonian Center for Astrophysics who was not involved in the study. “Some experiments cannot be done. There will be science that will cost significantly more. There will be things we won’t see.”

The legacy of the Hubble Space Telescope is immeasurable. Because of the observatory, we now know, for example, that the universe is 13.8 billion years old, that most galaxies contain a supermassive black hole at their center, and that stars form in violent processes. Hubble images – including the beautiful clouds of gas and dust in the “pillars of creation” and the view of nearly 10,000 galaxies in the “Hubble Ultra Deep Field” – are always awe-inspiring.

But the number of orbiting satellites has increased significantly since Hubble was launched in 1990, and it now observes the cosmos through a field of satellites.

In May 2019, SpaceX launched its first batch of Starlink satellites, designed to beam internet signals around the world. Soon after, there was a backlash from astronomers concerned that Starlink’s streaks would threaten several campaigns to observe the universe from telescopes on Earth.

In response, Elon Musk, founder and CEO of SpaceX, suggested that astronomers work around the problem by taking the telescopes into orbit.

But Hubble, which lives in low Earth orbit about 536 km above the planet’s surface, is actually less than 16 km below most Starlink satellites. This means that the observatory and other orbiting space telescopes still face interference from satellite constellations. “Not only do you have to get your telescopes out into space, you have to get them above all other traffic,” McDowell said.

“I think we’re going to be forced to do that for decades to come,” he said. But it’s not yet possible for current telescopes in low Earth orbit or the spacecraft governments are building to launch in the next few years.

To quantify the effect of satellite constellations on Hubble, Sandor Kruk, an astronomer at the Max Planck Institute for Extraterrestrial Physics in Germany, and his colleagues analyzed an archive of images taken from 2002 to 2021.

They had the help of hundreds of citizen scientists who pored over the images to mark the ones with clear satellite streaks. This dataset was then used as training for a machine learning algorithm that analyzed more than 100,000 individual Hubble photos.

Their results show that the chance of seeing a satellite in a Hubble image from 2009 to 2020 is only 3.7%. But the chance of seeing one in 2021 is 5.9% – an increase that, according to them, corresponds to Starlink. As of the date of analysis, there were 1,562 Starlink satellites in orbit. Another company, OneWeb, had installed 320 satellites.

Mark McCaughrean, an astronomer at the European Space Agency and co-author of the new study, is confident in his analysis, but notes that this is only a minor issue at the moment. Normally, Hubble takes several images that are stacked on top of each other, a technique that erases all satellites.

And NASA agrees. “While these analyzes may show a gradual increase in satellite contrails detected over time, most of these streaks are quickly removed using standard data reduction techniques, and most affected imagery can still be useful,” said a spokesperson. voice compared to the most recent study. “Currently, satellite contrails do not pose a significant threat to Hubble’s scientific efficiency and data analysis.”

That threat is greatest when Hubble surveys a large swath of the sky. So he manages to take just one or two shots before redirecting his camera. If a satellite photobombs one of these images, it may have to be discarded.

A SpaceX spokesman declined to comment on the new study, but pointed to the company’s past efforts to mitigate Starlink’s effects. The company has tried several methods to dim its satellites, including a mirrored film designed to direct light away from the ground. But Meg Schwamb, a planetary scientist at Queen’s University in Belfast, who was not involved in the study, worries that the light is directed upwards and could make space telescopes worse off.

There are many unknowns at the moment, including the actual number of satellites.

SpaceX hopes to eventually expand the size of its fleet to 42,000 Starlink satellites. Many other companies are also in the market: Amazon, British satellite provider OneWeb, a Chinese company called Galaxy Space and even governments. In all, 431,713 satellites are planned to be launched over the next few years.

Translated by Luiz Roberto M. Gonçalves