Satellite constellations, networks of multiple satellites that can number anywhere from a few dozen to tens of thousands, have hampered scientific research using ground-based telescopes, but now a new study is looking at how they could affect space telescopes such as Hubble.
The Hubble Space Telescope has taken some incredibly beautiful photographs of the galaxies and nebulae that we admire, but it has also made incredible scientific discoveries, including measuring the rate of expansion of our Universe.
But that science could be at risk if all the proposed satellite megaconstellations—constellations of thousands satellites launched by companies such as SpaceX and Amazon – come true.
Authors of the article published today in the journal Nature specifically looked at Hubble, NASA SPHEREx – a near-infrared telescope launched last March – proposed by the European Space Agency ARRAKIKH (Analysis of resolved accreted galaxy remnants as a key tool for halo research) and China's plan Xuntian telescope.
The authors estimate that if the 560,000 proposed satellites were launched into orbit in the next decade, it would affect about 39.6 percent of Hubble's images and 96 percent of the other three.
As satellites move across the sky, they create long streaks of light in any images telescopes take. They can also interfere with radio astronomy by leaking low-frequency electromagnetic radiation.
The authors calculated that the average number of satellites visible per exposure (which can last several minutes) for Hubble would be 2.14. 5.64 for SPHEREx, 69 for ARRAKIHS and 92 for Xuntian.
“I remember when… sometimes we saw as if one satellite [a night]and it was very strange to see. It's becoming more and more common now, almost too common,” said lead author Alex Borlaff, a NASA scientist at the agency's Ames Research Center.
“Over the last two to three years, we've started to see more satellites, even in some space telescopes like Hubble. They pass in front of them because they have the same orbits.”
Curious about how these megaconstellations might affect astronomical research using space telescopes, Borlaff and his co-authors decided to conduct the assessment that produced their latest results.
A growing problem
In 2019, there were approximately 2,000 satellites in orbit. Today there are about 15,000, thanks largely to SpaceX's Starlink satellites. But the company is not alone: Amazon just launched the Kuiper constellation (with plans for 3,200 satellites), OneWeb plans to launch 632 satellites, and China plans to launch 14,000. These are just a few of the proposals.
The reason for the satellite boom has much to do with lower costs compared to a decade ago, with reusable launch vehicles and smaller payloads such as CubeSats, which are roughly the size of a bread box.
And these satellites, like Starlink satellites, basically provide and improve Internet access, especially in remote locations around the world. So it’s unlikely they’ll be going anywhere anytime soon.
Currently, ground-based observatories can pause their research when they learn that a satellite may be passing in front of their telescopes, but this is an inconvenience and requires additional work, Borlaff said. And while space telescopes can do the same, that's not always the case.
Structure of proposed satellite communications constellations in low Earth orbit from 1958 to 2037 (projected). The altitudes of the satellites are compared with the orbits of the Hubble Space Telescope, the Xuntian Space Telescope (CSST), SPHEREx, and the proposed ARRAKIHS mission.
But Borlaff said if that happens 96 percent of the time, as their simulations suggest, “then we might have a problem.”
It's also important to note that not all satellites will be affected. For example, the James Webb Space Telescope is in an orbit that takes it well beyond low-Earth orbit. Rome's Nancy Grace Space Telescope, scheduled to launch in 2027, will also be unaffected.
Other consequences
Some people may wonder why it's so important to just retake the pictures or get rid of the streaks. But that's not all.
“One of the problems is that some astronomical targets are things that you don't know where they are, for example. For example, searching for a new asteroid,” Borlaff said. “And asteroids are very interesting because they look like satellites. It's just a thin line of light intersecting in your image.”
So if your images have a lot of lines, they may be blocking a potentially dangerous asteroid, he explained.
Astrophysicist Aaron Tohuvavohu says we may need to rethink where we place these space telescopes.
“We’ll just have to keep building space telescopes,” he said. Huge flow. “I mean, astronomers have always been above all the disturbances. That's why we put things in mountains. And we thought that space was above all disturbances, but it turns out that it depends on where exactly in space.”
But that's not an option, Borlaff said, especially for telescopes that already cost millions to billions of dollars. Launching the telescope beyond low-Earth orbit would increase that cost, he said. In addition, some telescopes must be in low Earth orbit.
For some instruments, raising orbits will have implications for astronomers, Tohuvavohu says.
“I think for astronomers in particular this will lead to increased costs and responsibility for how and where we build our instruments and how we use them,” he said.
Beyond their research, both astronomers are concerned about how this also affects our enjoyment of the night sky.
“All other things being equal, let’s assume that we can solve infrastructure problems. We can't move your eyes and your backyard into space, can we? So I'm actually much more concerned about the impact this is having on our shared cultural ownership of the night sky,” Tohuvavohu said.
“What does this mean for what we see when we look up. I think about that much more often than the impact on my research.”
Borlaff says he's also concerned that these satellites could have other consequences, such as causing confusion among birds that use the stars to navigate. Additionally, there is concern about the end of life of these satellites as they burn up in our atmosphere, leaving behind soot and vaporized metals.
Next come the consequences for humans.
“There are also cultural problems. The sky and the positions of the stars have been used for generations. in humanity to unravel the stories and convey the memories of our elders,” Borlaff said.
“Space is for everyone and it will affect everyone.“
