Satellite constellations, networks of multiple satellites that can number from a few dozen to tens of thousands, are interfering with scientific research using ground-based telescopes, but now a new study looks at how they might affect space-bound telescopes like Hubble.
The Hubble Space Telescope has produced some incredibly beautiful photographs of galaxies and nebulas that we have come to marvel at, but it’s also made incredible scientific discoveries, including measuring the rate of our universe’s expansion.
But that science could be threatened if all the proposed satellite megaconstellations — groups of thousands of satellites launched by companies like SpaceX and Amazon — come to fruition.
The authors of the paper published today in Nature looked specifically at Hubble, NASA’s SPHEREx — a near-infrared telescope that was launched last March — the European Space Agency’s proposed ARRAKIHS (Analysis of Resolved Remnants of Accreted galaxies as a Key Instrument for Halo Surveys) and China’s planned Xuntian telescope.
The authors calculated that should the 560,000 proposed satellites be launched into orbit in the coming decade, roughly 39.6 per cent of Hubble images would be affected, and 96 per cent of the other three would be affected.
As satellites move across the sky, they create long streaks of light across any images telescopes take. They can also interfere with radio astronomy, as they “leak” electromagnetic radiation in low frequencies.
The authors calculated that the average number of satellites seen per exposure (which can be minutes long) would be 2.14 for Hubble, 5.64 for SPHEREx, 69 for ARRAKIHS, and 92 for Xuntian.
“I remember when … sometimes we saw like one satellite [a night], and it was very strange to see. Now this is getting more and more common, way too common,” said lead author Alex Borlaff, a NASA research scientist at the agency’s Ames Research Center.
“In the last two, three years, we started seeing more satellites, even in some space telescopes, like Hubble. They pass in front of them because they share the same orbits.”
Curious to see how these megaconstellations could impact astronomical research using space-based telescopes, Borlaff and his co-authors decided to do an estimation, resulting in their latest findings.
A growing problem
In 2019, there were roughly 2,000 satellites in orbit. Today, there are roughly 15,000, largely a result of SpaceX’s Starlink satellites. But the company is not alone: Amazon has just started with its Kuiper constellation (with plans for 3,200 satellites), OneWeb has 632 planned, and China is planning to launch 14,000. That’s just some of those proposed.
The reason for the boom in satellites has been due largely to the lower cost compared to a decade earlier, with reusable launch vehicles and smaller payloads, like CubeSats, which are roughly the size of a bread box.
And these satellites, like the ones from Starlink, are mainly providing and improving internet accessibility, particularly in remote locations across the globe. So they’re unlikely to be going anywhere soon.
At the moment, ground-based observatories can pause their scientific research when they know a satellite may be passing in front of their telescopes, but it’s a nuisance and takes more work, Borlaff said. And while space-based telescopes may be able to do the same, it’s not the case all the time.
Structure of proposed satellite telecommunication constellations in Low Earth Orbit from 1958 to 2037 (predicted). The altitude of satellites is compared to the orbits of Hubble Space Telescope, Xuntian Space Telescope (CSST), SPHEREx, and proposed ARRAKIHS mission.
But Borlaff said if it’s happening 96 per cent of the time, as their simulations suggest, “then we may have a problem.”
As well, it’s important to note that not all satellites will be affected. For example, the James Webb Space Telescope is in an orbit that takes it far beyond low Earth orbit. The Nancy Grace Roman Space Telescope, which is slated to launch in 2027, will also similarly be unaffected.
Other consequences
Some people may be wondering why it’s a big deal: just retake the images or get rid of the streaks. But there’s more to it than that.
“One of the problems is that some astronomical targets are, for example, things that you don’t know where they are. Like, for example, looking for a new asteroid,” Borlaff said. “And asteroids are very interesting because they look like satellites. It’s just a thin line of light just crossing in your image.”
So if you have many lines across your images, it may be blocking out a potentially hazardous asteroid, he explained.
Astrophysicist Aaron Tohuvavohu says perhaps we need to rethink where we put those space telescopes.
“We’re just going to have to build space telescopes farther away,” said Tohuvavohu. “I mean, astronomers have always gone above all the disturbances. That’s why we put things on mountains. And we thought space was above all the disturbances, and it turns out that depends where in space.”
But that may not be an option, according to Borlaff, particularly for telescopes that already cost millions to billions of dollars. To launch a telescope beyond low Earth orbit would raise that cost, he said. As well, some of the telescopes are meant to be in low Earth orbit.
Tohuvavohu says that for some instruments, raising their orbits will have repercussions for astronomers.
“I think that what it will do for astronomers, in particular, is put a larger cost and onus again on how and where we build our instruments and how we operate 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, assume we can solve the infrastructural challenges. We can’t move your eyeballs and your backyard to space, right? So I’m actually much more concerned about the effects that it has on our shared cultural ownership of the night sky,” Tohuvavohu said.
“What that means for what we see when we look up. I find myself thinking about that much more often than I do about the impact on my research.”
Borlaff says he is also concerned about how these satellites could have other impacts, such as causing confusion among birds who use the stars to navigate. Then there’s also the concern over these satellites’ end of life, where they burn up in our atmosphere, leaving behind soot and vaporized metals.
Then there are the effects on humans.
“There are cultural problems as well. The sky and the position of stars have been used for generations in humanity to figure out stories and and and pass on the memories from our elders,” Borlaff said.
“Space is for everyone, and it will affect everybody.“
