Satellites are clogging up the night sky

The large number of satllites in orbit are causing problems for astronomers on Earth
31 January 2023

Interview with 

Matt Bothwell, University of Cambridge


this is a picture of a satellite orbiting Earth


The first artificial satellite was Sputnik 1, sent up by the Soviet Union in 1957. Since then, the number of satellites in orbit has exploded. In fact, it’s up by nearly 12% in the past 18 months alone, and the United Nations Office for Outer Space Affairs now estimates there are nearly 8300 satellites in orbit, although admittedly only half of them are actually ‘active’! To learn a  bit more about what’s whirling around the Earth above our heads, I went to see the University of Cambridge’s public astronomer, Matt Bothwell…

Matt - A satellite in the simplest terms is just something that orbits around something else. So they can be made by humans, like the Hubble Space Telescope is a satellite of the earth, but the moon is also a satellite of the earth. We call it a natural satellite. The earth is a satellite of the sun. Anything that orbits something else is a satellite of that thing.

Will - And when we talk about orbit. How does a body, a celestial body or a man made creation, how does that enter orbit?

Matt - Douglas Adams has this definition of flying where he says, it's the art of throwing it yourself at the ground and missing. And that's kind of what orbiting is. Orbiting is falling in a circle around the earth. So the Hubble Space Telescope is going in a circle around the earth or very close to a circle around the earth. And it's always falling down. It's being pulled down by earth's gravity, but it's also going sideways so fast that as it falls, the earth curves away at the same rate and it ends up just falling in a complete circle

Will - From all accounts. It does sound like we're perhaps hitting maybe a critical mass of the amount of satellites that we currently have in orbit around our planet.

Matt - Well, that's exactly right. There are of course thousands of artificial satellites orbiting around Earth right now. But we are entering this era where we are looking to have that number increased by orders of magnitudes. Listeners might have come across Elon Musk's Starlink project, the plan to put tens of thousands of satellites in orbit and blast down mobile internet around the world. But even Starlink isn't the only game in town. There are various governmental agencies and other private companies that are looking to do the same thing. We could very feasibly have a hundred thousand artificial bodies orbiting the earth within decades.

Will - And that presents problems in terms of space junk in orbit. But it also presents problems in terms of trying to look up into outer space.

Matt - It really does, yeah. Because these satellites are all reflective. Anyone that has seen the International Space Station go over will know that. You can see the ISS passing over and it looks like a pretty bright star as it flies around the Earth. The idea of there being a hundred thousand of these, it would be completely catastrophic for our views of the night sky. And I think that's bad for everyone. Honestly, it's bad for professional astronomers because as we are trying to take our images of the distant universe, if there are thousands of satellites getting in the way, it's going to be really hard to remove those contaminants in our image and get an unblemished view of the cosmos. It's also bad for amateur stargazers because they just want to get their nice pretty pictures of the night sky. But, I think it's also just bad for everyone. The night sky is this sort of universally human shared resource, where you can all look up and we can all see the night sky and all wonder about the universe. And I sometimes feel that putting satellites around the night sky, it's a bit like stringing power cables across Yosemite National Park or something. It's like the desecration of a beautiful natural resource.

Will - Satellites, man made satellites, are not huge and the night sky is very big. So is it really that much of an issue? All these satellites whizzing above our heads?

Matt - It really is because even though artificial satellites are not very big themselves, they do have these giant solar panels which are very reflective, which makes them very bright. And if there are just so many of them, they will get very crowded up there. You can even see it nowadays. There are astronomers right now going to professional telescopes and taking images of the night sky and the images that come back are just crisscrossed by trails and streaks and lines from these artificial satellites that completely ruin the image. And that's only in optical light, the light that we can see. It's potentially much worse than other wavelengths for radio astronomy, for example, these satellites, especially the mobile internet Starlink type satellites, are going to be blasting down wireless internet, which is gonna be great if you want wireless internet in the middle of the Pacific. But it could be potentially that there'll be no way to do radio astronomy from the surface of the earth. We could be completely blinded and deafened by the signals from these satellite fleets.

Will - So does that then create this potential catch 22 of, we have all these satellites in the way as we're trying to look up and we have to launch more satellites in order to get a clearer picture?

Matt - That could be the case. So for optical astronomy, there are ways of carefully removing the streaks, which are not perfect, but are better than nothing. But for something like radio astronomy, then yes, the answer might have to be going to space and that could be using yet more satellites, although it'd be an incremental increase, right? I mean if there's a hundred thousand satellites causing problems, putting one extra won't be a big deal. The other alternative is to go somewhere that's not the earth. There are these long-term plans to build a radio telescope on the fast side of the moon. The Chinese space agency landed a probe on the fast side of the moon a couple of years ago and measured the radio environment. The idea being that's the first step in the ultimate plan to build a radio telescope because that would be fantastic. That's the quietest place in the universe, radio-wise because there's thousands of miles of rock between you and the noisy earth.

Will - Presumably there's no easy fix for removing the amount of satellites or junk around the earth, otherwise people would've thought of it. But do you know of anything that's in play right now that might help make our atmosphere a little bit less crowded?

Matt - I don't think there's an easy fix unless you're a super villain, you're happy to start sort of blasting down satellites with high powered lasers. There's two different issues here, right? There's space junk versus the artificial satellites that are intended to be there and there are plans to get rid of space junk. So space junk, as listeners might know, are the sort of debris that orbit around the earth. It's everything from discarded rocket boosters to fragments from collisions of pieces of equipment. And there are, we think thousands of pieces of this space junk orbiting around the earth. And that is a problem. These bits of space zone do have to be removed, whether it's by a later or by a big net or something like that. But in terms of the artificial satellites, I don't think China will be very happy if we start blasting down their communication satellites. And in fact, the problem is only going to get worse. There are very few binding laws when it comes to launching stuff into space. It's a bit of a legal wild west, and that's why a private company like SpaceX can just launch thousands upon thousands of satellites. And there's, there's very few ways to stop that from happening.

Will - So the future of satellites is only set to increase then?

Matt - Yeah, I think the future of satellites is more satellites.


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