What happens when today’s treasure – satellites that give us access to broadband internet and accurate weather forecasts among other things – become tomorrow’s trash? Or, in other words, where does all that space junk go? And what does climate change have to do with it? Last month, a team of aerospace engineers at MIT released their findings from a research study on the effects of climate change on satellites in the Earth’s upper atmosphere. Will Parker, PhD candidate in Aeronautics and Astronautics at MIT, and lead author of the study, joins The Excerpt to discuss how global warming affects satellites.Let us know what you think of this episode by sending an email to [email protected] Transcript available hereAlso available at art19.com/shows/5-ThingsSee Privacy Policy at https://art19.com/privacy and California Privacy Notice at https://art19.com/privacy#do-not-sell-my-info.
Chapter 1: What is the impact of climate change on satellites?
Hello, and welcome to The Excerpt. I'm Dana Taylor. Today is Thursday, April 3rd, 2025, and this is a special episode of The Excerpt. Last month, a team of aerospace engineers at MIT released their findings from a research study on the effects of climate change on satellites in the Earth's upper atmosphere. What happens when today's treasure, satellites that give us access to broadband internet,
and accurate weather forecasts, among other things, become tomorrow's trash? Or in other words, where does all that space junk go? And what does climate change have to do with it? Here to discuss the impact of global warming on satellites is Will Parker, PhD candidate in aeronautics and astronautics at MIT, lead author of the study. Thanks for joining me, Will.
Hey, thanks, Dana.
Chapter 2: Is space already too crowded with satellites?
First, is it time to change our thinking regarding the vastness of space and looking at the total number of satellites? I understand there are more than 11,900 circling the Earth right now. Is it already too crowded up there?
Yeah, you know, we used to live in this world where we had a mentality that space is big and we didn't have to be sustainable in the way that we acted in space because we didn't have to worry about collisions between satellites or debris objects. It was mostly a clean environment when we started our operations in space in the late 50s. Today, the environment is very different.
We have, like you said, tens of thousands of objects that are orbiting Earth, many more smaller debris objects that we have a hard time tracking. And so because of that, satellite operators constantly have to dodge debris. So the operating environment is becoming really complex and really difficult.
And that's bad news for the long-term sustainability of the environment for us to use for all the things that we rely on spaceport.
According to the Associated Press, there are more than 7,300 satellites in low orbit, which is where we count on our space junk disintegrating, right? Can you explain this to me as though I were one of your children, just how this part of the atmosphere works?
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Chapter 3: How does the upper atmosphere help clean up space junk?
Sure. Well, we rely on the upper atmosphere to clean up low Earth orbit. So, you know, we like to think of space as being a vacuum, but really there's a little bit of air at the very top reaches of the atmosphere where most of our satellites are operating. Basically, if it weren't for that atmosphere, any debris, any satellite that we abandoned in space would stay there forever.
We rely on that atmosphere to basically reduce the energy from our satellites so that they spiral towards the Earth and eventually deorbit. So we need that cleaning force. If we don't have that force, then we would have these things in space forever. That is catastrophic to the environment, right? We have no way to remove the old junk so that we can have stuff to do in the future.
What did your study reveal regarding the impact of climate change on the ability of the Earth's atmosphere to keep debris from piling up in space?
So we built on some previous studies that have started to show that while we see a significant warming effect from greenhouse gases in the lower atmosphere, we actually see pretty significant cooling and contraction in the upper atmosphere. And so that's caused by two things.
One of them is that the greenhouse gases in the lower atmosphere trap heat close to the surface of the Earth and prevent it from reaching the upper atmosphere. And the heat that does make its way into the upper atmosphere is emitted more easily into space. So those two mechanisms together mean that we're seeing a cooling effect in the upper atmosphere where most of our satellites are operating.
And because of that cooling effect, we're seeing that the entire atmosphere is contracting. So it's retreating away from low Earth orbit where we rely on that atmosphere for drag on our satellites. The effect of that retreat, that shrinking of the atmosphere, is that it's not doing as good a job at cleaning out low Earth orbit.
And again, we rely on that cleaning force because we have no other way to remove most of this debris. So the danger and the thing that we found is that it actually reduces the number of satellites that we can sustainably operate in low Earth orbit because we don't have this cleaning force.
So if there's a collision or an explosion, anything that's going to cause debris in low Earth orbit, the consequence of that event is getting much greater over time because it'll take a lot longer to clean it up.
Do you have increased concerns about the Kessler syndrome where collisions of space junk create a cascade of increasing debris? What's currently being done to prevent satellites from colliding?
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Chapter 4: What did the study reveal about the upper atmosphere's cooling effect?
So the Kessler syndrome is always a concern, right? This runaway growth in the debris population. It's something that we take a lot of care to prevent. It's important that we're able to model these scenarios and understand how our actions in terms of how we populate space and how satellite operators are acting impact this long-term sustainability.
Because once this cascading debris generation starts, there's no way to stop it. And once space is cluttered, it can stay cluttered for decades or longer. because it'll close off key routes to space. Today, satellite operators are avoiding collisions by performing maneuvers.
So back in the 80s, 90s, early 2000s, we sort of came up with these strategies for how we would avoid collisions between satellites. But back then, we, again, just figured that space was big. So it was mostly just an academic exercise. Today, that is not the case. It is fully operational. The Starlink Constellation did over 100,000 collision avoidance maneuvers last year.
So it's something that is very much used in practice by necessity, right? We need to avoid debris objects and other satellites because it is getting so congested in space. And that's making it more difficult to operate spacecraft there.
Well, by your estimation, how much time remains to offset greenhouse gas emissions before we see a significant decrease in the number of satellites that can be maintained in low orbit?
Well, our study went to 2100 and we saw that relative to the year 2000, we're seeing in the worst case scenario, at least a reduction of 50% in our carrying capacity, the number of satellites that we can sustain. It depends, right? The point of the study is to be able to show that we have a lot of levers at our control to be able to manage the space debris problem.
is to more effectively manage our access to space and make sure that internationally we have rules of how we operate spacecraft and how we manage our use of space. The other that is maybe unintuitive is that you don't need to be an aerospace engineer to make a difference in reducing the space debris problem.
Everybody can sort of do their part to try to reduce the greenhouse gas emissions and every country should We're trying to do that for lots of reasons, right? We don't need more reasons to reduce our greenhouse gas emissions, but it turns out that reducing those emissions not only helps us on Earth, it also helps to enable the long-term sustainability of space, which was a cool outcome.
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Chapter 5: What is Kessler syndrome and how can it be prevented?
And the adverse effects will not be distributed evenly across the globe, correct?
Yeah, so what we found is in the lower part of the atmosphere, we can fit a lot of satellites if we're trying to avoid this long-term debris accumulation that we're looking at. Because as long as you stay in the part of the atmosphere that is very thick, then any time you have some sort of debris generating event, it'll be removed from orbit very quickly.
And so what we recommended in the paper is if you want to make sure that you are not doing long-term damage to the environment, it's really important that satellite operators reduce the altitudes that they operate at. So if you fly at a lower altitude, it ends up being a little bit safer for the overall environment.
And it's something that I think we're going to start to have to do more and more as time goes on.
Is the Earth's atmosphere the only way to get rid of space junk? Are there any other options here?
So for really large pieces of space junk, so I'm talking large satellites that are abandoned or we have upper stage rocket bodies that are floating around in space. For those things, there have been several companies and governments that have been working on what they call active debris removal strategies.
So that means that we take basically independent satellites, we launch them to space specifically to remove these large objects. Basically, it's a one-to-one. We send up a satellite to remove a satellite. That's incredibly expensive. It's something that we need to do, but it is not a scalable problem. We have hundreds of millions of objects when you get down to the really small scales.
We have no way to remove those objects. We can remove maybe five or 10 objects a year using this active debris removal, but that will never, ever scale to the problem. I liken it to direct air capture for removing greenhouse gases from the atmosphere. The direct air capture is useful for sort of trying to clean up the mess that we've already made.
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Chapter 6: How much time do we have to reduce greenhouse gas emissions?
But it's always a lot cheaper to not make a mess in the first place than it is to clean up a mess that has already been made. So that's what we're advocating for. I think that the active debris removal will be a useful component to trying to ensure this long-term sustainability. But really, the atmosphere is all we rely on to do 99.9% of the cleanup.
Besides a loss in critical services such as GPS and global communication, does space junk pose a hazardous risk to those of us down here on Earth?
Well, we've seen recently, certainly in the news, lots of instances of space debris that makes its way all the way to the ground and maybe poses a hazard to people on the surface. That is certainly a concern, and it's something that I think will constrain our space activity. It's important to, one, be able to understand what will these satellites do as they're burning up in the atmosphere.
Will they burn up completely? In a lot of cases, we thought they would, and they're not in practice. So that's a concern, and that's something that the space industry needs to work on. The other component is we need to sort of better coordinate between all of the decision makers and all the people that need to know the information that we have available.
Chapter 7: What role can individuals play in reducing space debris?
So if we have a satellite that's reentering that may not make it to the ground, we need to do a better job of coordinating with airline pilots, with people in the ground that may be impacted in advance. And that's certainly a concern, I think, for people's safety.
Obviously, it's a pretty low risk just because we don't have satellites reentering all the time and the Earth is very big and it's mostly water. So we haven't seen an issue yet. But as we're launching more things into space and as the atmosphere is removing more of those objects, we're going to start to see more of these reentries happen. So it's important to get a grip on that problem.
What are satellite mega constellations and is the rate at which satellites have been launched over the last few years sustainable?
The mega constellations are a new trend in the way that we operate satellites. It was initially driven by companies like OneWeb and SpaceX. Today, SpaceX's Starlink constellation is over 60% of all of the active satellites in orbit. And they operate, at this point, many thousands of satellites in a very tight altitude regime.
And they are designed in a very structured way, so they can fit a lot of satellites in a very tight space. The idea with these mega constellations, in particular, these large constellations in low Earth orbit, is mostly to provide broadband internet to people on Earth. And the reason that they are in low Earth orbit, very close to the surface, is because we have pretty low latency.
So for internet, I can communicate with a satellite very quickly, whereas historically, our satellites for internet had to be really far away. And so it took a long time for that signal to propagate. These constellations are an entirely new means of operating in space. And so the rules are fundamentally changing.
We don't have a lot of regulations in the way that we use space, especially in the way that we use frequency spectrum to be able to communicate with our satellites. So there are a lot of constraints on operations that these constellations are now starting to stress because we've never had to think about populations in space this large.
And that's causing some significant disagreement, I think, within the industry.
Well, as you know, only a small number of countries have space launch capabilities. What are some of the ethical and geopolitical considerations of space junk here?
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