Rubbish falling from the sky

They’re invisible but they exist, and they’re falling back to Earth: these are the waste products we continue to generate through space activities, and they’re cluttering the orbits above our heads. On average, an uncontrolled object falls from the sky once a week. In response, the European Space Agency (ESA) has launched a strategy to address the issue by 2030. Here’s how.

There is no more room in space around Earth’s orbit—this is the stark conclusion of the latest Space Environment Report from the European Space Agency, published in July 2024. Space debris continues to increase, and in 2023, more satellites were launched than ever before. These satellites now must navigate an ever more complicated path to avoid colliding with each other and with the debris. The Agency has made it equally clear that if we continue on this path, all extra-orbital activities, both public and private, will no longer be sustainable.

This is why ESA’s Zero Debris strategy includes, among other things, a goal that by 2030, fewer than one object in a thousand should generate space debris, and fewer than one object in 10,000 should cause incidents by falling back to Earth. How did we reach this point? We asked Tiago Soares, chief engineer of the Clean Space initiative and technical coordinator of the strategy.

From the data published by ESA, there are about 13,000 satellites in space and 10,000 are still functioning… the other 3,000 are for what? Why are they still there? What happens when a satellite breaks down?

Actually, the picture is much better now because there were a lot of launches in the last years, so it looks like it there a small percentage of non-functioning satellites: at some point, they were the majority of the objects in orbit. Those were satellites launched in the past, when countries and companies were not conscious about the fact that space may be infinite, but our orbits are not and they are resource in the end. Those satellites were launched without any means to deorbit:  they were thought they operate until they can and then they stay in orbit, even for thousands of years. So it’s not something that will be solved anytime soon. And we’ll have eventually more of those, and that’s what we’re trying to prevent right now: times have evolved, hopefully people are thinking a bit more long term, but leaving all these different satellites in orbit was not considered something that would hinder us in the future. It was only between the 1970s and 1980s that the Kessler syndrome, or the exponential growth of space debris, was conceived: every time we have a collision or an explosion, it will have thousands of small debris that will be released and imply risk on the other missions. And if one of the small debris hits another satellite generates more debris, in a cascade effect. It still took until the year 2000s to have some actual standards on how to design satellites in protecting the orbits but those are by now obsolete.

Again from this data, there are about 36,500 space objects catalogued and surveyed and 40,000 debris objects larger than 10 cm, which becomes over a million from 1 to 10 cm…. How are they surveyed and in what part of orbit are they located?

The objects are in the most interesting orbits for human beings, so that’s where we lost the most satellites, and that’s where the accidents eventually happened. Most of them are in the orbital region that we call low Earth orbit, Leo, that was used a lot for in the past for Earth observation, and now more and more for telecommunication satellites as well. The other area is Geo, the just stationary satellites, that were used in the past a lot for telecommunication, television and today they are still used for telecommunications quite a bit. Also sometimes worth observation. Those two areas are the most polluted one or where we are starting to have more design rules to avoid generating debris. In particular, there is some orbits in the lower Torbet region, around 708 and 1200 hundred kilometres altitudes, that are really quite crowded with debris because they were very much used in the past and still used today. That’s also where you can launch more objects and more easily: those are the most interesting orbits to be able to see the Earth in good conditions, also from a scientific point of view.

How are these debris surveyed?

Radar system is on grounds more and more, that starts to be optical systems to to track them. These systems are able to catch or to observe objects above around 8 to 10 centimetres. We can detect smaller ones, for example, with longer exposure radar measurements, but you cannot track them. Not know if there gonna be a risk for your satellite in two days. So, actually, debris bigger than one centimetre is what we call a little one because it will already make your satellite mostly. We have a big gap in between those very small ones, below 1 millimetre, and the ten centimetres, where we don’t see and those are very dangerous ones. Maybe the most dangerous because we have, we expect to have more than 1,000,000 Debris above 1 centimetre around, then we cannot see them.

I think about the fragment that pierced the roof of an house in Naples, Florida. How do we protect us from this kind of collisions?

That’s another thing that in the past was not really taken care of. That is what we call on “ground casualty risk”. The satellites were designed to perform, so they are made up of materials very resistant to high temperatures, high pressure and that makes them very difficult to demise when they reenter, we call it “demise to melt”. During the reenter there are objects like tanks (this case was a battery pack) that did not were not designed to demise, in a way that’s they will not pose a risk on Earth. Now we are starting to have rules on that, but it’s still a technology that we are trying to develop. We took quite a lot of research and development in the last years, Europe is quite advanced on that with respect to the rest of the world, but we don’t have a lot of products in the markets that are really designed for demos: this is one for me. I’ve been pushing a lot for this type of technology, because we had tanks falling in India, Brazil in the last years. In Florida it fell in a house like we did not hurt anyone. And there is a court case going on because of this. So it all it can also push a bit the need for developing demisible solutions, especially with the growth of the number of objects in our orbits. It’s really important that we take care of the demise of the satellites when they come down so that they don’t injure anybody.

ESA reported that more satellites have been launched in the last two years than in six decades of space exploration: what are the causes?

There was clearly a boom of the commercial missions. In the last years, of course, SpaceX has been completely disruptive. I think we had launched about 6,000 satellites before that and the launch for one constellation of the starlinks in a few years drived a lot the trend, but there are many of those constellations being developed: space is trying to be is privatised by now, commercially driven. In the next years we’ll see even higher numbers: it’s not something that will revert. At the moment, it’s very much linked and driven by the telecom markets, Internet from space. We also see the weight this has in strategic situations like in Ukraine, so we can expect that more States will want to have their satellites. I expect to see more consolidations of Earth observation, environmental monitoring, disaster monitoring. I believe that game have changed.

And that’s why I said for me it’s very clear that the rules we had before 2008, so the first international standards about space debris mitigation, are completely not updated and they do not cope with the current needs.

And that’s why we started the Zero Debris Strategy, that now is a community driven initiative, there are 180 entities by now that have confirmed they want to sign. We are trying to say we need to go in a different direction. We need to produce and get consensus around standards, but it takes a long time. So we tried to agree or to design a few concrete targets that your community can strive for and develop technology for even before the standards are there and the law is there so that we can push the State to school. Independently, just of waiting for requirements to be available.

Following the circular economy approach applied to space, how can the production of space waste be reduced and/or mitigated from prototyping to end-of-life?

That’s to be done in the market.  We are trying to enable that, so we need to start thinking circular, the removal of garbage from space first, second reuse and eventually, in the future, recycling. But this is something that needs to be accelerated a lot for sure. In Europe and also Japan there are few missions in the pipeline about activity removal. There are some private investor investments, insurances are starting to pay attention to this issue, so the removal of risk from orbit is something that is starting. We may need when technology is moving, maybe also regulations will start moving.

In the Zero debris approach we say: “we don’t leave garbage behind”: something can go wrong and even though it was designed to be perfect, your satellite is still there because it has failed. So you need to be able to remove that risk from orbits: and that’s something we want to really strive for.

And after we mastered that, we start talking really about: can we reuse it? can we actually do something about with the garbage captured in the space? This could be very interesting, because it can open up an new world of possibilities: instead of launching the full satellite, you could launch parts to repair. There are satellites that have been operating for more than 20 years and they’re fine, then others that fell after one year because one element failed but it doesn’t mean that all the equipment failed, right? In-orbit reparations with the robotic means you are able to repurpose parts of the satellites that’s have a longer lifetime and/or restore only the necessary part to the failed satellite. But this thinking completely changes the design process of the aerospace industry. And we may need some captains that bring this along and start doing things in this way and that’s what we are trying to promote. We launched an initiative called Circular Economy, a call for ideas and we’re trying to starting five studies on systems to do that in in the coming months. We also started another initiative called Ecostar to say: how can we make our satellites green? For sure, modularity could be a part of this solution. In the Clean Space Office, we are starting a lot of initiatives to prepare the future in that way. Space is starting to be more and more commercial, so we can try to accelerate those processes. But of course, we need companies to also engage into this and see this as an opportunity.

Are there any technologies that have already been developed and/or are being developed to clean up space?

It’s a very complicated mission. We have been working on it for a while. We should have the first removal mission in Europe in 2028 and we have developed some big tentacles that close around the satellite and try to bring it down again. Now the future satellites of ESA are embarking interfaces specifically to be captured. So if they fail, it will be in theory simpler to capture them and bring them down because they have clear markers to help us navigate. If you think about it, a piece of debris will be dancing in space. It will be not controlled.

So now we have to come with the other satellites and start synchronised motion in space, in a sort of space dance. In this dance, we should approach it from a certain angle and capturing it a certain point.

For many people, it’s science fiction. I think it’s not anymore, and we’ll have mastered this in the coming years, when we’ll have the first time demonstrated that we can do this in space. For me there are some key functions: the first one is to be able to reconstruct the attitude from ground, so we’ll have some laser markers that allow us to know how the satellite is moving when we come with our chaser using cameras. Then it will be important to have a physical interface to be grabbed, because that is also not there. And another thing is to slow down these tumbling motions, so we need something that dissipates the energy of this tumbling motion and slows it down so that it’s easier to do this dance.

What have been the most important achievements in the years of Zero Debris Strategy and the biggest challenges that you are facing?

Technically, the biggest achievements was starting to have these interfaces on board of the satellites of the future. This includes for us an improvement and a regular monitoring of the health of the satellites to prevent unknown failures in orbit that we cannot take care anymore. After 2008, we said: when you design something, you should guarantee a certain reliability. But over the lifetime, it was basically up to the operator to decide how to keep on going or not. And now we’re trying to put some checks that would help taking a decision. These are for me two important technical advances. The removal missions will be a major announcement. Then, I think putting such a community together behind five targets in a 2-pages document was really one of the highlights of my career, honestly. Because I think it’s it feels a bit like the 1 and 1/2 degrees from the Paris Agreement: now we know how to measure our success.

Are we getting closer? Maybe we’ll not reach it, but we have something to aim at. This is very important and was not there for space sustainability. On the challenges, everybody’s scared of changing things in space and it’s very hard to make change in space. We talk about space as a very innovative field but it’s not easy and things are changing. Daring companies are going much faster but the culture needs to change and I think a new mindset may cost some money in the beginning, but in the end, this is the future.

You cannot do space without Zero debris, without clean space, so you know it can cost a bit of money. I think it will pay off. And the faster we move, the better.

This is something not there yet in the culture of the space sector and you know, I think it’s something that as a society we struggle with for climate change and we struggle with it, any sustainability issue and it’s still a fight every day. It’s a fight.

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