A collision course with space junk

As more and more satellites and spacecraft are launched into space, small bits of space junk are becoming a problem, potentially risking future operations essential for monitoring Earth

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By Catherine Early

Deforestation, reforestation, oil spills, plastic pollution, glacial melt, illegal fishing and even the number of walruses on a particular ice sheet all have one thing in common – they can be monitored from space. 

Earth observation – the gathering of information about the planet’s physical, chemical and biological systems via remote-sensing technologies and imaging devices carried by satellites – has underpinned much scientific research in recent years. In fact, much of the data used by the Intergovernmental Panel on Climate Change in its reports was collected by satellites. Data on ice sheet melt, combined with powerful modelling, has led to predictions that the Arctic Ocean will be essentially ice free in summer at least once by 2050. According to the UK Space Agency, which is involved in multiple Earth-observation projects, half of the 56 types of data needed to accurately monitor and model climate change can only be measured from space.  

But what if the environment into which the satellites are being launched became too dangerous for this vital scientific research to continue? Space experts and operators are increasingly fearful about the danger posed by space debris – old satellites, spent rocket bodies, even maintenance tools that have remained in orbit after use, after they’ve run out of fuel, or simply after being dropped by astronauts. 

Debris can continue to orbit the Earth for hundreds of years. Already, around 36,500 pieces of debris around ten centimetres in diameter are in orbit, along with one million that are between one and ten centimetres, and 130 million pieces that are even smaller still. Although the majority of these fragments are tiny, they travel at about 10km/s, so even a tiny piece can cause catastrophic damage or even destroy another spacecraft. 

The danger was illustrated in 2014 when NASA’s Suomi NPP satellite, which collects data on long-term climate change and short-term weather conditions,
was almost hit by a piece of debris estimated to be between ten centimetres and one metre across. The debris was travelling directly toward the satellite at more than 27,000 kilometres per hour. At such speeds, it would not only have destroyed the satellite, but would also have created thousands of pieces of new debris that could, in turn, threaten other satellites. 

The NASA satellite was successfully manoeuvred out of harm’s way, but the need for such manoeuvres is becoming increasingly common. ‘We perform a collision-avoidance manoeuvre roughly every two weeks, which is frightening, but it’s normal today,’ says Holger Krag, head of the European Space Agency’s (ESA) space safety programme. ‘A very tiny, tiny piece could cause a lot of damage – you can basically assume that a one-centimetre object will kill a spacecraft.’

And they’re costly – hours are spent on the ground monitoring the skies, calculating the risk and planning manoeuvres, while the manoeuvre itself results in fuel wastage and missed data collection as instruments are turned off. As the number of collision alerts increases, the ESA believes that it will become impossible for operators to respond to them all manually and automated systems will be needed. 

A new space age

Fears about space debris have grown alongside the start of a new era in space flight. The number of satellites being launched has grown exponentially as smaller sizes mean several can be carried on a single rocket, cutting costs. This is coupled with a surge in demand for ultra-fast internet connections. These new satellites are typically being launched into low Earth orbit – roughly 160–1,000 kilometres above the Earth’s surface.

The vast majority of satellites currently being sent into space are small commercial satellites that weigh 100–1,000 kilograms. Private companies such as SpaceX, owned by entrepreneur Elon Musk, are launching satellites in large ‘constellations’ – huge clusters that work together to provide a more efficient and consistent service. 

The ESA estimates that there are 6,000 functioning satellites currently in orbit. That number has doubled in two years, according to Professor Andy Lawrence, regius professor of astronomy at the University of Edinburgh Institute for Astronomy and lead author of Losing the Sky, a book that documents the problem. 

Lawrence has analysed permit applications for upcoming satellite launches; if all of them go ahead, there could be as many as 100,000 satellites orbiting the Earth by 2030. SpaceX alone is planning to launch a 30,000-strong fleet of second-generation Starlink satellites. 

The fear is that unless radical action to prevent the proliferation of space debris is taken, the ever-growing cloud will reach a point where collisions will form an unstoppable cascade – the debris from one collision spawning others and so on and on and on – a phenomenon known as Kessler syndrome, after the NASA scientist who first predicted it. 

If this came to pass, low Earth orbit could become unusable for future space missions, including those by the Earth-observation sector. ‘The services we get from the EU’s Copernicus satellite mission, such as monitoring forest fires, measuring CO2 and sea-level rise, is at risk – some very important environmental data,’ Krag says. Higher orbits could be used for Earth observation, but that would be far more expensive, he adds. 

Debris tracking

Pieces of debris that are larger than ten centimetres can be tracked from Earth using ground-based sensors such as radar and telescopes, as well as space-based systems. The USA has the most advanced tracking capabilities under its Space Surveillance Network, but the EU and UK have recently been investing heavily in tracking technology. The ESA has a target for zero space debris from its own missions by 2030 and is hoping that others will follow. ‘We need to really watch out. We hope the ESA’s approach is followed, because otherwise, we will lose space before we even start using it properly,’ Krag says.

Concerns about space debris aren’t new. In 2007, the Inter-Agency Space Debris Coordination Committee, which is made up of governmental organisations, launched voluntary guidelines covering how to design, fly and dispose of space missions in sustainable ways that prevent the creation of new debris. According to the ESA, which reports annually on space debris, about half of spacecraft are disposed of in ways deemed to be sustainable – either using controlled re-entry into the Earth’s atmosphere, where they burn up, or by being placed in orbits that naturally decay within 25 years.

However, improving adherence to the guidelines on its own won’t be sufficient to prevent the now-exponential rise in debris, Krag says. Even when missions have been designed to follow best practice, the years-long duration of such missions can mean that a technical failure can result in loss of control of a spacecraft from Earth. If it’s still full of fuel, it’s even more dangerous than other debris as it can cause explosions, as well as hitting other spacecraft. 

Low earth orbit critical for science

Users of space are aware of the increased risks of debris and are concerned. Scientists at the British Antarctic Survey (BAS), for example, use Iridium satellite phones to communicate while working out on the ice sheets. The primary impact of losing this communication method would be on scientists’ safety, explains Mervyn Freeman, a senior space weather scientist at BAS. They maintain back-up via VHF radio for this reason, he adds. 

But BAS also uses satellites for remote sensing, including to measure the heights of the Antarctic ice sheets in order to calculate the speed of ice sheet flow and the rate and magnitude of ice loss. ‘That’s a really important part of our research that relies on satellite remote sensing, so losing low Earth orbit satellite capability would be very damaging,’ says Freeman.

Private satellite companies insist that their operations are sustainable. SpaceX says that all of its satellites are equipped with an onboard, autonomous collision-avoidance system that ensures that they can manoeuvre to avoid potential collisions with other objects, and that it deliberately uses altitudes below 600 kilometres so that any satellites it loses control of, or debris accidentally created, lose altitude and fall out of orbit to burn up in the atmosphere within five or six years. It claims that this greatly reduces the risk of persistent orbital debris and vastly exceeds international standards. Earth-observation company Planet, which operates a fleet of more than 200 Earth-imaging satellites that photograph every area on Earth daily, also says that it has purposely chosen to orbit its satellites at lower altitudes for the same reasons. 

However, SpaceX competitor Viasat is trying to halt the growth in satellite launches into low Earth orbit through the courts, arguing that they aren’t sustainable. Its own services mostly use geostationary orbit, which is higher than the low Earth orbit being used by SpaceX, making its services slower. It wants to force the US Federal Communications Commission – which grants permits for space launches – to apply the National Environmental Protection Act to space missions, which would mean that satellite operators would have to carry out environmental impact assessments in order to be granted a licence. 

A final decision by the US Court of Appeal hasn’t yet been reached, but Lawrence – who provided an expert statement on behalf of Viasat – hopes that it will set an international precedent for the impact of satellites to be properly thought through, and all risks assessed in advance. ‘The USA still dominates space activity, so a lot of people watch them and follow their lead,’ he says.

Many governments and private companies are now actively discussing solutions to the problem of space debris, both to improve the chances of avoiding collisions and to recover some of the debris. More 

advanced tracking is also being investigated as part of the solution. Apple co-founder Steve Wozniak has teamed up with a former Apple colleague, Alex Fielding, and Moriba Jah, associate professor of aerospace engineering and engineering mechanics at the University of Texas, to co-found a start-up, Privateer Space. The company plans to offer open-access and near-time visualisation of both satellites and debris in Earth’s orbit to help space users avoid collisions. 

At an international summit hosted in London at the end of June, UK science minister George Freeman announced the government’s new Plan for Space Sustainability, which includes a proposal to link the cost of insurance premiums and finance for space missions to compliance with industry standards on issues such as improving satellite repair and retrieval, and sustainable supply chains, so that more sustainable missions receive cheaper deals. 

Separately, the World Economic Forum, the ESA, MIT, the University of Texas and analytics and engineering firm BryceTech have launched the Space Sustainability Rating, which assesses missions on a variety of criteria concerning debris, such as collision-avoidance strategies, information sharing with other space users and the ease of detecting, identifying and tracking its spacecraft.  

Clearing space debris

But these efforts, even if successful, still won’t be sufficient to deal with the problem, according to some commentators. Ambitious plans are underway in several countries for active debris removal (ADR), which will see missions launched specifically to retrieve debris already in orbit. The first of these is due to be launched in 2025. Swiss start-up ClearSpace SA will lead a team that will capture a 112-kilogram defunct rocket part left behind by the ESA’s Vega mission in 2013. The vessel and the captured rocket part will then be brought down to re-enter the Earth’s atmosphere, where it will burn up. 

The US$86 million project is being paid for by the ESA, which is hoping to use it to demonstrate the technology before moving on to larger, more challenging objects, and even capturing more than one in the same mission, which would reduce the cost. The ESA’s target of zero debris by 2030 means that, if debris is inadvertently left behind, the agency will have to pay for a removal service to bring it down. It hopes that this work will inspire similar projects from other national space agencies and companies, and eventually, for an ADR market to be created, since it’s very difficult to completely avoid the creation of further debris.

The speeds at which objects move in space makes ADR extremely technically challenging. Another issue is the age of the debris being removed – more modern rockets and satellites can be designed with removal in mind, for example, by including docking infrastructure to which the removal vessel can connect. The piece of rocket targeted by the ClearSpace 1 mission doesn’t have such equipment. The vessel being sent to capture it has four ‘arms’ that will embrace the piece of rocket from all sides to bring it down. 

In January, the UK government announced £1.7 million for research and development on 13 projects that will track and remove debris from space. These include an AI-based tool being developed by start-ups Oxford Dynamics and In-Space Missions that can take autonomous action to avoid a collision. Meanwhile, start-up Magdrive and the University of Southampton are developing a ‘mothership’ to take multiple small spacecraft into orbit to be fired at debris and transport them to where they’ll burn up.

Jacob Geer, chief of staff at the UK Space Agency, says that new robotics being developed in the UK, along with a mission control centre in Oxfordshire, will control spacecraft that will dock with a piece of debris and remove it. These plans are expected to go live in 2026–27, he adds. 

Several other countries are investigating debris removal, including the USA, Japan and Australia. ‘Rather than getting the whole world to agree to the same measures, it can be really powerful for a few key countries to work together and share ideas,’ Geer says. 

Krag believes that at some point the international community is going to have to agree a legal regime so that the same principles and laws are used around the globe. ‘This is probably the biggest hurdle,’ he says. ‘We do have the willingness to invest in the technology, but the willingness to make an international rule? This I don’t see yet.’

Lawrence is pleased to see the efforts being taken forward, but is sceptical that any actions announced so far will happen quickly enough, considering the current pace of space commercialisation. ‘Like with other environmental issues, you see this kind of incrementalism – industry is trying to clean up its
own house to avoid governments imposing more draconian regulations,’ he says. ‘There is some good progress, but the trouble with this issue, like climate change, is that everything is changing so quickly and we haven’t got much time.