28th Jul 2021


Europe's space trash chief: situation getting worse

  • The European Space Agency is working on a space debris removal mission called e.Deorbit (Photo: ESA/David Ducros)

The trash situation in outer space caused by launches and defunct satellites is "getting worse" and risks making space off-limits for future generations, according to the European Space Agency's (ESA) chief space debris expert.

"We are adding more than the atmosphere can remove," Holger Krag, head of ESA's Space Debris Office, told EUobserver in an interview.

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"There have been several attempts to provide an international space law that has … requirements in there but this wasn't successful so far," he said, almost a decade after the European Union began an attempt to establish international rules on space debris.

ESA defines space debris as "all non-functional, human-made objects, including fragments and elements thereof, in Earth orbit or re-entering into Earth's atmosphere".

According to estimates, there are some 29,000 debris objects larger than 10 centimetres; 750,000 objects between 1cm and 10cm; and 166m objects smaller than 1cm.

When colliding, they could also break up even further, increasing the risk of new collisions.

Simulation of the crash between the Russian satellite Cosmos 2251 and US satellite Iridium 33

In 2009, this exactly happened when a defunct Russian satellite and a US commercial satellite crashed into each other - with enormous consequences for the operation of other satellites.

They left behind a large cloud of fragments, said Krag.

"Every second collision avoidance manoeuvre we are doing here at ESA is due to one of these fragments of the event. That basically means that after 2009 our efforts doubled."

According to ESA, there are some 4,700 satellites still in place, but only 1,800 of these are functioning.

They are operating at different altitudes, which determines how easily they can be pulled down by the Earth's atmospheric drag once their mission has ended.

Objects at 600 kilometres need about 25 years to be dragged down, while those at 800 kilometres need around two centuries, said Krag.

"It is around 800 and 1,000 kilometres altitude where the largest problem is," he said.

He spoke to EUobserver by phone from the ESA office in the German city Darmstadt, in the week of the launch of yet another satellite.

On 22 August, the ESA-operated Aeolus weather satellite was launched from Europe's spaceport in Kourou, French Guiana.

The satellite has a nominal lifetime of just three years.

Ahead of the launch, ESA's director of earth observation programmes Josef Aschbacher said that ESA was "very conscious" of the space debris problem.

He noted that Aeolus will fly at the relatively low altitude of 320 kilometres, which will allow ESA to de-orbit the satellite once its job is done.

"While de-orbiting most of the satellite will break up and will burn up in the atmosphere," said Aschbacher.

"There may be a small element coming down, we don't know exactly, but it will be a small debris that fall down. We will make sure that it comes at an area which is unpopulated, somewhere in the ocean," he added.

However, Aschbacher did not rule out that Aeolus would be up in space longer than planned.

"Typically our satellites live longer than the nominal lifetime. It could well be that the satellite lives longer, which of course we all hope," he said.

Horns of a dilemma

While this attitude makes sense from the point of view of the costs involved in launching and operating satellites - some €480m in the case of Aeolus - it also brings along risks, according to Aschenbacher's space debris colleague Krag.

He explained that there is a conflict between running the mission as long as possible to get value for money, and the reliability of the systems needed to steer the satellite out of harm's way.

"You don't throw away a functional mission when the payload is still working. But then you suddenly discover that other components that are important for the disposal have been ageing and then they don't function any more after ten years," said Krag.

Efforts currently mainly focus on prevention of new debris being added.

One measure is called passivation, which requires unused fuel to be burnt at the end of a mission; batteries to be discharged; and pressure released.

"We found that objects which are not passivated have a tendency to break up, sometimes even in an explosive manner. Then you leave many fragments behind," said Krag.

"But we need to do a second thing and that is disposal. Even a passivated object may not remain in space for too long because it might collide with something else," he noted.

The so-called Low-Earth orbit is the most congested region in space. (Photo: ESA)

Krag said that ESA is working on a mission that can demonstrate 'active debris removal' - removing a defunct object from space robotically.

"We want to demonstrate that in the next few years," he noted.

The European Union - of which the ESA is not a part - has also spent several million euros of research funding into debris removal.


A field related to the issue of space junk is that of space situational awareness (SSA) - knowing what exactly is out there.

ESA's collision avoidance work is based on data from the US, said Krag, noting that ESA had spent some €200m on SSA since 2008.

The European Commission recently proposed that in the 2021-2027 EU budget, an undefined proportion of a €0.5bn tranche should also be spent on SSA.

MEPs will be working on that legislative proposal in the coming weeks.

Centre-right Italian MEP Massimiliano Salini underlined the problem of space debris in a report earlier this month. He proposed a more ambitious budget of €0.6bn solely for SSA.

International treaty

EU member states, through the Council of the EU, have also began an international diplomatic effort to come to global rules.

This December will mark the 10-year anniversary of the council's agreement on a draft Code of Conduct for outer space activities, which included rules on space debris.

The draft has been amended several times since, but the EU has been unable to get all spacefaring nations on board - China and Russia have proposed a rival treaty.

The EU's draft code includes language on the peaceful purpose of space, which makes it unlikely that the US will come on board any time soon, after its announcement of plans to set up a Space Force.

"The initiative received support from a number of countries, but negotiations stalled in 2015," said a spokeswoman for the European Commission.

She said that since then, the EU has focused its efforts on the UN Committee on the Peaceful Uses of Outer Space's work on guidelines.

"We continue to believe that there would be value in agreeing a non-legally binding instrument which could possibly be negotiated in a UN framework," the commission spokeswoman told EUobserver.

Didier Faivre, director of the Guiana Space Centre, appeared not to be dogmatic about having an international space law.

"We need international cooperation. A law is good, but cooperation is by far better," he told EUobserver on the night of the Aeolus launch.

Standing next to him was ESA's director for space transportation, Daniel Neuenschwander, who echoed Faivre's sentiments.

"I'm convinced that a continent like Europe has to be an example, but not by big declarations or political announcements, but just by bringing the stuff back," he noted.

ESA's space debris expert Krag said he was "not fully optimistic" about the future.

He said that while there had been improvements on the prevention side, he was worried about plans for commercial launches of so-called mega-constellations of satellites.

Several companies have announced they would like to put such constellations in orbit, for example to help provide internet services across the globe.

"The number of satellites that are intended to be launched in these mega-constellation plans, if you put them all together, that is more than all of humanity has launched in the whole history of spaceflight," said Krag.

"It must be done in the right way and carefully, so that we do not spoil space for future generations," said Krag.

This article was updated on Monday 3 September 2018, to include comments from the European Commission

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