European Space Agency working on technology to ’embrace’ defunct satellites

By Nina Massey, PA Science Correspondent

The European Space Agency (ESA) is working towards tackling the issue of space debris with the technological version of a big hug.

The organisation hopes to be able to use tentacle-like mechanical arms to embrace a dead satellite and bring it out of orbit.

Other options considered have included a net being cast over the object, using a robotic arm, or using a harpoon.

At ESA’s ministerial council last month, the agency’s space safety programmes received a subscription of 412 million euro (£348 million).

Some of this funding will go towards a mission aimed at de-orbiting defunct satellites in Earth’s orbit.

The head of ESA’s Space Debris Office, Holger Krag, said work on developing the mission would start now, with the aim of designing something that could be used multiple times.

Speaking at EU Space Week in Helsinki, he said: “The goal is to make these removal actions happen more frequently, and therefore they need to be cheap.”

“The technology that we will most likely use now is actually consisting of some sort of arms, like tentacles, that embrace the object because you can capture the object before you touch it,” he said.

“The dynamics in space are very interesting because if you touch the object on one side it will be dragged away, so you can basically embrace it.

“So you can basically embrace it before you touch it and then you just embrace it closer as you dampen the tumbling motion.”

He added that it would be an extremely difficult exercise as it would mean trying to cooperate with an object whose state was unknown, and then get it down from space – something which has not been done before.

Space junk has become a growing concern as the debris in Earth’s orbit has the potential to collide, causing damage to other satellites.

Of the almost 4,500 satellites in orbit, only 1,500 are active.

The UK Space Agency has committed an investment of £374 million per year with the ESA to deliver international space programmes over the next five years.

This will secure its involvement in the mission to remove space junk.

Mr Krag said ESA had a fleet of 20 spacecraft to operate, and for these spacecraft they received several hundred collision alerts a day. But almost all of them were false alerts.

He added: “Why are they false alerts? Because there’s a limited accuracy of the data, and we are acting based on probability.

“So whenever the collision probability is higher than one in 10,000, we manoeuvre.

“But that means in 9,999 cases there would have not been a collision if you did not manoeuvre.”

He said that while there was an issue of manoeuvres using fuel, one of the biggest burdens was not being able to run a mission while they were carried out.

“If you run a very expensive science mission, in particular, and you have to interrupt the data for one hour in order to fit the manoeuvre in, you have a community of 1,000 scientists waiting for the data and that’s an economic loss that I wouldn’t even know how to put in numbers,” Mr Krag said.