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Illustration of space junk orbiting Earth. Credit: ESA/P. Carill Illustration of space junk orbiting Earth. Credit: ESA/P. Carill

ESA plans to clear up space junk

Sen—The European Space Agency is planning missions to take out space junk. The agency's Clean Space initiative plans to tackle the problem directly, by designing dedicated removal missions. Initial plans will see ESA's 2015 Automated Transfer Vehicle (unmanned cargo freighter) include experimental optical sensors, that could be used for future rendezvous with 'unwanted targets'.

The problem of space debris is getting worse, with debris in low Earth Orbit believed to have increased by 50% in the past five years. According to ESA there are currently 22,000 objects larger then a coffee cup orbiting the Earth, but of those only 1100 are working satellites. 

More than one hundred European experts gathered at ESOC, the European Space Agency's operation centre in Germany, to discuss ways of actively removing debris from orbit. The meeting was part of the agency's new initiative to develop tools and techniques to reduce the environmental impact of the space industry and ensure its sustainability.

Reducing the amount of debris from future missions is not enough. According to ESA’s Director of Human Spaceflight, Thomas Reiter  “the only way to overcome this is to intervene and reduce the number of objects in the environment by an active retrieval of decommissioned objects.”

Even if all future missions were to stop, the amount of space debris would increase - this is because of something known as the ‘Kessler Effect’. Four decades ago, NASA space debris expert Don Kessler predicted that once past a certain critical debris mass, collisions form further debris and lead to more collisions, in a chain reaction, although collisions are still rare. The most severe collision to date happened in in low-Earth orbit between the US communications satellite Iridium-33 and the Russian satellite Cosmos-2251 in February 2009. The collision created around over a thousand pieces of space debris larger then 10cm in size.

Another risk to increasing space debris comes from old satellites exploding due to things such as leftover fuel or partially charged batteries kept illuminated in orbital sunlight.

The biggest threat of all this space debris is to crews on the International Space Station - where avoidance manoeuvres have become routine. And just last week the undocking of Europe's ATV (Automated Transfer Vehicle) was held up because it was on standby to give the station's orbit a boost to avoid two pieces of space debris. 

However the increasing amount of space debris is not just a threat to astronauts, it can cause problems to all of us here on Earth. Thomas Reiter adds "Modern life has become unthinkable without uninterrupted services delivered from space." A broken satellite could cause problems for everything from satellite navigation in our cars, to financial transactions, weather data and search and rescue. 

The task of removing space debris is not an easy one. According to Thomas Rieter "The removal of a large, uncontrolled object is an enormous technological challenge – but by removing on the order of five to 10 such objects per year, it would be possible to control debris growth while normal spacecraft activities could be continued."

Retrieval missions will need to be able to approach tumbling object in a safe manner, determining exact position and motion, and use various capture mechanisms. After that the vehicle would need to re-enter the Earth's atmosphere safely over unpopulated areas. 

However there is no silver bullet for tackling space debris, although Clean Space aim to finalise a prototype mission blueprint within three years. The news comes as Astrium UK reveals plans by engineers developing technology to harpoon rouge satellites.

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