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Sci-Tech

Playing Pac-Man with space junk

The CleanSpace One project will deploy a satellite equipped with a net to go catch a small satellite and destroy it in Earth's atmosphere.

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Concept of CleanSpace One in action. EPFL/Jamani Caillet

Three years after the project was first announced, the École Polytechnique Fédérale de Lausanne has revealed details of a plan to send a satellite into space to scoop up space junk.

We humans sure do like to make a mess. As of 2013, according to NASA, there were over 500,000 pieces of space debris each larger than a marble orbiting the Earth, including more than 20,000 pieces each larger than a baseball, moving at speeds of up to 28,165 kilometers per hour (17,500 miles per hour).

Space debris occasionally falls out of orbit on its own, but the rate at which it increases is higher than the rate at which it decreases. Chunks of broken spacecraft, collision fragments and abandoned satellites pose hazards to operational satellites and space stations, degrading their performance and durability.

The EPFL's Space Engineering Centre embarked on CleanSpace One in 2012: a project to develop, build and deploy "janitor" satellites specially designed to clean up space debris. After three years designing the satellite, the team -- in collaboration with the EPFL's Signal Processing 5 Laboratory and partners at the University of Applied Sciences and Arts of Western Switzerland -- has revealed that it plans to launch the first mission in 2018.

In 2009, the EPFL had sent up the SwissCube -- a 10 centimeter by 10 centimeter type of miniaturized satellite for space research. It is this that the newly revealed cleanup satellite aims to retrieve as a proof of concept.

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CleanSpace One deploys a net to capture SwissCube in this artist's concept. EPFL/Jamani Caillet

There are several challenges. First, upon reaching orbit, it will need to be able to adjust its trajectory to match the orbital plane of the SwissCube satellite. Travelling at speeds of up to 28,000 kilometers per hour, the CleanSpace One will need to be able to grasp its target. Upon the project's announcement in 2012, concepts showed a grappling claw, but the redesigned satellite uses a sort of net in the shape of a cone that unfolds, then closes around its target.

"This system is more reliable and offers a larger margin for maneuvering than a claw or an articulated hand," explained Michel Lauria, professor of industrial technology at partner university Hepia, in a statement.

The SwissCube itself presents challenges, too.

"SwissCube is not only a 10cm by 10cm object that's tough to grasp, but it also has darker and lighter parts that reflect sunlight differently," said Christophe Paccolat, a PhD student working in the Signal Processing 5 Laboratory. "These variations can perturb the visual approach system and thus also the estimates of its speed and distance."

It only takes one small error in the calculations for CleanSpace One to miss, knocking the SwissCube out of orbit and into space.

If everything goes according to plan, though, CleanSpace One will jettison the SwissCube back toward the Earth's atmosphere, where it will burn up at re-entry temperatures of over 1,000 degrees Celsius (1,832 degrees Fahrenheit).