Space researchers in Switzerland are seeking funding to build a spacecraft that will home in on a redundant satellite, grab it, and drag it down to burn up when reentering the atmosphere. The idea is to stem the tide of debris that is littering space around the Earth.
Researchers at the Swiss Space Center at the École Polytechnique Fédérale de Lausanne have been working on the necessary technology for 3 years, says Swiss Space Center Director Volker Gass. The experimental probe's potential first target would be Switzerland's first space mission, a picosatellite called SwissCube that was launched in 2009. Gass says the spacecraft, dubbed CleanSpaceOne, would cost an estimated $11 million to build and launch and could be ready between 2015 and 2017.
Space junk is an increasing problem for space agencies. It ranges in size from entire satellites that are uncontrolled to rocket stages or fragments from collisions. NASA tracks some 16,000 objects larger than 10 cm, but there are many more fragments smaller than this. Despite the objects' small size, their velocity gives them the ability to do a lot of damage.
In 2009, an operational Iridium mobile communications satellite collided with a redundant Russian communications satellite at a relative speed of more than 42,000 km per hour. NASA estimated that the crash created as many as 1000 new fragments larger than 10 cm and many smaller ones. The debris can also put astronauts at risk. The International Space Station often has to maneuver to avoid space junk, with its residents sometimes taking shelter in the escape capsule.
CleanSpaceOne is designed to take down larger pieces of junk. The semiautomatic probe will need a sophisticated guidance and control system to insert itself into the right orbit to reach a target moving at 28,000 km/h. Cameras will be used to optically identify the target satellite and ion microthrusters will ease the probe right up to it. The Swiss researchers are investigating biologically inspired gripping mechanisms to snag the target, such as one that has tentacles like a sea anemone.
Once captured, the combined object will have a new center of gravity and may be spinning in an uncontrolled way. The probe has to stabilize the trajectory and then guide itself onto a curve toward the atmosphere. "There are quite some challenges," says Gass.
Gass envisages a whole family of ready-made craft able to de-orbit different sorts of satellites. Another approach would be to sell "de-orbit kits" to be built into new satellites so that they could bring themselves down at the end of their useful lives. "Switzerland is a country that likes to keep things clean," Gass says. "So we decided to first get our own satellite down."