The Swiss Space Center at the Swiss Federal Institute for Technology in Lausanne (EPFL), Switzerland, have designed a “janitor satellite” to help clean up the growing problem of space junk. The US$11million (10 million Swiss Francs) CleanSpace One satellite is a prototype for what they hope to be a family of satellites that are sent to retrieve large, defunct satellites and de-orbit them – making them burn-up in Earth’s atmosphere or splash down in an ocean.
NASA tracks 16,000 pieces of space junk larger than 4 inch (10.2cm) in diameter, but in reality the U.S. space agency estimates that over 500,000 pieces of space junk is up there, consisting of spent rocket stages and broken satellites. The debris orbital velocity is around 28,000 km/h (mph), and even the tiniest of particles can damage spacecraft or impact other debris, splitting it into ever-smaller pieces.
Known trash impacts include a French satellite damaged in 1996 by a rocket casing, and an U.S. Iridium Communications Satellite that was destroyed in 2009 in a collision with a defunct Russian satellite. The Iridium Satellites are in low earth orbit constellations, occupying the same orbital path so this debris will eventually spread around the Earth, affecting the other Iridium Satellites.
The CleanSpace One satellite is being built to solve three problems, such as how to maneuver a spacecraft into the same orbital path as the debris, so EPFL are developing a compact propulsion system for their small satellite (actually a 3 cube Cubesat). The next problem, after catching up with the debris, is to capture it and hold it but without creating even more debris. This could be very difficult, especially if the debris is spinning and for inspiration the researchers are looking at how plants and animals capture their prey. Finally, it has to slow the debris down and drag it into Earth’s atmosphere. CleanSpace One is going to try and de-orbit Switzerland’s first orbiting satellite, the Swisscube Picosatellite launched in 2009, or the second TIsat, launched in July 2010.
Volker Gass, The Swiss Space Center’s director hopes to someday “offer and sell a whole family of ready-made systems, designed as sustainably as possible, that are able to de-orbit several different kinds of satellites.”
One of the problems of increasing debris, apart from the risk to satellites, and any human launches or space stations, is the increasing cost of insurance. A new, US$150-500million satellite could be launched into orbit and then get knocked out of service by a $0.30 steel bolt or even a flake of paint.
The Swiss Re Insurance Company estimated that every year, there is almost a one in 10,000 chance that a 107sq.ft. (10sq.m.) satellite traveling in a sun-synchronous low earth orbit 373-621 mile (600-1,000km) will get hit by a 0.16sq.inch (sq.cm.) piece of space junk. So, if there are continuously 1000 spacecraft in this orbit, and they stay there for 10 years, there is a certainty that at least one of them will get hit over a 10-year period.
The European Union and United States hope to agree to internationally binding agreements to limit future space debris, ensuring that what goes up does eventually come down safely and efficiently without having to wait thousands or tens of thousands of years for the trash to come down by itself.
Trevor Williams is a University of Victoria Mechanical Engineering PhD candidate specializing in renewable energy, power grid modeling and plug-in hybrid electric vehicles. He has a bachelors in Aeronautical Engineering, a Masters in Management Science and over 23 years international experience in the space industry, having worked on Earth observation and telecommunications satellites. He is the author of the Eco-Geek blog.