045_G17 Arena

Global_17

Arena Science debris particles. In February 2009 the Iridium 33 satellite collided accidentally with the inactive Kosmos-2251 satellite at a speed of some 42,000 km per hour, generating some 1,000 pieces of debris.” Pieces of debris that cause damage are often small, but with satellites travelling at around 28,000 km per hour, collisions, even with small objects, can be significant. Scientists compare the smallest pieces of metal to bullets, leaving holes in anything they collide with. The larger objects are constantly monitored. “Detection and tracking of space debris is done by large, high-power radars, of the same sort as are used for ballistic missile defence,” says Griffiths. “This allows a catalogue of debris objects to be maintained so that, for example, any threat to the International Space Station can be identified in advance and suitable precautions taken.” The first recorded collision of two man-made objects occurred in 1996, when a satellite owned by the French government was struck by a rocket that was also French. The satellite was made by Surrey Satellite Technology in the UK. Doug Liddle, head of science at Surrey Satellite Technology, explains: “Our satellites used to have these big booms on them, which help to point them in the right direction. Half the boom got sliced off by the French rocket! It really was a big problem at the time, but now we’re much better at tracking and providing information to the community. We get reports from a US group called the Joint Space Operations Center when we are potentially going to get hit by anything and that allows us to move if we need to. There’s room for error, but they will predict the probability of an impact, so if you’re going to be within 1,000 metres of being hit they let you know.” The risk of further collisions is not a big issue for Surrey’s satellites yet, he says, but it is a growing problem. “The difficulty comes about because some satellites have the ability to move and some don’t. If you’ve got a large piece of space junk coming towards you, you need to be able to move to get out of its way.” The only way to prevent the situation from deteriorating is to perform an almighty clear-up. This throws up the thorny question of just who is responsible for clearing up the debris. Space law has failed to keep up with the rapid development of space exploration over the last 50 years. Although space lawyers might sound like they come straight out of a sci-fi novel – and the dream job for bookish, space-loving children – the field of space law is serious and complex. In the case of the 2009 crash between the USA’s Iridium 33 communications satellite and the defunct Russian Kosmos 2251, there was no binding guidance on who was liable. Should Russia have de-orbited its satellite? Should Iridium have moved? The gap in legislation is one of the biggest problems facing the clean-up effort. So how will the international community go about this cosmicscale clean-up? As with all major tidying-up sessions, it’s best to start with the big stuff and then move on to sifting through the smaller items. The larger the item, the more debris it will create if a collision occurs, making more work in the future. The key to getting rid of the clutter is to lower the debris’ orbit so that it eventually re-enters the earth’s atmosphere, burning up as it does so. At least that is the hope. A satellite came down over the Netherlands, Germany and the Czech Republic in 2011, but no fragments were ever found. An organisation called the Inter-Agency Space Debris Coordination Committee is aiming to take the lead in the clean-up. This international advisory group has been working with each country’s space agency, asking them to act as a regulatory body for any satellite owned by that nation. The idea is that every satellite that’s launched needs to be brought back down safely at the end of its life. “Historically, people have finished using their satellite and they’ve just left it up there, switched on and still in the same orbit, There have been more than 6,000 satellites launched since Sputnik where it could stay for the next few 100 years,” explains Liddle. “The plan now is that at the end of life, once you turn your satellite off, it will come down within the next 25 years and it will hopefully burn up in the atmosphere. If you don’t think it will burn up in the atmosphere, you have to try to do a controlled re-entry so it will hit the ocean and not some poor bloke sitting in his flat in London. But not many spacecraft can do a controlled re-entry because you need to have a really hefty propulsion system. Another option that a lot of people are using is to incorporate drag sails and make the surface area as big as possible.” We get reports from a US group when we are potentially going to get hit by anything and that allows us to move Although awareness of space junk is growing outside the scientific community, the majority of people who rely on satellites for services like phone or internet money transfer and remote working – essentially modern life – have no idea that the technology upon which they unconsciously rely may not be able to continue in its present format if the issue of cosmic debris isn’t addressed. Doug Liddle puts the dilemma into a nutshell: “If we don’t find a way to resolve it, we’re going to spend an awful lot more money tracking debris and satellites will constantly have to manoeuvre around it. It’s going to be like crossing a really busy road. Up until now it’s been like a quiet country lane.” global f i rst quar ter 2014 www.global -br ief ing.org l 45


Global_17
To see the actual publication please follow the link above