On 11 January 2007, the People's Liberation Army destroyed an ailing Chinese weather satellite with a ballistic missile. The spacecraft was blown to smithereens, ejecting thousands of shards of debris into space. Since then the junk has been spreading out in mid and low-Earth orbits, a hazard to the evergrowing numbers of spacecraft plying those orbits. No one knows why this cosmic vandalism took place because Beijing has remained tight-lipped on the issue: old satellites are normally brought down safely over the broad expanse of the Pacific Ocean, or else parked in a graveyard orbit, deeper in space, expending the last of their fuel to get there. But the incident throws into sharp relief what happens when just one spacecraft breaks up. "It creates a cloud of debris composed of thousands of small fragments," says Richard DalBello of Intelsat, a satellite operator in Bethesda, Maryland. With the era of mass space tourism approaching, and more satellites being launched into the heavens, for global positioning, telecommunications and Earth monitoring, for example, the worry is that spacecraft will collide with the debris from old satellites, rocket stages and thernlike, potentially risking lives and serious damage to multimillion-dollar space vehicles. Right now, spacecraft follow a carefully synchronised dance in orbit, using signals from ground controllers, who track known debris, to dodge any hypersonic junk. For instance, just two weeks ago the International Space Station had to be shifted to avoid debris. But the sheer volume of stuff in orbit will soon make it difficult to manoeuvre spacecraft without risking an accident. "We do not have clear rules of the road," admits Vladimir Agapov of the Russian Academy of Sciences in Moscow. "Close and sometimes dangerous operations are now common in some orbits."
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