Removing space junk

HUMAN BEINGSAGI are messy. They tend to leave rubbish behind them wherever they go—and to expect someone else to clear that rubbish up. This is true even in outer space. The problem of orbiting debris, and the concomitant risk of it colliding with and damaging an active and probably expensive satellite, has been around for a while. But it is rapidly getting worse. There may now be as many as 1m bits of debris measuring 1cm or more across in orbit. Of larger objects, more than 20,000 are being actively tracked from Earth. And, according to Daniel Oltrogge, an expert who advises the Space Data Association, an industry body, on such matters, the past three years have seen a doubling of the number of times that bits of junk have almost hit operating satellites.In the short term, satellite owners can, literally, dodge the problem—as long as their craft are fitted with appropriate thrusters. Mr Oltrogge’s day job is to arrange for that to happen, for he also works for , an American firm that develops (among other things) software which helps satellite operators sidestep such collisions. In the longer term, however, more radical action will be needed.