CALL it Junk FM. Rogue signals from your radio may help warn about space debris on a dangerous collision course with Earth. As New Scientist went to press, astronomers at the Murchison Widefield Array radio telescope in Western Australia were analysing the results of a trial to see whether stray FM signals from radios, bouncing back off space junk, could allow them to track the whole population of space debris. The MWA is a set of some 2000 radio antennas spread out over 3 kilometres. The team used these to pick up rebounding FM signals and track the International Space Station. If it works, the technique should be easy to scale down to objects as small as 10 centimetres, says Steven Tingay, director of the MWA at Curtin University in Western Australia. “We could almost get the whole population of space debris,” he says. And if it fails?