hello and welcome. final preparations are taking place for a space mission to test the technology needed to knock an asteroid off a collision course with earth. the nasa project, scheduled to lift off in about 75 minutes from now, will target an asteroid called diamorphos which is more than eleven million kilometres away and poses no threat. our science correspondent, rebecca morelle has more. until now, it s been the stuff of hollywood blockbusters like armageddon. an asteroid heading for earth and a mission to stop it. but science fiction is becoming science fact. for the first time, nasa is sending up a spacecraft to knock an asteroid off course. this one is not a danger to the earth, but the dart