In 2010, the planetary defence team at NASA had identified and logged 90 per cent of the asteroids near Earth measuring 1km wide.It may sound like a plot from a film, and it was the subject of the 1998 film Armageddon, but the Hypervelocity Asteroid Mitigation Mission for Emergency Response (HAMMER) is a genuine NASA proposal.Whether NASA can find the remaining middle-sized NEOs depends on getting the money to build NEOCam, a 0.5-metre space telescope which would use infrared light to locate asteroids.