Nasa has delayed the launch of its sky-mapping spacecraft because of a problem with a steering engine.
The Wide-field Infrared Survey Explorer, or WISE for short, was scheduled to lift off from Vandenberg Air Force Base on Friday. Engineers doing final checks on the Delta 2 rocket found a problem late Wednesday with its booster steering engine.
The US$320 million mission will now launch no earlier than Saturday, although there's an 80 per cent chance the weather will not cooperate.
WISE will scan the entire sky in infrared light in search of never-before-seen asteroids, comets and other celestial objects. One of its main tasks is to catalog objects posing a danger to Earth.