The American space agency NASA is planning to launch a new mission to Jupiter in a few hours time. The un-manned solar powered spacecraft called Juno will take five years to reach the planet, the largest in the solar system.The project's chief scientist said the probe was just part of NASA's exploration programme. Juno is the second in Nasa's so called New Frontiers class missions. The first, New Horizons, was launched towards dwarf planet Pluto in 2006 and should arrive at its target in 2015.