Discovery has successfully undocked from the International Space Stationas it gears up for its return to earth after NASA declared the spacecraft fit to fly. The crew’s first mission is to fly around and take photos of the ISS for inspection by NASA engineers. The shuttle must then position itself for its potentially precarious return to earth. In a mission first, astronaut Stephen Robinson had to carry out a six-hour space walk to repair damage the shuttle’s heat-shield sustained during take off. It was caused by flying debris, something which led to the deadly Colombia disaster in February 2003 causing the shuttle to break apart on its re-entry into the Earth’s atmosphere. Nasa says Discovery is in pristine condition.