Nasa scientists have been inspecting damage caused to the space shuttle Atlantis after it was hit by debris during launch this week. Astronauts uncovered a half-metre stretch of nicks on the shuttle's tiles, but Nasa said the damage did not appear to be serious. It is thought the damage was caused by debris that came off the fuel tank shortly after lift off on Monday. "The damage itself appears to be relatively shallow and it's not a very large area of damage," deputy shuttle program manager LeRoy Cain said. The shuttle is on its way to the Hubble Space Telescope - a risky mission as the Hubble's orbit if littered with debris. Even before damage was discovered, Nasa was preparing shuttle Endeavour to rush to the astronauts' rescue if needed. The astronauts will capture the observatory and, the next day, begin the first of five gruelling spacewalks to install new cameras and equipment and repair some broken science instruments. Damage to the shuttle during lift-off has been a worry since Columbia was doomed by a chunk of fuel-tank insulating foam that broke off during launch in 2003.