Discovery is ready to leave the International Space Station for the last time. The space shuttle is due to undock Monday morning. It won't land until Wednesday, according to a report of the Associated Press.This is the final voyage for Discovery, the most traveled spaceship ever. It will be retired after this mission and sent to a museum. Discovery and its crew of six spent more than a week at the space station, installing a new storage unit and an equipment platform. Mission Control, meanwhile, is monitoring a piece of space junk that's threatening to come too close to the station. Experts will decide following Monday's undocking whether the station will need to move out of harm's way. The debris is an old rocket piece.