WASHINGTON (AFP) - The seven astronauts of the US shuttle Discovery bid farewell Tuesday to their three colleagues at the International Space Station after a busy mission to install Japan's first space laboratory. The hatches between the two spacecraft were shut at 2042 GMT after the six US astronauts and their Japanese counterpart floated back inside the shuttle ahead of their departure Wednesday morning. Discovery will undock from the orbiting outpost at 1142 GMT Wednesday following a 10-day mission that expanded the station with the addition of Japan's bus-sized Kibo lab. The shuttle also brought a new crew member to the station, Greg Chamitoff, who replaced fellow American astronaut Garrett Reisman, who is returning to Earth aboard Discovery after a three-month stint at the outpost. After leaving the station, the shuttlecrew will use the orbiter's robotic arm to scan its heat shield for signs of any potential damage from space debris or micrometeorites. Discovery is scheduled to land at the Kennedy Space Center in Cape Canaveral, Florida, on Saturday at 1514 GMT after 14 days in space. The shuttle delivered, opened and outfitted the 11.2-meter (36.7-feet) long, 4.4-meter (14.4-foot) wide Kibo module last week. The mission also included three spacewalks. The Japanese lab is the largest facility of the space station, which includes modules from the United States, Russia and European Space Agency. NASA, which hopes to complete construction of the station by 2010, considers the station a central part of space exploration ambitions, allowing scientists to study the effects of microgravity on humans.