The seven astronauts of the US shuttle Discovery bid farewell on 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 8.42pm GMT after the six US astronauts and their Japanese counterpart floated back inside the shuttle ahead of their departure on Wednesday morning.

Discovery will undock from the orbiting outpost at 11.42am GMT on 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 shuttle crew 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 Centre in Cape Canaveral, Florida, on Saturday at 3.14pm GMT after 14 days in space.

The shuttle delivered, opened and outfitted the 11.2-metre long, 4.4-metre 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.

AFP