A team of astronauts has attached a $1bn (£500m) Japanese laboratory to the International Space Station (ISS).
The 15-tonne Kibo lab was delivered by the shuttle Discovery. It will be the station's biggest room, for the study of biomedicine and material sciences.
Astronauts Akihiko Hoshide and Karen Nyberg manoeuvred Kibo into place, using the space station's robotic arm.
The lab was anchored after two crew members had made preparations during a spacewalk lasting more than six hours.
Discovery docked at the ISS on Monday after a two-day voyage.
As well as the Japanese laboratory, the shuttle has also brought a new pump for the station's toilet, which broke nearly two weeks ago.
The failure has resulted in the resident crew on the ISS having to perform manual flushes several times a day.
The lab was moved into place using a mechanical arm
The Kibo Japanese Pressurised Module (JPM) is the size of a bus and joins the US Destiny lab and the European Columbus lab which are already attached to the platform.
Kibo is so big it could not be fitted inside a single shuttle and is being assembled in three parts. A logistics module went up on the previous shuttle flight; an exposed "terrace" on which experiments can be done outside of the station will launch in 2009.
The logistics module will be moved from its current docking position to a berthing point on the JPM later in Discovery's mission. All of its contents - experimental racks and equipment - can then be moved inside the 11.2m-long cylinder to get the module ready for science.
Kibo experiments will make use of the weightless conditions experienced in orbit.
Being able to see how biological, chemical and physical systems behave in the absence of a strong gravity field will help researchers better understand how the human body works and aid their search for materials that display useful new properties.
The Discovery flight has also delivered Canadian-born astronaut Greg Chamitoff, who will replace flight engineer Garrett Reisman as a station resident for the next six months.
Discovery also carried up a VIP - the space ranger Buzz Lightyear.
The 30cm-tall (12in) action figure, made famous in the Disney/Pixar Toy Story movies, went into orbit as part of an educational programme.
Nine further shuttle flights are required to complete the ISS before the orbiter fleet is retired in 2010.
Discovery's return to Earth is scheduled for 14 June.
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