"Endeavour, we have physical separation", a Nasa official said as the shuttle undocked from the space station some 340km above the Indian Ocean.


Endeavour's stay at the space station was the longest so far by any shuttle mission.


Nasa has an ambitious schedule of launches in the coming months as the space agency works to complete construction of the ISS by the time it retires its fleet of three shuttles in 2010.


Kibo: Japan's space lab

Last and largest of four research modules for International Space Station


Japan's first permanent manned presence in space


To be delivered into orbit by three shuttle flights


Scheduled completion in May 2008


Will conduct experiments on effect of microgravity


Includes platform with robotic arm to expose experiments to space

The Endeavour crew's main task was to install the first part of the Japanese Kibo lab, a micro-gravity research facility that will be the station's largest module when completed in March next year.


"At this moment, the people of Japan are very excited about the module," said Japanese astronaut Takao Doi, who is to return to Earth on board Endeavour.


"It is going to open up a new era for Japan in the space program."


The now-installed first component of Kibo will serve as a storage chamber with the main component, an 11 metre-long bus-sized module, due to launch aboard the shuttle Discovery on May 25.


During the mission the shuttle crew also attached the Canadian-built Dextre robot arm to the outside of the space station, installed science experiments and inspected a broken joint in one of the station's solar panels.


Endeavour is expected to return to Earth on Wednesday evening, landing at the Kennedy space centre in Florida after a total of 16 days in space.