The shuttle undocked as the two craft soared more than 200 miles above the Atlantic, just west of Africa's Western Sahara.

The two crews spent 10 days together, working to install a new room, called Tranquillity, and a domed observation deck the likes of which had never been seen before in orbit. The compartments represented the last of the space station's major building blocks.

Mission Control told the six shuttle astronauts that they had had "an absolutely awesome mission" but now it was time to say "goodbye station, hello Earth!".

The shuttle is due to touch down in Florida early on Monday morning GMT.

"It's been good having you. Sorry to see you guys leave," space station resident Timothy "TJ" Creamer called out as Endeavour backed away. "We're sorry to go," replied shuttle commander George Zamka. "Hope you get to enjoy Tranquillity and the new view."

The seven windows in the space station's new lookout were shuttered before Endeavour's departure, to protect against thruster contamination. The shuttle astronauts took one last long look out those windows before retreating into their ship to prepare for the undocking. Endeavour then took a slow lap around the orbiting complex for picture-taking.

"God speed guys," radioed the space station's skipper, Jeffrey Williams.

Thanks to Endeavour and its crew, the space station is now 98% complete, with a mass of 800,000lbs. The two new compartments - worth more than £258 million - were supplied by the European Space Agency.

Only four shuttle flights remain. Discovery is up next. It will carry up more supplies and science experiments in early April. Nasa intends to wrap up what little space station assembly is left this year. It will coincide with the retirement of the three remaining shuttles.