NASA's space shuttle Endeavour cast off from the International Space Station late Friday, capping more than a week of orbital construction to add a phenomenal new lookout dome and room to the orbiting lab.

Endeavour undocked just before 8 p.m. EST (0100 Saturday GMT) to begin the two-day trip back to Earth. The shuttle's six-astronaut crew spent about nine days at the station to attach a new module and a seven-window space observation deck, which they called the ultimate "window on the world."

"We're really going to enjoy the view," station commander Jeffrey Williams told the shuttle crew late Thursday. "I wish you guys could stay a little longer to partake in that view."

Endeavour's crew said it was time to go home, but agreed about the station's stunning new lookout, which includes a huge round portal that is 31 inches (80 cm) wide – the largest space window ever built.

"It's tough to turn away from that window," said shuttle skipper George Zamka.

Zamka and his crew are due to return to Earth Sunday night to end their two-week mission with a landing at NASA's Kennedy Space Center in Florida.

There are several opportunities for skywatchers on Earth to see the space station and Endeavour this weekend as they fly in tandem across the night sky. [How to spot the shuttle and space station.]

Room with a view

Endeavour blasted off Feb. 8 carrying the space station's new Tranquility module and the lookout dome, called the Cupola.

"You have had an absolutely awesome mission, but now it is time to say good-by station, hello Earth!" Mission Control told the shuttle crew today in a morning message.

Tranquility is a nearly 24-foot (7-meter) long room attached to the left side of the station's central Unity module. It is named after NASA's historic Apollo 11 moon base and will serve as the station's gym, robotic arm control center and life support system hub.

Mission Control gave Endeavour's astronauts an extra day docked at the space station so they could finish up work to move urine and water recycling equipment into Tranquility. The robotic arm workstation will be moved later after the shuttle mission, NASA officials said.

The Cupola lookout is the crown jewel of the space station. The window-lined dome is about 10 feet (3 meters) wide and 5 feet (1.5 meters) deep. Its central round window points directly at Earth, with the six others arranged in a circle for a phenomenal, 360-degree panoramic view.

"Getting to look out the shuttle windows and the station windows has been awesome," Endeavour pilot Terry Virts told reporters late Thursday. "But when we looked out the Cupola, it's impossible to put into took my breath away."

The two new additions took three spacewalks to install. They were built in Italy for NASA by the European Space Agency and together cost nearly $409 million.

With them installed on the space station, the $100 billion orbiting lab is now 98 percent complete after more than 11 years of space construction. The station also weighs nearly 800,000 pounds (362,873 kg) and is the product of cooperation among 16 different countries.

It now has a dozen rooms, counting the small Cupola.

The astronauts also had time for some levity at the space station. During their free time, they took a cosmic phone call from President Barack Obama and held an impromptu Winter Olympics in space.

Space victory lap

Endeavour will fly a victory lap around the space station before leaving the orbiting lab's neighborhood.

The fly-around maneuver will allow the shuttle astronauts to take a look at their handiwork and snap photos of the space station. Virts will be at Endeavour's controls during the maneuver.

Mission Control asked the spaceflyers to take pictures of a Russian Soyuz spacecraft also docked at the space station. Part of an insulation blanket on that spaceship appeared loose or wrinkled and Russian engineers hoped for better views, mission managers said.

Endeavour astronauts will also conduct one last inspection of their spacecraft's fragile heat shield. The survey, a standard chore since the 2003 Columbia tragedy, will use Endeavour's robotic arm and a 50-foot (15-meter) inspection pole to look for any damage to the shuttle's wings edges and nose cap while it's been in space.

The astronauts performed a similar scan just after launch to look for any damage caused by fuel tank debris during liftoff, but Endeavour's heat shield was perfectly healthy, mission managers said.

A piece of fuel tank foam damaged the shuttle Columbia's wing during its 2003 launch, leading to its destruction and the loss of seven astronauts during re-entry.