This story was updated at 9:45 p.m. ET.
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 as both spacecraft flew 208 miles (334 km) above the Atlantic Ocean.
The shuttle?s six-astronaut crew spent nine days at the station, where they attached the new Tranquility module and a seven-window space observation deck, which they called the ultimate ?window on the world.?
?Thanks very much for the great hospitality. We?re sorry to go,? shuttle commander George Zamka told the station crew. ?Hope you enjoy Tranquility and the new view.?
?Godspeed guys, we?ll see you back on the planet,? station commander Jeffrey Williams radioed back.
The station astronauts had to keep the shutters closed on the new observation deck?s seven windows while Endeavour departed to protect them from inadvertent damage from the shuttle?s thrusters. Mission managers said it might be possible to open the windows later, once Endeavour was far enough away.
The new lookout 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,? Zamka said before leaving the station. He 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 words?it 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 flew a victory lap around the space station before leaving the orbiting lab?s neighborhood. The maneuver allowed the shuttle astronauts to take a look at their handiwork and snap photos of the space station.
?You guys are looking absolutely marvelous down there with the backdrop of the ocean and the clouds,? Williams said he watched Endeavour below the station. Virts was 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.
NASA engineers will study the data and images from Endeavour?s upcoming inspection before clearing the shuttle and its crew for their planned weekend landing.
Endeavour?s STS-130 mission is the first of NASA?s five final shuttle missions before the space agency retires its three aging orbiters in the fall.
The shuttle and its crew are due to land Sunday night at 10:16 p.m. EST (0316 Monday GMT).