With their hardest tasks behind them, space shuttle Atlantis' six astronauts got time to relax Saturday after almost a week of nonstop work adding a new 17 1/2-ton addition with wing-like solar power panels to the international space station.

NASA even let the crew sleep an extra hour before waking them with Jimmy Buffett's beach song "Twelve Volt Man."

"We said good morning to them, then a little housekeeping and then left them alone, gave them a chance to enjoy their time on orbit and wind down from what has been a very, very busy series of days on the flight," said flight director Paul Dye.

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The astronauts were grateful and echoed Dye's description.

"We've been very, very busy so the chance to sleep in was very much appreciated," rookie astronaut Heide Stefanyshyn-Piper said during a news conference from space.

Saturday was the last full day at the space station for Atlantis' crew. Besides relaxing and enjoying the view from 220 miles above Earth, they still had to unload supplies for the space station, including 90 pounds of oxygen.

The Atlantis astronauts were to say their goodbyes to the space station's three crew members and undock early Sunday. Once undocked, the crew planned to fly around the space station to get the first complete view of the orbiting space lab in several years.

"We're leaving it in an entirely different configuration than it was when we arrived," said Atlantis pilot Chris Ferguson. "So it would be very good ... to get a good look at the overall configuration and condition of the station."

The Atlantis crew delivered to the space station a 17 1/2-ton addition and, during three spacewalks, hooked up the new segment and prepared it so the 240-foot solar energy arrays could be opened up. The solar arrays will provide a quarter of the space station's electricity when it is finished in 2010.

It was the first shuttle mission devoted to space station construction since December 2002. The Columbia accident in early 2003 halted all construction while NASA worked to fix problems with the shuttles' external fuel tanks.

Contrary to appearances, this past week's spacewalks were difficult, said astronaut Joe Tanner, who went on two of the mission's three spacewalks with Stefanyshyn-Piper.

"I want to squash that bug right now," said Tanner when told by CBS News that he made the spacewalks look easy. "These (spacewalks) were not easy."

Also not easy was getting used to zero gravity for Atlantis' rookies, Ferguson and Stefanyshyn-Piper, who said they kept banging into things.

"I feel really clumsy in space," Stefanyshyn-Piper said. "Because you think ... you're going to make it from point A to point B, and you kind of go to point C, D, and E, getting to point B."

Even Tanner, 56, who had been on three previous space flights, said getting used to zero gravity again was more difficult than when he was younger.

However, despite their initial wobbliness in orbit, the crew earned high praise from the mission's flight director.

"I rate this crew 110 percent. They've done an outstanding job up to this point," Dye said. "We're not going to lose our focus until we get on the ground so we'll keep our game face on. But I suspect everything's going to keep going pretty darn well."