Astronauts pack up on next-to-last shuttle flight

The space shuttle and its crew of six will depart the International Space Station late Sunday night. They worked to repair one of the space station's air purifiers and straightened out the suits that were used in four spacewalks. The final spacewalk of the mission, on Friday, completed the U.S. portion of station construction.

Now that the spacewalks are over, Mission Control told the astronauts they "can bask in the glow of a job well done."

Shuttle pilot Gregory Johnson said it will be bittersweet to leave. He and his crewmates installed a $2 billion physics experiment at the orbiting outpost, as well as an extension pole and a platform full of spare parts.

"It's been a fantastic mission," Johnson said in a series of news interviews. "It's the sort of mission that astronauts dream of having."

Johnson said he and his colleagues are spending their final hours at the space station doing "everything we can do to help the space station out before we return to Earth." The station is so big now, he said, that sometimes he takes a wrong turn and finds himself in the wrong chamber.

Endeavour is scheduled to return to Florida before dawn Wednesday, 16 days after blasting off.

After Sunday night's undocking, Johnson will guide Endeavour through a victory lap around the space station. He said he'll try to maintain a good position for the shuttle, "so we can get great photos of one of the final fly-arounds of the space station." The shuttle crew also will test out an experimental navigation system for future spacecraft.

This is the final voyage of Endeavour, the youngest in the shuttle fleet. NASA is closing down the shuttle program this summer after 30 years. Atlantis will fly one last time to the space station in July.

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