An astronaut from the space shuttle Atlantis collapsed twice Friday during a welcome home ceremony, a wobbly return that officials attributed to the adjustment from 12 days at zero gravity.

Heidemarie Stefanyshyn-Piper left the hangar at Ellington Field through a side door but was not taken to a hospital. Officials said she was doing fine.

Piper, fifth of the six astronauts to speak, appeared to be confused before her legs buckled during her address.

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NASA officials and crew members braced her and lowered her to the ground. She stood up again, and the crowd applauded.

"Boy, if that's not a little embarrassing," she said.

After speaking for another half-minute or so, she again appeared confused and gripped the podium. Crew members stepped to her side and lowered her to the floor.

Two NASA officials helped her leave through a side door.

The Atlantis crew returned Thursday after performing the first construction work on the international space station since the Columbia disaster 3½ years ago.

They performed three grueling spacewalks to hook up a 17½-ton addition, which included a giant set of electricity-producing solar panels.

Piper, a 43-year-old from St. Paul, Minn., is a commander in the Navy and was a mission specialist and cosmic electrician aboard the shuttle.

She carried out two of the spacewalks, joining an elite club of only six other U.S. women and a single Russian woman who have made spacewalks.