One of the space shuttle program's earliest commanders and the first woman to live on the International Space Station took their places alongside the nation's space heroes May 7 as they were welcomed into the U.S. Astronaut Hall of Fame.

Karol "Bo" Bobko and Susan Helms joined the Hall of Fame during a ceremony at the Kennedy Space Center Visitor Complex at NASA's Kennedy Space Center in Florida. The celebration came two days after NASA marked the 50th anniversary of Alan Shepard's flight in 1961 that made him the first American in space.

Bobko flew as the pilot on STS-6, the first flight of space shuttle Challenger, in April 1983. Two years later, he commanded Discovery on STS-51D and landed the shuttle safely despite a blown main gear tire. Six months later, Bobko commanded Atlantis on its maiden flight, STS-51J.

"My wife said whenever I was given a chance, I chose the career path toward space," Bobko said. "All spaceflight is beautiful and inspiring."

The astronaut thought he would go into space a lot sooner. The Air Force chose him for its own astronaut corps in 1966 to crew the Manned Orbiting Laboratory, or MOL, a project the Air Force later canceled. Like STS-1 Pilot Bob Crippen and five others who were in the MOL program, Bobko joined NASA. He worked on the Apollo-Soyuz Test Project as a support team member before flying as a chase pilot on the shuttle prototype Enterprise landing tests.

"Bo loved spaceflight and he wanted everyone working with him to enjoy it as much as he did," said Bobko's presenter, former astronaut Jeff Hoffman. "He enjoyed flying so much that his family said they could judge how close he was getting to a flight because the smile on his face kept getting bigger and bigger and bigger."

Helms, an Air Force veteran like Bobko, flew five times on the shuttle beginning with STS-54 in January 1993. Her spaceflight career included flights on Endeavour, Discovery, Columbia, Atlantis and the International Space Station. She spent more than 5,000 hours in space, with 163 days of that on the station.

"It was one of the most amazing things that I've ever had the chance to do, which was be part of a space outpost" Helms said. "That truly was a human adventure that has no equal."

Working from Discovery, Helms performed a world-record spacewalk lasting eight hours and 56 minutes.

Endurance was kind of a trademark of Helms, said her presenter, NASA Administrator and former astronaut Charlie Bolden. She went for a jog on one occasion with her dog, Radar, and when she and the dog got back, she said the jog had gone fine. But Radar went and laid down on the bed for two days.

"She outran the dog," Bolden said.

Bobko and Helms join a group that includes the legends of Mercury, Gemini and Apollo, along with the astronauts who flew the space shuttle on some of its most noted missions.