Morgan was hired when she was 34 to stand in if needed for a fellow teacher, Christa McAuliffe, in the 1986 mission which would have made McAuliffe the first teacher in space.

But the mission was cut violently short. The Challenger exploded 73 seconds after take-off on January 28, 1986 due to a faulty booster rocket, killing McAuliffe and Challenger's six other crew members.

Now Morgan is stepping up to the challenge, as one of five "mission specialists" on the shuttle Endeavour when it shoots off Wednesday for the International Space Station.

"I know people will be looking at this and remembering Challenger, and that's a good thing," she said in an interview released by the US National Aeronautics and Space Administration (NASA).

"They will also be thinking about all the people -- teachers and other people -- who have been working really hard ... to carry on the work that Christa was doing. I'm happy about that."

Morgan, now 55, trained alongside McAuliffe ahead of the Challenger mission after they were chosen from thousands of teachers as "Educator Astronauts."

The job aimed to bring back insights into the world of space exploration to school children and students on Earth and boost public interest in NASA's space program.

Morgan started out as a mathematics and reading teacher at an elementary school in a native American reservation in Montana. She resumed school teaching after the Challenger disaster before starting two years of training as a NASA mission specialist in 1998.

When Endeavour lifts off from the Kennedy Space Center in Florida on Wednesday, she will find herself on an 11-day mission to help develop the space station as a potential stepping stone to exploration of the planet Mars.

Among her duties will be operating robotic arms to unload and install new equipment and supplies on the station.

NASA hesitated for years to send another teacher on a mission after the Challenger disaster.

It was the first space catastrophe for the United States. McAuliffe's death as a crew member from a civilian background added poignancy to the Challenger disaster, witnessed by schools and households as it was broadcast live on television.

Crews used to be composed only of military test pilots, but Morgan's astronaut training at the agency makes her qualified to serve as a mission specialist alongside scientists and engineers.

In 2003, the Columbia shuttle repeated the grim fate of the Challenger. Safety was urgently reviewed after the Columbia explosion, which killed all seven crew members.

"Our kids are concerned about the risk of course, as is my husband, as anyone would be. But, they know this is important," Morgan said. "They want to fly too."

In a broadcast from the space station she is due to answer questions from school children in the western state of Idaho. "Astronauts and teachers learn and share, they discover," she said. "That's what this is all about."

McAuliffe on her mission had been due to teach classes from space, but Morgan's duties will not leave her time to do that.

"Christa was, is, and always will be our 'Teacher in Space,' our first teacher to fly" in a shuttle, Morgan said.

"She truly knew what this was all about -- not just bringing the world to her classroom, but also helping ... to show the world what teachers do."

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