Space shuttle Endeavour arrived at its launch pad early Wednesday for a flight to deliver teacher-turned-astronaut Barbara Morgan and six crewmates to the international space station.

It's been a nearly five-year wait for Endeavour, and the shuttle has nothing on Morgan: She's been waiting 22 years.

In 1985, Morgan was picked as Christa McAuliffe's backup to become the first teacher in space under a special NASA program.

Then the shuttle Challenger carrying McAuliffe broke apart shortly after liftoff in 1986, and Morgan returned to teaching.

In 1998, she was selected as a full-fledged astronaut.

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On her first mission, set for August, Morgan will operate the shuttle's robotic arm, coordinate the transfer of cargo and talk from space to students at three schools, if the mission is extended.

Talking to students and teachers Wednesday morning, Morgan said she was most looking forward to seeing McCall, Idaho — where she taught elementary students — from space. She said the Endeavour crew was training hard during their last few weeks before launch.

"There's a ton of work to be done," Morgan said during the forum at the Johnson Space Center.

The shuttle crew will deliver a new truss segment, 5,000 pounds of cargo and fix a gyroscope which helps control the station's position. It also plans four spacewalks if the mission is extended to 14 days.

"It has a little bit of everything," said Matt Abbott, lead shuttle flight director.

Endeavour's 3.4-mile journey aboard the massive crawler-transporter from the Vehicle Assembly Building took seven hours, getting the shuttle to its launch pad shortly after 3 a.m. It was a day late because the weather had nixed plans to move it early Tuesday.

Its launch is scheduled for Aug. 7 as NASA's second shuttle flight this year.

The last time Endeavour was at the launch pad was in November 2002, before its launch on a construction mission to the space station. It was the last shuttle flight before the Columbia disaster killed seven astronauts and grounded the space shuttle program for 2½ years.

Endeavour has since undergone a major tune-up. The shuttle's structure was inspected for corrosion. Filter and seals were replaced. More than 1,900 thermal blankets were examined, and two windows were replaced with thicker panes.

"We're really excited to have Endeavour fly again," Kim Doering, NASA's deputy manager of the space shuttle program, said Tuesday. "Obviously, having brand new belts and hoses and having just checked the structure and replaced all the tiles — they're brand new — makes this a very nice vehicle to climb on to."

Endeavour also has a new system which allows power from the space station to be transferred to the shuttle while docked. If the new system works properly, the 11-day mission will be extended by an extra three days.