Later today the space shuttle Endeavour is scheduled to take off on another construction mission to the International Space Station. This mission will also be bringing the first teacher into space since the ill-fated Challenger mission two decades ago.

Endeavour is the youngest vehicle in the shuttle fleet. It was commissioned as a replacement for Challenger, after it exploded in 1986 seconds after liftoff, killing all seven astronauts on board.

One of the Challenger victims was a schoolteacher named Christa McAuliffe.

Shuttle astronaut Barbara Morgan trains at NASA's Virtual Reality Lab

Her backup was Barbara Morgan, who was then a classroom teacher. She was a few kilometers from the launch pad, watching as the shuttle blew up.

Morgan changed careers and joined the astronaut corps in 1998, and she will be going into space for the first time this week as a mission specialist in Endeavour's seven-member crew. At a news conference recently she was asked about the message she'll be bringing to students as an astronaut-educator.

"What I would like them to do is take a good look, again, at themselves and their own curiosities and what they want to know and learn," Morgan said, "and I look forward to our students looking with pride at their own teachers and all that they do to help them get ready for the future."

Morgan will be conducting some lessons while in orbit, and she said that thanks to advances in communication technology since 1986, she'll be able to reach many more students than Christa McAuliffe could have. "Rather than one or two classrooms being able to be actively involved, we can literally have kids all over the country and Canada and the rest of the world involved as well."

Morgan is scheduled to do at least one interactive lesson with students on the ground. If the mission is extended there may be time for one or two more. But even students who won't have the opportunity to participate in an inflight lesson will have a chance take part.

"So we'll be taking up about 10 million basil seeds," she explained. "We plan on distributing those to classrooms and other education venues like science centers and scout groups, etcetera, when we return. And that's to really physically hand a gift to these kids that says, please go out and do what we get to do: go explore, go experiment, go discover."

While astronaut-educator Barbara Morgan is getting the most media attention, the main agenda of this shuttle mission is to continue construction of the International Space Station. The space shuttle crew will install a large truss section, replace a gyroscope, and deliver more than 200 kilograms of supplies, among other tasks.

In addition to their construction duties, the astronauts will keep busy with other things, too. Canadian mission specialist Dave Williams, who is a medical doctor, said one experiment he'll be doing involves testing saliva for the presence of latent viruses, which might help scientists understand how those inactive viruses become active.

"Perhaps, then, we can take that knowledge to the clinical environment and for patients who have problems with shingles, be able to detect it early on in the saliva and then treat them prophylactically with medications before they actually get a severe infection," Williams told reporters. "So I think that's a clear demonstration of one of the spinoffs of the space medical research to the clinical environment."

The shuttle Endeavour is scheduled to be in space for 11 days, but if all goes well, the mission may be extended for several more.