Live: Crew works checklist, heading for Florida landing today

The space shuttle Discovery and seven astronauts are going through their pre-landing checklists right now, aiming for a dramatic plunge back through the Earth's atmosphere a few hours from now. Activity is picking up in orbit, in Mission Control in Houston and at the Shuttle Landing Facility at the Kennedy Space Center.

The crew has begun de-orbit preparations, including aligning navigation controls. About an hour from now - a few minutes after 9 a.m. - Mission Control should give the crew the go-ahead to close Discovery's payload bay doors for re-entry. The schedule calls for the doors to be closed around 9:19 a.m. Weather reconnaissance flights are getting under way and will continue throughout the morning to aid decision-making.

At one minute before noon, if the weather looks good, Discovery will fire its manuevering engines, positioning the orbiter for re-entry and slowing the vehicle down just enough that it will begin the freefall from orbit. From there's it's about 62 minutes to wheels stop at KSC.

Discovery will fly an unusual course over British Columbia, Canada, and then entering northwest United States in Montana on a southeast heading. The spaceship will cross into Florida from the north.

The ground tracks have Commander Pam Melroy banking over the space center and making the final approach from the south. Discovery is set to touch down seconds after 1:01 p.m.

Those who want to know more about trying to see the shuttle or hear its sonic booms, can find a list of Frequently Asked Questions here.

NASA plans to bring Discovery home on a track that flies over the continental United States -- and some major population centers -- for the first time since Columbia broke apart during atmospheric re-entry in 2003 and showered debris across Texas.

After that accident, investigators prompted NASA to take a harder look at its policies for over-flying populated areas when bringing the shuttle orbiters home. The agency was not told to avoid doing so, but rather to consider the risks as part of its decision-making process in picking landing tracks. In this case, NASA says an overflight of populated areas is a non-issue because Discovery's heat-shielding and other systems appear in perfect condition for a safe, uneventful return to Earth.

You can read up on the landing weather in this earlier post. In general, conditions look great for landing today at KSC.

NASA is not activating the backup landing sites in California or New Mexico. Discovery will attempt to land at KSC at 1:01 p.m. or one orbit later at 2:36 p.m. If that doesn't work out, Discovery and crew will spend another day in space.