Live In Orbit: Big Day For Space Exploration

Discovery's astronauts aim to land at Kennedy Space Center today and a new expedition crew, along with a space tourist, are scheduled to arrive at the International Space Station.

Flying in a Soyuz spacecraft, Russian cosmonaut Gennady Padalka, U.S. astronaut Michael Barratt and billionaire software developer Charles Simonyi are expected to dock at the space station about 9:14 a.m.

We'll have live coverage of the arrival starting at 8:45 a.m., and you can also see coverage of a 12:10 p.m. hatch opening and welcome ceremony at starting at 11:45 a.m. And of course you can watch coverage of the ongoing Discovery mission as the astronauts prepare to start a supersonic dive back through the atmosphere at 12:33 p.m. and the land on Runway 15 at KSC at 1:39 p.m.

Take a look at the full schedule here in this latest revision -- Rev S -- of the STS-119 NASA TV Schedule.

Discovery's astronauts will wake up at 5:13 a.m. EDT, and then deorbit preparations will begin at 8:33 a.m. The shuttle's payload bay doors are scheduled to be closed at 9:53 a.m.

Should weather or technical problems prompt NASA flight directors to keep Discovery aloft, a second and last landing opportunity of the day will come at 3:14 p.m. at KSC.

The weather forecast for landing is pretty good.

Spaceflight meteorologists expect scattered clouds 5,000 above the KSC landing strip. There is a slight chance the clouds could build up enough to block the view of the runway on final approach.

NASA in that case would be forced to forego landing, and the weather is expected to degrade significant on Sunday at KSC at two back-up landing sites: Edwards Air Force Base in California and Northrup Strip at White Sands Space Harbor in New Mexico.

"We'll keep our fingers crossed," Discovery commander Lee Archambault said Friday.

A landing on the first opportunity would come on Discovery's 201st lap around the planet -- 12 days, 17 hours and 56 minutes after its March 15 launch.

Touchdown would wind up a successful mission to complete assembly of the International Space Station's central truss and deliver a fourth and final set of massive American solar wings.

The forecast for KSC on Sunday calls for a chance of electrically charged clouds, low cloud ceilings, thunderstorms and high crosswinds.

Stiff crosswinds are forecast at Edwards that day and gusting winds would present a problem at Northrup Strip.

NASA entry flight director Richard Jones said the shuttle would be able to stay in orbit until Tuesday if need be. The limiting consumable onboard is lithium hydroxide, which is used to absorb carbon dioxide in the shuttle's crew cabin.

Jones said NASA would not call up back-up landing sites unless weather or technical problems prevent a landing at KSC on Saturday and Sunday. In that case NASA would staff KSC, Edwards and White Sands.

The weather at KSC on Monday is expected to acceptable for landing.

ABOUT THE IMAGES: Click to enlarge the long-range, mid-range and short-range ground tracks for an atmospheric reentry and landing on the shuttle's 201st orbit of Earth.