CAPE CANAVERAL, Fla. ? NASA is preparing the space shuttleDiscovery to launch on one final mission today (Nov. 4) to end its 26-yearspaceflying career. But the weather is not on the shuttle's side.
Discovery, NASA's workhorse orbiter, is due to blast off at3:29 p.m. EDT (1929 GMT) from the seaside Launch Pad 39A here at Kennedy SpaceCenter. The mission has already been delayed several days due to last-minuteglitches, and faces an 80 percent chance of bad weather for today's launchattempt.
Still, with NASA's shuttle fleet set to retire next year,today's launch attempt will be the beginning of the end for Discovery. The shuttleis making its 39th and last spaceflight with this launch and is the first ofNASA's three shuttles to be retired. [GRAPHIC:NASA's Space Shuttle ? From Top to Bottom]
"There's a lot of excitement in the air," NASAtest director Scott Payne said in a preflight briefing.
Discovery is NASA'soldest space shuttle currently in service, and will embark on one finalmission to haul critical spare parts to the station, as well as a storage roommodule and a humanoidrobot to assist the crew of the orbiting laboratory.
Discovery's historic finalliftoff has been delayed several days due to leaky helium and nitrogen sealsthat were found in the shuttle's aft engine section, and a last-minute electricalanomaly in a backup computer controller in one of Discovery's main engines.
Engineering teams were able toaddress the problems in time for Discovery to make its final ascent to theInternational Space Station later today.
The weather, however, is iffy for launch. Current forecasts predicta mere 20 percent chance of favorable conditions in the area, with the biggestthreats being showers and thunderstorms near the launch site.
If bad weather preventsDiscovery's launch today, NASA could try again on Friday. The space agency hasuntil Sunday, Nov. 7 ? and possibly Monday ? to fly Discovery before itscurrent launch window closes.
The shuttle's final six-astronautSTS-133 crew is made up of commander Steve Lindsey, pilot Eric Boe, andmission specialists Alvin Drew, Tim Kopra, Michael Barratt and Nicole Stott.
Discovery's 11-day mission will include two spacewalks,during which mission specialists Drew and Kopra will perform maintenance taskson the exterior of the station.
Discovery's STS-133 mission will be the orbiter's finalvoyage into space beforebeing retired along with the rest of the NASA's shuttle fleet next year.
"It's a remarkable team that gets her ready tofly," Payne said. "They put their heart and soul into this one. Theyknow it's her last flight. She's now poised to take to the skies, and when shegoes, she's going to take a little bit of every one of us with her."
- GRAPHIC: NASA's Space Shuttle ? From Top to Bottom
- Gallery: Building Space Shuttle Discovery
- Video ? Space Shuttle Discovery: A Retrospective, Part 2, Part 3
Follow SPACE.com Staff Writer Denise Chow onTwitter @denisechow asshe covers Discovery's final space voyage from Cape Canaveral, Fla. Click here formission updates, new stories and a link to NASA's live webcast coverage.