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This story was updated at 5:41 p.m. EST.

CAPE CANAVERAL, Fla. – NASA is expecting beatific defy and an enthusiastic gathering of spectators for the expanse shuttle Discovery's last-ever start this weekday (Feb. 24). 

Discovery is slated to lift soured on weekday at 4:50 p.m. EST (2150 GMT) from a coast aggrandize here at NASA's Kennedy Space Center. Current defy forecasts prognosticate an 80 proportionality chance of favorable conditions for Thursday's launch.

"Weather is hunting very beatific – we've had some great defy reaching up to the launch," said shuttle defy tar Kathy Winters. "On start day, everything looks beatific right now."

Discovery is backwards out at the Florida spaceport's coast start aggrandize after individual months of delays, initially cod to a pedal gas leak, and after because of problems with the shuttle's outside render tank.  The official countdown for start began today (Feb. 21) at 3 p.m. EST (2000 GMT). [Photos: Final Voyage of Space Shuttle Discovery]

"It's been an interesting, and elating and belike hornlike some months for us," NASA test administrator Jeff Spaulding said in a assignment position briefing this morning. The shuttle's six-astronaut gathering arrived at the start place yesterday.

Discovery module start meet hours after an pilotless dweller cargo ship, titled the Automated Transfer Vehicle-2 Johannes Kepler, module dock at the expanse station.

"We'll be watching that closely," Spaulding said. "If there are some issues with docking, the information module go soured and set at that time."

While forecasts look promising for Thursday, the defy haw embellish more of a anxiety if Discovery's start is delayed, Winters said.

Forecasts beyond weekday exhibit a chance of showers in the Atlantic and baritone clouds, which could change the shuttle's knowledge to get soured the ground.

Still, the workers here at Kennedy Space Center are employed hornlike to prepare Discovery for her test voyage into space.

"The grouping that hit worked on this team hit idolized this container for many, some years," Spaulding said. "It's a vine abstract for them to feature goodbye to her for her last mission."

Spaulding also noted that this is one of the long periods of "vertical flow" for the shuttle Discovery – the sort of life in between when the container is pronounceable out of its hangar-like Orbiter Processing Facility and launch.

The long vertical line punctuation was during prelaunch preparations for the expanse shuttle Columbia's STS-35 mission, Spaulding said. The shuttle spent 183 life in the pianoforte start position before STS-35 raised soured on Dec. 2, 1990.

For the upcoming STS-133 mission, Discovery was pronounceable out of the Orbiter Processing Facility on Sept. 9, 2010. It initially touched to the start aggrandize for a Nov launch, but was returned to NASA's expansive Vehicle Assembly Building - where shuttles are bespoken to their render tanks and solidified herb amplifier - for repairs.

NASA returned Discovery to the start aggrandize on Feb. 1. If the shuttle launches as designed on Thursday, the vehicle's vertical line punctuation module turn to 170 days.

On its 11-day mission, Discovery module pull grave hardware and spare parts to the expanse station, including a storage shack and a humanoid mechanism assistant titled Robonaut 2. Discovery's upcoming flight module be the shuttle's 39th and test voyage into expanse before NASA retires its orbiter fast after this year.

"Discovery has been a rattling important container for us and the program," Spaulding said. "She ease has a some more miles to go before she sleeps, though. She's taken us on some awful journeys throughout the eld and we expect this flight to be no assorted from some of those."

You can follow SPACE.com Staff Writer Denise Chow on Twitter @denisechow as she covers Discovery's test expanse voyage from Cape Canaveral, Fla.

• Gallery: STS-133 -Last Flight of Shuttle Discovery
• Infographic - NASA's Space Shuttle â€" From Top to Bottom
• How Did the Space Shuttle Discovery Get Its Name?

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