SPACE.com will carry NASA TV launch coverage beginning at 2 p.m. EDT (18:00 GMT).

The weather outlook, however, is a bit pessimistic. Forecasters say there is a 70 percent chance that stiff crosswinds or low-level clouds at KSC's shuttle runway could force another delay in the flight, which originally was slated to take off last Thursday.

Strict NASA flight rules call for a launch attempt to be cancelled if crosswinds at the runway top 17.25 miles per hour (27.6 kilometers per hour).

The reason: Gusty crosswinds could make it dangerous for a shuttle crew to attempt an emergency landing if major problems cropped up early in flight.

The potential for thick low-level clouds over the runway also will be a concern. A cloud ceiling of 5,000 feet (1,517 meters) is required to make certain a shuttle crew could see the runway on final approach in the event of an emergency landing attempt.

Despite the less-than-ideal forecast, NASA managers decided to press ahead with fuel-loading operations at KSC's launch pad 39A, where Discovery is poised for launch.

Some 528,000 gallons (2 million liters) of liquid hydrogen and liquid oxygen are being pumped into Discovery's 15-story external tank. The propellants will power the shuttle's three main engines during an 8.5-minute climb into orbit.

The start of the fuel-loading operation was delayed about an hour and 18 minutes so technicians could fix a balky signal relayer on the shuttle's mobile launcher platform, a two-story steel structure about the size of a baseball diamond.

The signal relayer plays a key role in separating the shuttle - which sits atop the platform - from fuel, gas and electrical lines when the ship's two solid rocket boosters ignite.

The way the system works, the so-called Pyrotechnic Initiation Controller sends computer commands to small explosive devices that detonate just before launch, allowing a 20,000-pound (9,000-kilogram) counterweight to fall.

The counterweight then pulls the ground umbilicals away from the shuttle before it begins a speedy climb away from the platform.

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The day ahead

Discovery's astronauts, meanwhile, woke up just after 7 a.m. EDT (11:00 GMT) and soon will start preparing to head out to the launch pad.

NASA TV coverage will include a traditional photo opportunity in the crew quarters at 2:40 p.m. EDT (18:40 GMT) as well as a live broadcast of the astronauts suiting up for flight at 3:20 p.m. EDT (19:20 GMT).

The astronauts are scheduled to depart crew quarters at 3:50 p.m. EDT (19:50 GMT) for a 12-mile (19-2-kilometer) trip out to the launch pad.

The six-man, one-woman crew will begin boarding Discovery about 4:20 p.m. EDT (20:20 GMT) and the ship's hatch will be closed for flight at 5:35 p.m. EDT (21:35 GMT).

NASA's 100th shuttle flight initially was scheduled for last Thursday but was cancelled so engineers could analyze a potential problem with a suspect bolt on the shuttle's external tank.

Magic Moments

Enjoy some of the more memorable moments during the first 100 Space Shuttle flights with this image gallery.

The need to replace a balky main propulsion system valve prompted NASA to push the planned flight back to Monday.

High winds at KSC, however, prevented NASA from finishing up key pre-launch preparations in time for fuel-loading operations, forcing yet another delay Monday.

Should the weather ground Discovery again today, conditions at KSC are expected to improve Wednesday and Thursday.

Forecasters say there are only 40 percent and 30 percent chances, respectively, that bad weather would launch delays on those days.

Once airborne, Discovery and its crew will set sail on one of the most ambitious space construction missions of all time.

The astronauts are to mount the first piece of the International Space Station's metal backbone and add a new shuttle docking port to the outpost. The job calls for the crew to carry out a quartet of spacewalks on consecutive days.

A launch tonight would lead to an Oct. 21 landing here at KSC, setting the stage for the station's first full-time crew to take up residence at the international outpost on Nov. 1.

That crew -- made up of an American astronaut and two Russian cosmonauts -- is scheduled to launch Oct. 30 from the Baikonur Cosmodrome in Kazakhstan.