A giant, eight-tracked crawler-transporter has begun inching Discovery out of the 52-story Vehicle Assembly Building at Kennedy Space Center for its final planned move to a launch pad.
The "rollout" officially began around 7:30 p.m., about 30 minutes ahead of schedule.
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When the spaceship emerges from the assembly building's High Bay 3, it will be bathed in bright white xenon lights as the last daylight fades.
More than 3,000 employees and family members issued passes to watch the historic rollout are still arriving in cars, parking near the turn basin.
With the crawler-transporter rolling at a top speed of about 1 mph, Discovery's 3.4-mile move is expected to be completed around 3 a.m. Tuesday.
Discovery is heading to launch pad 39A for a targeted Nov. 1 launch to the International Space Station on its last scheduled mission.