It is T-3 hours and counting for space shuttle Discovery. Launch remains on track for 4:50 p.m. EST. There are periodic holds or pauses scheduled during the countdown. The astronauts, led by Commander Steve Lindsey, will head out to Launch Pad 39A at NASA’s Kennedy Space Center in Florida shortly. For continuous coverage of the countdown, check out NASA’s launch blog at http://www.nasa.gov/mission_pages/shuttle/launch/launch_blog.html