Launch controllers took their posts at about 2:30 p.m. EST for Discovery's mission to the International Space Station.

In Firing Room-4 in the Launch Control Center at NASA's Kennedy Space Center in Florida, launch controllers took their posts at about 2:30 p.m. EST for space shuttle Discovery's STS-133 mission to the International Space Station. The countdown clock began ticking backward from the T-43 hour mark at 3 p.m.

Scheduled to lift off Feb. 24 at 4:50 p.m. EST, Discovery and its six-member crew will deliver the Permanent Multipurpose Module, packed with supplies and critical spare parts, as well as Robonaut 2, the dexterous humanoid astronaut helper, to the orbiting outpost. For more information on the STS-133 mission, visit www.nasa.gov/mission_pages/shuttle/shuttlemissions/sts133/. Photo credit: NASA/Frank Michaux