Work platforms inside the Vehicle Assembly Building begin to surround Discovery its rocket boosters and external fuel tank.

Work platforms inside the Vehicle Assembly Building at NASA's Kennedy Space Center in Florida begin to surround space shuttle Discovery, its solid rocket boosters and external fuel tank. The shuttle rolled back from Launch Pad 39A so technicians can examine the external tank and re-apply foam where 89 sensors were installed on the tank's aluminum skin for an instrumented tanking test on Dec. 17. The sensors were used to measure changes in the tank as super-cold propellants were pumped in and drained out. Data and analysis from the test will be used to determine what caused the tops of two, 21-foot-long support beams, called stringers, on the outside of the intertank to crack during fueling on Nov. 5.

Discovery's next launch opportunity to the International Space Station on the STS-133 mission is no earlier than Feb. 3, 2011. For more information on STS-133, visit www.nasa.gov/mission_pages/shuttle/shuttlemissions/sts133/. Photo credit: NASA/Frank Michaux