After moving out of high bay 1 in the Vehicle Assembly Building rolls toward high bay 3.

After moving out of high bay 1 in the Vehicle Assembly Building at NASA's Kennedy Space Center, space shuttle Atlantis' external fuel tank-solid rocket booster stack, atop a mobile launcher platform, rolls toward high bay 3. The move makes room in high bay 1 for the ET-SRB stack for space shuttle Endeavour. Atlantis is targeted for launch on the STS-125 mission on May 12 to service NASA's Hubble Space Telescope. Endeavour will fly on the STS-127 mission to the International Space Station and bring the final segments for Japan's Kibo laboratory. Photo credit: NASA/Dimitri Gerondidakis