Workers track as it is lowered into high bay 3 between the solid rocket boosters waiting on the mobile launcher platform.

In the Vehicle Assembly Building at NASA's Kennedy Space Center, workers track the movement of space shuttle Discovery's external tank as it is lowered into high bay 3 between the solid rocket boosters waiting on the mobile launcher platform. The tank and rockets will be mated for the launch of Discovery on the STS-124 mission to the International Space Station, targeted for May 31. On the mission, Discovery will transport the Kibo Japanese Experiment Module - Pressurized Module (JEM-PM) and the Japanese Remote Manipulator System (JEM-RMS) to the space station to add to the Kibo laboratory. Photo credit: NASA/Kim Shiflett