Workers monitor the progress of external fuel tank as it is being attached to the twin solid rocket boosters on the mobile launcher platform.

In the Vehicle Assembly Building at NASA's Kennedy Space Center in Florida, workers monitor the progress of external fuel tank, ET-122, for space shuttle Endeavour's STS-134 mission as it is being attached to the twin solid rocket boosters on the mobile launcher platform.

Endeavour and its crew will deliver the Express Logistics Carrier-3 and the Alpha Magnetic Spectrometer to the International Space Station. Launch is targeted for April 19. For more information visit, http://www.nasa.gov/mission_pages/shuttle/shuttlemissions/sts134/index.html. Photo credit: NASA/Jack Pfaller