NASA Administrator Charlie Bolden monitors the countdown to liftoff of space shuttle Endeavour in Firing Room 4 of the Launch Control Center.

NASA Administrator Charlie Bolden, right, monitors the countdown to liftoff of space shuttle Endeavour in Firing Room 4 of the Launch Control Center at NASA's Kennedy Space Center in Florida. Endeavour lifted off on its STS-134 mission to the International Space Station on time at 8:56 a.m. EDT on May 16.

The shuttle and its six-member crew are embarking on a mission to deliver the Alpha Magnetic Spectrometer-2 (AMS), Express Logistics Carrier-3, a high-pressure gas tank and additional spare parts for the Dextre robotic helper to the space station. Endeavour's first launch attempt on April 29 was scrubbed because of an issue associated with a faulty power distribution box called the aft load control assembly-2 (ALCA-2). For more information visit, www.nasa.gov/mission_pages/shuttle/shuttlemissions/sts134/index.html. Photo credit: NASA/Kim Shiflett