CAPE CANAVERAL, Fla. -- STS-134 Mission Specialists Greg Chamitoff, standing, and Andrew Feustel perform a walkdown of space shuttle Endeavour's payload bay. The Express Logistics Carrier-3 packed with spare parts and the Alpha Magnetic Spectrometer-2 (AMS) are inside the bay for the STS-134 mission to the International Space Station. Chamitoff, Feustel and fellow Mission Specialist Michael Fincke are the designated spacewalkers for the mission. Endeavour's six crew members are at Kennedy for the launch countdown dress rehearsal called the Terminal Countdown Demonstration Test (TCDT) and related training. Endeavour is targeted to launch April 19 at 7:48 p.m. EDT on its final spaceflight mission. For more information visit, www.nasa.gov/mission_pages/shuttle/shuttlemissions/sts134/index.html. Photo credit: NASA/Kim Shiflett

CAPE CANAVERAL, Fla. -- STS-134 Commander Mark Kelly, lying down, and Professor Sam Ting, Alpha Magnetic Spectrometer-2 (AMS) principal investigator at the Massachusetts Institute of Technology, perform a walkdown of space shuttle Endeavour's payload bay. The Express Logistics Carrier-3 packed with spare parts and the (AMS) are inside the bay for the STS-134 mission to the International Space Station. Endeavour's six crew members are at Kennedy for the launch countdown dress rehearsal called the Terminal Countdown Demonstration Test (TCDT) and related training. Endeavour is targeted to launch April 19 at 7:48 p.m. EDT on its final spaceflight mission. For more information visit, www.nasa.gov/mission_pages/shuttle/shuttlemissions/sts134/index.html. Photo credit: NASA/Kim Shiflett

CAPE CANAVERAL, Fla. -- STS-134 Mission Specialist Andrew Feustel performs a walkdown of space shuttle Endeavour's payload bay. The Express Logistics Carrier-3 packed with spare parts and the Alpha Magnetic Spectrometer-2 (AMS) are inside the bay for the STS-134 mission to the International Space Station. Feustel and fellow Mission Specialists Greg Chamitoff and Michael Fincke are the designated spacewalkers for the mission. Endeavour's six crew members are at Kennedy for the launch countdown dress rehearsal called the Terminal Countdown Demonstration Test (TCDT) and related training. Endeavour is targeted to launch April 19 at 7:48 p.m. EDT on its final spaceflight mission. For more information visit, www.nasa.gov/mission_pages/shuttle/shuttlemissions/sts134/index.html. Photo credit: NASA/Kim Shiflett

CAPE CANAVERAL, Fla. -- STS-134 Pilot Greg H. Johnson performs a walkdown of space shuttle Endeavour's payload bay. The Express Logistics Carrier-3 packed with spare parts and the Alpha Magnetic Spectrometer-2 (AMS) are inside the bay for the STS-134 mission to the International Space Station. Endeavour's six crew members are at Kennedy for the launch countdown dress rehearsal called the Terminal Countdown Demonstration Test (TCDT) and related training. Endeavour is targeted to launch April 19 at 7:48 p.m. EDT on its final spaceflight mission. For more information visit, www.nasa.gov/mission_pages/shuttle/shuttlemissions/sts134/index.html. Photo credit: NASA/Kim Shiflett

CAPE CANAVERAL, Fla. -- STS-134 Mission Specialist Andrew Feustel performs a walkdown of space shuttle Endeavour's payload bay. The Express Logistics Carrier-3 packed with spare parts and the Alpha Magnetic Spectrometer-2 (AMS) are inside the bay for the STS-134 mission to the International Space Station. Feustel and fellow Mission Specialists Greg Chamitoff and Michael Fincke are the designated spacewalkers for the mission. Endeavour's six crew members are at Kennedy for the launch countdown dress rehearsal called the Terminal Countdown Demonstration Test (TCDT) and related training. Endeavour is targeted to launch April 19 at 7:48 p.m. EDT on its final spaceflight mission. For more information visit, www.nasa.gov/mission_pages/shuttle/shuttlemissions/sts134/index.html. Photo credit: NASA/Kim Shiflett

CAPE CANAVERAL, Fla. -- STS-134 Mission Specialist Michael Fincke, right, and Pilot Greg H. Johnson, center, perform a walkdown of space shuttle Endeavour's payload bay with shuttle technicians. The Express Logistics Carrier-3 packed with spare parts and the Alpha Magnetic Spectrometer-2 (AMS) are inside the bay for the STS-134 mission to the International Space Station. Endeavour's six crew members are at Kennedy for the launch countdown dress rehearsal called the Terminal Countdown Demonstration Test (TCDT) and related training. Endeavour is targeted to launch April 19 at 7:48 p.m. EDT on its final spaceflight mission. For more information visit, www.nasa.gov/mission_pages/shuttle/shuttlemissions/sts134/index.html. Photo credit: NASA/Kim Shiflett

CAPE CANAVERAL, Fla. -- STS-134 Mission Specialist Michael Fincke, right, performs a walkdown of space shuttle Endeavour's payload bay with a shuttle technician. The Express Logistics Carrier-3 packed with spare parts and the Alpha Magnetic Spectrometer-2 (AMS) are inside the bay for the STS-134 mission to the International Space Station. Fincke and fellow Mission Specialists Greg Chamitoff and Andrew Feustel are the designated spacewalkers for the mission. Endeavour's six crew members are at Kennedy for the launch countdown dress rehearsal called the Terminal Countdown Demonstration Test (TCDT) and related training. Endeavour is targeted to launch April 19 at 7:48 p.m. EDT on its final spaceflight mission. For more information visit, www.nasa.gov/mission_pages/shuttle/shuttlemissions/sts134/index.html. Photo credit: NASA/Kim Shiflett

CAPE CANAVERAL, Fla. -- STS-134 Mission Specialist Greg Chamitoff performs a walkdown of space shuttle Endeavour's payload bay. The Express Logistics Carrier-3 packed with spare parts and the Alpha Magnetic Spectrometer-2 (AMS) are inside the bay for the STS-134 mission to the International Space Station. Chamitoff and fellow Mission Specialists Andrew Feustel and Michael Fincke are the designated spacewalkers for the mission. Endeavour's six crew members are at Kennedy for the launch countdown dress rehearsal called the Terminal Countdown Demonstration Test (TCDT) and related training. Endeavour is targeted to launch April 19 at 7:48 p.m. EDT on its final spaceflight mission. For more information visit, www.nasa.gov/mission_pages/shuttle/shuttlemissions/sts134/index.html. Photo credit: NASA/Kim Shiflett