CAPE CANAVERAL, Fla. -- At NASA Kennedy Space Center's Shuttle Landing Facility in Florida, the STS-134 crew members are greeted by NASA managers and media. From left are Mission Specialist Greg Chamitoff, Commander Mark Kelly, European Space Agency astronaut Roberto Vittori, Mission Specialist Andrew Feustel, Pilot Greg H. Johnson, Mission Specialist Michael Fincke (turned away from camera) and NASA astronaut Scott Kelly. Endeavour and its crew will deliver the Express Logistics Carrier-3, Alpha Magnetic Spectrometer-2 (AMS), a high-pressure gas tank and additional spare parts for the Dextre robotic helper to the station. This will be the final spaceflight for Endeavour. For more information visit, www.nasa.gov/mission_pages/shuttle/shuttlemissions/sts134/index.html. Photo credit: NASA/Kim Shiflett

CAPE CANAVERAL, Fla. -- At the Shuttle Landing Facility at NASA's Kennedy Space Center in Florida, Mission Specialist Andrew Fuestel is photographed after his arrival. The STS-134 crew members landed at 12:52 p.m. EDT to get ready for space shuttle Endeavour's launch to the International Space Station scheduled for Friday, April 29 at 3:47 p.m. Endeavour and its crew will deliver the Express Logistics Carrier-3, Alpha Magnetic Spectrometer-2 (AMS), a high-pressure gas tank and additional spare parts for the Dextre robotic helper to the station. This will be the final spaceflight for Endeavour. For more information visit, www.nasa.gov/mission_pages/shuttle/shuttlemissions/sts134/index.html. Photo credit: NASA/Kim Shiflett

CAPE CANAVERAL, Fla. -- The six STS-134 astronauts pause for a photo after arrival at NASA Kennedy Space Center's Shuttle Landing Facility in Florida, to begin final launch preparations for space shuttle Endeavour's mission to the International Space Station. From left are Mission Specialists Greg Chamitoff, Andrew Feustel, Commander Mark Kelly, Pilot Greg H. Johnson, Mission Specialist Mike Fincke and European Space Agency astronaut Roberto Vittori. Endeavour and its crew will deliver the Express Logistics Carrier-3, Alpha Magnetic Spectrometer-2 (AMS), a high-pressure gas tank and additional spare parts for the Dextre robotic helper to the station. This will be the final spaceflight for Endeavour. For more information visit, www.nasa.gov/mission_pages/shuttle/shuttlemissions/sts134/index.html. Photo credit: NASA/Kim Shiflett

CAPE CANAVERAL, Fla. -- At NASA Kennedy Space Center's Shuttle Landing Facility in Florida, the STS-134 crew members are greeted by Kennedy Center Director Bob Cabana, Shuttle Launch Director Mike Leinbach and other NASA managers after the crew's arrival for final preparations for shuttle Endeavour's liftoff to the International Space Station. From center are Commander Mark Kelly, Bob Cabana, Mike Leinbach, Mission Specialists Greg Chamitoff, European Space Agency astronaut Roberto Vittori, Mission Specialists Andrew Feustel, Michael Fincke and Pilot Greg H. Johnson. Endeavour and its crew will deliver the Express Logistics Carrier-3, Alpha Magnetic Spectrometer-2 (AMS), a high-pressure gas tank and additional spare parts for the Dextre robotic helper to the station. This will be the final spaceflight for Endeavour. For more information visit, www.nasa.gov/mission_pages/shuttle/shuttlemissions/sts134/index.html. Photo credit: NASA/Kim Shiflett

CAPE CANAVERAL, Fla. -- At the Shuttle Landing Facility at NASA's Kennedy Space Center in Florida, European Space Agency astronaut Roberto Vittori is photographed after his arrival. The STS-134 crew members landed at 12:52 p.m. EDT to get ready for space shuttle Endeavour's launch to the International Space Station scheduled for Friday, April 29 at 3:47 p.m. Endeavour and its crew will deliver the Express Logistics Carrier-3, Alpha Magnetic Spectrometer-2 (AMS), a high-pressure gas tank and additional spare parts for the Dextre robotic helper to the station. This will be the final spaceflight for Endeavour. For more information visit, www.nasa.gov/mission_pages/shuttle/shuttlemissions/sts134/index.html. Photo credit: NASA/Kim Shiflett

CAPE CANAVERAL, Fla. -- At NASA Kennedy Space Center's Shuttle Landing Facility in Florida, the STS-134 crew members arrive for final preparations for shuttle Endeavour's liftoff to the International Space Station. On the tarmac are from left (front row) Mission Specialist Michael Fincke and Commander Mark Kelly. Walking behind (from left) are Shuttle Launch Director Mike Leinbach, NASA astronaut Scott Kelly and Deputy Chief of Flight Crew Operations, Brian Kelly. Endeavour and its crew will deliver the Express Logistics Carrier-3, Alpha Magnetic Spectrometer-2 (AMS), a high-pressure gas tank and additional spare parts for the Dextre robotic helper to the station. This will be the final spaceflight for Endeavour. For more information visit, www.nasa.gov/mission_pages/shuttle/shuttlemissions/sts134/index.html. Photo credit: NASA/Kim Shiflett

CAPE CANAVERAL, Fla. -- After arrival at the Shuttle Landing Facility at NASA's Kennedy Space Center in Florida, Commander Mark Kelly speaks to the media. The STS-134 crew members landed at 12:52 p.m. EDT to get ready for space shuttle Endeavour's launch to the International Space Station scheduled for Friday, April 29 at 3:47 p.m. Endeavour and its crew will deliver the Express Logistics Carrier-3, Alpha Magnetic Spectrometer-2 (AMS), a high-pressure gas tank and additional spare parts for the Dextre robotic helper to the station. This will be the final spaceflight for Endeavour. For more information visit, www.nasa.gov/mission_pages/shuttle/shuttlemissions/sts134/index.html. Photo credit: NASA/Kim Shiflett

CAPE CANAVERAL, Fla. -- The crew of space shuttle Endeavour's STS-134 mission arrives at the Shuttle Landing Facility at NASA's Kennedy Space Center aboard T-38 jets to get ready for launch. Seen here is Commander Mark Kelly. The crew arrived at Kennedy 12:52 p.m. EDT to prepare for Endeavour's launch to the International Space Station scheduled for Friday, April 29 at 3:47 p.m. Endeavour and its crew will deliver the Express Logistics Carrier-3, Alpha Magnetic Spectrometer-2 (AMS), a high-pressure gas tank and additional spare parts for the Dextre robotic helper to the station. This will be the final spaceflight for Endeavour. For more information visit, www.nasa.gov/mission_pages/shuttle/shuttlemissions/sts134/index.html. Photo credit: NASA/Kim Shiflett

CAPE CANAVERAL, Fla. -- At the Shuttle Landing Facility at NASA's Kennedy Space Center in Florida, Pilot Greg H. Johnson is photographed after his arrival. The STS-134 crew members landed at 12:52 p.m. EDT to get ready for space shuttle Endeavour's launch to the International Space Station scheduled for Friday, April 29 at 3:47 p.m. Endeavour and its crew will deliver the Express Logistics Carrier-3, Alpha Magnetic Spectrometer-2 (AMS), a high-pressure gas tank and additional spare parts for the Dextre robotic helper to the station. This will be the final spaceflight for Endeavour. For more information visit, www.nasa.gov/mission_pages/shuttle/shuttlemissions/sts134/index.html. Photo credit: NASA/Kim Shiflett

CAPE CANAVERAL, Fla. -- At NASA Kennedy Space Center's Shuttle Landing Facility in Florida, STS-134 Mission Specialist Greg Chamitoff disembarks from his T-38 jet. The STS-134 crew members landed at 12:52 p.m. EDT to get ready for shuttle Endeavour's launch to the International Space Station scheduled for Friday, April 29 at 3:47 p.m. Endeavour and its crew will deliver the Express Logistics Carrier-3, Alpha Magnetic Spectrometer-2 (AMS), a high-pressure gas tank and additional spare parts for the Dextre robotic helper to the station. This will be the final spaceflight for Endeavour. For more information visit, www.nasa.gov/mission_pages/shuttle/shuttlemissions/sts134/index.html. Photo credit: NASA/Kim Shiflett

CAPE CANAVERAL, Fla. -- At NASA Kennedy Space Center's Shuttle Landing Facility in Florida, STS-134 crew members, Pilot Greg H. Johnson and European Space Agency astronaut Roberto Vittori greet each other upon arrival. The STS-134 crew landed at 12:52 p.m. EDT to prepare for shuttle Endeavour's launch to the International Space Station scheduled for Friday April 29 at 3:47 p.m. Endeavour and its crew will deliver the Express Logistics Carrier-3, Alpha Magnetic Spectrometer-2 (AMS), a high-pressure gas tank and additional spare parts for the Dextre robotic helper to the station. This will be the final spaceflight for Endeavour. For more information visit, www.nasa.gov/mission_pages/shuttle/shuttlemissions/sts134/index.html. Photo credit: NASA/Kim Shiflett

CAPE CANAVERAL, Fla. -- At NASA Kennedy Space Center's Shuttle Landing Facility in Florida, European Space Agency astronaut Roberto Vittori climbs out of a T-38 jet. The STS-134 crew members arrived at Kennedy 12:52 p.m. EDT to prepare for shuttle Endeavour's launch to the International Space Station scheduled for Friday, April 29 at 3:47 p.m. Endeavour and its crew will deliver the Express Logistics Carrier-3, Alpha Magnetic Spectrometer-2 (AMS), a high-pressure gas tank and additional spare parts for the Dextre robotic helper to the station. This will be the final spaceflight for Endeavour. For more information visit, www.nasa.gov/mission_pages/shuttle/shuttlemissions/sts134/index.html. Photo credit: NASA/Kim Shiflett

CAPE CANAVERAL, Fla. -- High above NASA's Kennedy Space Center in Florida, space shuttle Endeavour's STS-134 crew members get ready to land their T-38 jets at the Shuttle Landing Facility. The crew arrived at Kennedy 12:52 p.m. EDT to get ready for Endeavour's launch to the International Space Station scheduled for Friday, April 29 at 3:47 p.m. Endeavour and its crew will deliver the Express Logistics Carrier-3, Alpha Magnetic Spectrometer-2 (AMS), a high-pressure gas tank and additional spare parts for the Dextre robotic helper to the station. This will be the final spaceflight for Endeavour. For more information visit, www.nasa.gov/mission_pages/shuttle/shuttlemissions/sts134/index.html. Photo credit: NASA/Kim Shiflett

CAPE CANAVERAL, Fla. -- At the Shuttle Landing Facility at NASA's Kennedy Space Center in Florida, Mission Specialist Michael Fincke is photographed after his arrival. The STS-134 crew members landed at 12:52 p.m. EDT to get ready for space shuttle Endeavour's launch to the International Space Station scheduled for Friday, April 29 at 3:47 p.m. Endeavour and its crew will deliver the Express Logistics Carrier-3, Alpha Magnetic Spectrometer-2 (AMS), a high-pressure gas tank and additional spare parts for the Dextre robotic helper to the station. This will be the final spaceflight for Endeavour. For more information visit, www.nasa.gov/mission_pages/shuttle/shuttlemissions/sts134/index.html. Photo credit: NASA/Kim Shiflett

CAPE CANAVERAL, Fla. -- At NASA Kennedy Space Center's Shuttle Landing Facility in Florida, STS-134 Mission Specialist Andrew Feustel is greeted by Kennedy Center Director Bob Cabana after the crew's arrival for final preparations for shuttle Endeavour's liftoff to the International Space Station. Endeavour and its crew will deliver the Express Logistics Carrier-3, Alpha Magnetic Spectrometer-2 (AMS), a high-pressure gas tank and additional spare parts for the Dextre robotic helper to the station. This will be the final spaceflight for Endeavour. For more information visit, www.nasa.gov/mission_pages/shuttle/shuttlemissions/sts134/index.html. Photo credit: NASA/Kim Shiflett

CAPE CANAVERAL, Fla. -- At NASA Kennedy Space Center's Shuttle Landing Facility in Florida, STS-134 Mission Specialist Andrew Feustel disembarks from his T-38 jet. The STS-134 crew members landed at 12:52 p.m. EDT to get ready for shuttle Endeavour's launch to the International Space Station scheduled for Friday, April 29 at 3:47 p.m. Endeavour and its crew will deliver the Express Logistics Carrier-3, Alpha Magnetic Spectrometer-2 (AMS), a high-pressure gas tank and additional spare parts for the Dextre robotic helper to the station. This will be the final spaceflight for Endeavour. For more information visit, www.nasa.gov/mission_pages/shuttle/shuttlemissions/sts134/index.html. Photo credit: NASA/Kim Shiflett

CAPE CANAVERAL, Fla. -- At the Shuttle Landing Facility at NASA's Kennedy Space Center in Florida, Mission Specialist Greg Chamitoff is photographed after his arrival. The STS-134 crew members landed at 12:52 p.m. EDT to get ready for space shuttle Endeavour's launch to the International Space Station scheduled for Friday, April 29 at 3:47 p.m. Endeavour and its crew will deliver the Express Logistics Carrier-3, Alpha Magnetic Spectrometer-2 (AMS), a high-pressure gas tank and additional spare parts for the Dextre robotic helper to the station. This will be the final spaceflight for Endeavour. For more information visit, www.nasa.gov/mission_pages/shuttle/shuttlemissions/sts134/index.html. Photo credit: NASA/Kim Shiflett

The STS-134 astronauts from left, European Space Agency's Roberto Vittori, Gregory H. Johnson, pilot; Mark Kelly, commander; Michael Fincke, Greg Chamitoff, and Andrew Feustel all mission specialists, pose for a group photograph shortly after landing onboard the space shuttle Endeavour at the Shuttle Landing Facility (SLF) at Kennedy Space Center, Wednesday, June 1, 2011, in Cape Canaveral, Fla. Endeavour, completing a 16-day mission to outfit the International Space Station, spent 299 days in space and traveled more than 122.8 million miles during its 25 flights. It launched on its first mission on May 7, 1992. Photo Credit: (NASA/Bill Ingalls)

CAPE CANAVERAL, Fla. -- In the early morning hours after landing, space shuttle Endeavour's "towback" vehicle slowly pulls it from the Shuttle Landing Facility to Orbiter Processing Facility-1 at NASA's Kennedy Space Center in Florida. A purge unit that pumps conditioned air into a shuttle after landing is connected to Endeavour's aft end. Once inside the processing facility, Endeavour will be prepared for future public display. Endeavour's final return from space completed the 16-day, 6.5-million-mile STS-134 mission. Main gear touchdown was at 2:34:51 a.m. EDT, followed by nose gear touchdown at 2:35:04 a.m., and wheelstop at 2:35:36 a.m. Endeavour and its crew delivered the Alpha Magnetic Spectrometer-2 (AMS) and the Express Logistics Carrier-3 (ELC-3) to the International Space Station. AMS will help researchers understand the origin of the universe and search for evidence of dark matter, strange matter and antimatter from the station. ELC-3 carried spare parts that will sustain station operations once the shuttles are retired from service. STS-134 was the 25th and final flight for Endeavour, which spent 299 days in space, orbited Earth 4,671 times and traveled 122,883,151 miles. Photo credit: NASA/Jack Pfaller

CAPE CANAVERAL, Fla. -- In the early morning hours after landing, space shuttle Endeavour's "towback" vehicle slowly pulls it from the Shuttle Landing Facility to Orbiter Processing Facility-1 at NASA's Kennedy Space Center in Florida. A purge unit that pumps conditioned air into a shuttle after landing is connected to Endeavour's aft end. In the background is the massive Vehicle Assembly Building. Once inside the processing facility, Endeavour will be prepared for future public display. Endeavour's final return from space completed the 16-day, 6.5-million-mile STS-134 mission. Main gear touchdown was at 2:34:51 a.m. EDT, followed by nose gear touchdown at 2:35:04 a.m., and wheelstop at 2:35:36 a.m. Endeavour and its crew delivered the Alpha Magnetic Spectrometer-2 (AMS) and the Express Logistics Carrier-3 (ELC-3) to the International Space Station. AMS will help researchers understand the origin of the universe and search for evidence of dark matter, strange matter and antimatter from the station. ELC-3 carried spare parts that will sustain station operations once the shuttles are retired from service. STS-134 was the 25th and final flight for Endeavour, which spent 299 days in space, orbited Earth 4,671 times and traveled 122,883,151 miles. Photo credit: NASA/Jack Pfaller

CAPE CANAVERAL, Fla. -- In the early morning hours after landing, space shuttle Endeavour's "towback" vehicle slowly pulls it from the Shuttle Landing Facility to Orbiter Processing Facility-1 at NASA's Kennedy Space Center in Florida. A purge unit that pumps conditioned air into a shuttle after landing is connected to Endeavour's aft end. Once inside the processing facility, Endeavour will be prepared for future public display. Endeavour's final return from space completed the 16-day, 6.5-million-mile STS-134 mission. Main gear touchdown was at 2:34:51 a.m. EDT, followed by nose gear touchdown at 2:35:04 a.m., and wheelstop at 2:35:36 a.m. Endeavour and its crew delivered the Alpha Magnetic Spectrometer-2 (AMS) and the Express Logistics Carrier-3 (ELC-3) to the International Space Station. AMS will help researchers understand the origin of the universe and search for evidence of dark matter, strange matter and antimatter from the station. ELC-3 carried spare parts that will sustain station operations once the shuttles are retired from service. STS-134 was the 25th and final flight for Endeavour, which spent 299 days in space, orbited Earth 4,671 times and traveled 122,883,151 miles. Photo credit: NASA/Jack Pfaller

CAPE CANAVERAL, Fla. -- A "towback" vehicle slowly pulls shuttle Endeavour into Orbiter Processing Facility-1 at NASA's Kennedy Space Center in Florida. A purge unit that pumps conditioned air into a shuttle after landing is connected to Endeavour's aft end. Once inside the processing facility, Endeavour will be prepared for future public display. Endeavour's final return from space completed the 16-day, 6.5-million-mile STS-134 mission. Main gear touchdown was at 2:34:51 a.m. EDT, followed by nose gear touchdown at 2:35:04 a.m., and wheelstop at 2:35:36 a.m. Endeavour and its crew delivered the Alpha Magnetic Spectrometer-2 (AMS) and the Express Logistics Carrier-3 (ELC-3) to the International Space Station. AMS will help researchers understand the origin of the universe and search for evidence of dark matter, strange matter and antimatter from the station. ELC-3 carried spare parts that will sustain station operations once the shuttles are retired from service. STS-134 was the 25th and final flight for Endeavour, which spent 299 days in space, orbited Earth 4,671 times and traveled 122,883,151 miles. Photo credit: NASA/Jack Pfaller

CAPE CANAVERAL, Fla. -- Workers accompany shuttle Endeavour as a "towback" vehicle slowly pulls it from the Shuttle Landing Facility to Orbiter Processing Facility-1 at NASA's Kennedy Space Center in Florida. A purge unit that pumps conditioned air into a shuttle after landing is connected to Endeavour's aft end. Once inside the processing facility, Endeavour will be prepared for future public display. Endeavour's final return from space completed the 16-day, 6.5-million-mile STS-134 mission. Main gear touchdown was at 2:34:51 a.m. EDT, followed by nose gear touchdown at 2:35:04 a.m., and wheelstop at 2:35:36 a.m. Endeavour and its crew delivered the Alpha Magnetic Spectrometer-2 (AMS) and the Express Logistics Carrier-3 (ELC-3) to the International Space Station. AMS will help researchers understand the origin of the universe and search for evidence of dark matter, strange matter and antimatter from the station. ELC-3 carried spare parts that will sustain station operations once the shuttles are retired from service. STS-134 was the 25th and final flight for Endeavour, which spent 299 days in space, orbited Earth 4,671 times and traveled 122,883,151 miles. Photo credit: NASA/Jack Pfaller

CAPE CANAVERAL, Fla. -- Workers accompany shuttle Endeavour as a "towback" vehicle slowly pulls it into Orbiter Processing Facility-1 at NASA's Kennedy Space Center in Florida. A purge unit that pumps conditioned air into a shuttle after landing is connected to Endeavour's aft end. Once inside the processing facility, Endeavour will be prepared for future public display. Endeavour's final return from space completed the 16-day, 6.5-million-mile STS-134 mission. Main gear touchdown was at 2:34:51 a.m. EDT, followed by nose gear touchdown at 2:35:04 a.m., and wheelstop at 2:35:36 a.m. Endeavour and its crew delivered the Alpha Magnetic Spectrometer-2 (AMS) and the Express Logistics Carrier-3 (ELC-3) to the International Space Station. AMS will help researchers understand the origin of the universe and search for evidence of dark matter, strange matter and antimatter from the station. ELC-3 carried spare parts that will sustain station operations once the shuttles are retired from service. STS-134 was the 25th and final flight for Endeavour, which spent 299 days in space, orbited Earth 4,671 times and traveled 122,883,151 miles. Photo credit: NASA/Jack Pfaller

CAPE CANAVERAL, Fla. -- A "towback" vehicle slowly pulls shuttle Endeavour from the Shuttle Landing Facility to Orbiter Processing Facility-1 at NASA's Kennedy Space Center in Florida. A purge unit that pumps conditioned air into a shuttle after landing is connected to Endeavour's aft end. Once inside the processing facility, Endeavour will be prepared for future public display. Endeavour's final return from space completed the 16-day, 6.5-million-mile STS-134 mission. Main gear touchdown was at 2:34:51 a.m. EDT, followed by nose gear touchdown at 2:35:04 a.m., and wheelstop at 2:35:36 a.m. Endeavour and its crew delivered the Alpha Magnetic Spectrometer-2 (AMS) and the Express Logistics Carrier-3 (ELC-3) to the International Space Station. AMS will help researchers understand the origin of the universe and search for evidence of dark matter, strange matter and antimatter from the station. ELC-3 carried spare parts that will sustain station operations once the shuttles are retired from service. STS-134 was the 25th and final flight for Endeavour, which spent 299 days in space, orbited Earth 4,671 times and traveled 122,883,151 miles. Photo credit: NASA/Jack Pfaller

CAPE CANAVERAL, Fla. -- In the early morning hours after landing, space shuttle Endeavour's "towback" vehicle slowly pulls it from the Shuttle Landing Facility to Orbiter Processing Facility-1 at NASA's Kennedy Space Center in Florida. A purge unit that pumps conditioned air into a shuttle after landing is connected to Endeavour's aft end. Once inside the processing facility, Endeavour will be prepared for future public display. Endeavour's final return from space completed the 16-day, 6.5-million-mile STS-134 mission. Main gear touchdown was at 2:34:51 a.m. EDT, followed by nose gear touchdown at 2:35:04 a.m., and wheelstop at 2:35:36 a.m. Endeavour and its crew delivered the Alpha Magnetic Spectrometer-2 (AMS) and the Express Logistics Carrier-3 (ELC-3) to the International Space Station. AMS will help researchers understand the origin of the universe and search for evidence of dark matter, strange matter and antimatter from the station. ELC-3 carried spare parts that will sustain station operations once the shuttles are retired from service. STS-134 was the 25th and final flight for Endeavour, which spent 299 days in space, orbited Earth 4,671 times and traveled 122,883,151 miles. Photo credit: NASA/Jack Pfaller

CAPE CANAVERAL, Fla. -- A "towback" vehicle slowly pulls shuttle Endeavour into Orbiter Processing Facility-1 at NASA's Kennedy Space Center in Florida. A purge unit that pumps conditioned air into a shuttle after landing is connected to Endeavour's aft end. Once inside the processing facility, Endeavour will be prepared for future public display. Endeavour's final return from space completed the 16-day, 6.5-million-mile STS-134 mission. Main gear touchdown was at 2:34:51 a.m. EDT, followed by nose gear touchdown at 2:35:04 a.m., and wheelstop at 2:35:36 a.m. Endeavour and its crew delivered the Alpha Magnetic Spectrometer-2 (AMS) and the Express Logistics Carrier-3 (ELC-3) to the International Space Station. AMS will help researchers understand the origin of the universe and search for evidence of dark matter, strange matter and antimatter from the station. ELC-3 carried spare parts that will sustain station operations once the shuttles are retired from service. STS-134 was the 25th and final flight for Endeavour, which spent 299 days in space, orbited Earth 4,671 times and traveled 122,883,151 miles. Photo credit: NASA/Jack Pfaller

CAPE CANAVERAL, Fla. -- In the early morning hours after landing, space shuttle Endeavour's "towback" vehicle slowly pulls it from the Shuttle Landing Facility to Orbiter Processing Facility-1 at NASA's Kennedy Space Center in Florida. A purge unit that pumps conditioned air into a shuttle after landing is connected to Endeavour's aft end. Once inside the processing facility, Endeavour will be prepared for future public display. Endeavour's final return from space completed the 16-day, 6.5-million-mile STS-134 mission. Main gear touchdown was at 2:34:51 a.m. EDT, followed by nose gear touchdown at 2:35:04 a.m., and wheelstop at 2:35:36 a.m. Endeavour and its crew delivered the Alpha Magnetic Spectrometer-2 (AMS) and the Express Logistics Carrier-3 (ELC-3) to the International Space Station. AMS will help researchers understand the origin of the universe and search for evidence of dark matter, strange matter and antimatter from the station. ELC-3 carried spare parts that will sustain station operations once the shuttles are retired from service. STS-134 was the 25th and final flight for Endeavour, which spent 299 days in space, orbited Earth 4,671 times and traveled 122,883,151 miles. Photo credit: NASA/Jack Pfaller

CAPE CANAVERAL, Fla. -- In the early morning hours after landing, space shuttle Endeavour's "towback" vehicle slowly pulls it from the Shuttle Landing Facility to Orbiter Processing Facility-1 at NASA's Kennedy Space Center in Florida. A purge unit that pumps conditioned air into a shuttle after landing is connected to Endeavour's aft end. Once inside the processing facility, Endeavour will be prepared for future public display. Endeavour's final return from space completed the 16-day, 6.5-million-mile STS-134 mission. Main gear touchdown was at 2:34:51 a.m. EDT, followed by nose gear touchdown at 2:35:04 a.m., and wheelstop at 2:35:36 a.m. Endeavour and its crew delivered the Alpha Magnetic Spectrometer-2 (AMS) and the Express Logistics Carrier-3 (ELC-3) to the International Space Station. AMS will help researchers understand the origin of the universe and search for evidence of dark matter, strange matter and antimatter from the station. ELC-3 carried spare parts that will sustain station operations once the shuttles are retired from service. STS-134 was the 25th and final flight for Endeavour, which spent 299 days in space, orbited Earth 4,671 times and traveled 122,883,151 miles. Photo credit: NASA/Jack Pfaller

CAPE CANAVERAL, Fla. -- In the early morning hours after landing, media photograph space shuttle Endeavour as a "towback" vehicle slowly pulls it from the Shuttle Landing Facility to Orbiter Processing Facility-1 at NASA's Kennedy Space Center in Florida. Once inside the processing facility, Endeavour will be prepared for future public display. Endeavour's final return from space completed the 16-day, 6.5-million-mile STS-134 mission. Main gear touchdown was at 2:34:51 a.m. EDT, followed by nose gear touchdown at 2:35:04 a.m., and wheelstop at 2:35:36 a.m. Endeavour and its crew delivered the Alpha Magnetic Spectrometer-2 (AMS) and the Express Logistics Carrier-3 (ELC-3) to the International Space Station. AMS will help researchers understand the origin of the universe and search for evidence of dark matter, strange matter and antimatter from the station. ELC-3 carried spare parts that will sustain station operations once the shuttles are retired from service. STS-134 was the 25th and final flight for Endeavour, which spent 299 days in space, orbited Earth 4,671 times and traveled 122,883,151 miles. Photo credit: NASA/Jack Pfaller

CAPE CANAVERAL, Fla. -- A "towback" vehicle slowly pulls shuttle Endeavour from the Shuttle Landing Facility to Orbiter Processing Facility-1 at NASA's Kennedy Space Center in Florida. A purge unit that pumps conditioned air into a shuttle after landing is connected to Endeavour's aft end. In the background is the massive Vehicle Assembly Building. Once inside the processing facility, Endeavour will be prepared for future public display. Endeavour's final return from space completed the 16-day, 6.5-million-mile STS-134 mission. Main gear touchdown was at 2:34:51 a.m. EDT, followed by nose gear touchdown at 2:35:04 a.m., and wheelstop at 2:35:36 a.m. Endeavour and its crew delivered the Alpha Magnetic Spectrometer-2 (AMS) and the Express Logistics Carrier-3 (ELC-3) to the International Space Station. AMS will help researchers understand the origin of the universe and search for evidence of dark matter, strange matter and antimatter from the station. ELC-3 carried spare parts that will sustain station operations once the shuttles are retired from service. STS-134 was the 25th and final flight for Endeavour, which spent 299 days in space, orbited Earth 4,671 times and traveled 122,883,151 miles. Photo credit: NASA/Jack Pfaller

CAPE CANAVERAL, Fla. -- A "towback" vehicle slowly pulls shuttle Endeavour from the Shuttle Landing Facility to Orbiter Processing Facility-1 at NASA's Kennedy Space Center in Florida. A purge unit that pumps conditioned air into a shuttle after landing is connected to Endeavour's aft end. In the background is the massive Vehicle Assembly Building. Once inside the processing facility, Endeavour will be prepared for future public display. Endeavour's final return from space completed the 16-day, 6.5-million-mile STS-134 mission. Main gear touchdown was at 2:34:51 a.m. EDT, followed by nose gear touchdown at 2:35:04 a.m., and wheelstop at 2:35:36 a.m. Endeavour and its crew delivered the Alpha Magnetic Spectrometer-2 (AMS) and the Express Logistics Carrier-3 (ELC-3) to the International Space Station. AMS will help researchers understand the origin of the universe and search for evidence of dark matter, strange matter and antimatter from the station. ELC-3 carried spare parts that will sustain station operations once the shuttles are retired from service. STS-134 was the 25th and final flight for Endeavour, which spent 299 days in space, orbited Earth 4,671 times and traveled 122,883,151 miles. Photo credit: NASA/Jack Pfaller

CAPE CANAVERAL, Fla. – At C Spray Glass Blasting of Cocoa Beach, Fla., a worker completes the commemorative plaque to mark space shuttle Endeavour’s wheel stop location. The special plaque will be permanently mounted at the Shuttle Landing Facility, or SLF, runway edge at NASA’s Kennedy Space Center in Florida to commemorate Endeavour’s final space shuttle landing. Endeavour completed the STS-134 mission by landing at the SLF on June 1, 2011, at 2:35 a.m. EDT. Endeavour flew 25 missions, completed 4,671 orbits of the Earth, traveled more than 122 million miles and spent 299 days in space. Endeavour carried 173 astronauts to space. Photo credit: NASA/Lorne Mathre

CAPE CANAVERAL, Fla. -- STS-134 Mission Specialists Mike Fincke, left, chats with STS-134 Assistant Launch Director Pete Nickolenko following the successful return of space shuttle Endeavour to NASA's Kennedy Space Center in Florida. Endeavour's final return from space completed the 16-day, 6.5-million-mile STS-134 mission. Main gear touchdown on the Shuttle Landing Facility's Runway 15 was at 2:34:51 a.m. EDT, followed by nose gear touchdown at 2:35:04 a.m., and wheelstop at 2:35:36 a.m. STS-134 delivered the Alpha Magnetic Spectrometer-2 (AMS) and the Express Logistics Carrier-3 (ELC-3) to the International Space Station. AMS will help researchers understand the origin of the universe and search for evidence of dark matter, strange matter and antimatter from the station. ELC-3 carried spare parts that will sustain station operations once the shuttles are retired from service. STS-134 was the 25th and final flight for Endeavour, which spent 299 days in space, orbited Earth 4,671 times and traveled 122,883,151 miles. Photo credit: NASA/Kim Shiflett

CAPE CANAVERAL, Fla. -- STS-134 Commander Mark Kelly addresses media gathered on the Shuttle Landing Facility at NASA's Kennedy Space Center in Florida following the successful landing of space shuttle Endeavour. From left, are the European Space Agency's Roberto Vittori, Pilot Greg H. Johnson, Kelly, and Mission Specialists Mike Fincke, Greg Chamitoff and Drew Feustel. The crew returned to Earth at 2:35 a.m. EDT on Runway 15, completing a 16-day, 6.5-million mile journey to the International Space Station. STS-134 delivered the Alpha Magnetic Spectrometer-2 (AMS) and the Express Logistics Carrier-3 (ELC-3) to the International Space Station. AMS will help researchers understand the origin of the universe and search for evidence of dark matter, strange matter and antimatter from the station. ELC-3 carried spare parts that will sustain station operations once the shuttles are retired from service. STS-134 was the 25th and final flight for Endeavour, which spent 299 days in space, orbited Earth 4,671 times and traveled 122,883,151 miles. Photo credit: NASA/Kim Shiflett

CAPE CANAVERAL, Fla. -- STS-134 Mission Specialists Drew Feustel, left, and Roberto Vittori with the European Space Agency, right, admire space shuttle Endeavour with NASA astronaut Randy Bresnik at NASA's Kennedy Space Center in Florida. Endeavour's final return from space completed the 16-day, 6.5-million-mile STS-134 mission. Main gear touchdown on the Shuttle Landing Facility's Runway 15 was at 2:34:51 a.m. EDT, followed by nose gear touchdown at 2:35:04 a.m., and wheelstop at 2:35:36 a.m. STS-134 delivered the Alpha Magnetic Spectrometer-2 (AMS) and the Express Logistics Carrier-3 (ELC-3) to the International Space Station. AMS will help researchers understand the origin of the universe and search for evidence of dark matter, strange matter and antimatter from the station. ELC-3 carried spare parts that will sustain station operations once the shuttles are retired from service. STS-134 was the 25th and final flight for Endeavour, which spent 299 days in space, orbited Earth 4,671 times and traveled 122,883,151 miles. Photo credit: NASA/Kim Shiflett

CAPE CANAVERAL, Fla. -- STS-134 Mission Specialist Mike Fincke, left, Pilot Greg H. Johnson and Commander Mark Kelly talk with employees following the successful return of space shuttle Endeavour to NASA's Kennedy Space Center in Florida. Endeavour's final return from space completed the 16-day, 6.5-million-mile STS-134 mission. Main gear touchdown on the Shuttle Landing Facility's Runway 15 was at 2:34:51 a.m. EDT, followed by nose gear touchdown at 2:35:04 a.m., and wheelstop at 2:35:36 a.m. STS-134 delivered the Alpha Magnetic Spectrometer-2 (AMS) and the Express Logistics Carrier-3 (ELC-3) to the International Space Station. AMS will help researchers understand the origin of the universe and search for evidence of dark matter, strange matter and antimatter from the station. ELC-3 carried spare parts that will sustain station operations once the shuttles are retired from service. STS-134 was the 25th and final flight for Endeavour, which spent 299 days in space, orbited Earth 4,671 times and traveled 122,883,151 miles. Photo credit: NASA/Kim Shiflett

CAPE CANAVERAL, Fla. -- The landing convoy that will make space shuttle Endeavour safe and secure for towing to its processing hangar begins to pull up around the vehicle following wheelstop on the Shuttle Landing Facility's Runway 15 at NASA's Kennedy Space Center in Florida. Endeavour's final return from space completed the 16-day, 6.5-million-mile STS-134 mission. Main gear touchdown was at 2:34:51 a.m. EDT, followed by nose gear touchdown at 2:35:04 a.m., and wheelstop at 2:35:36 a.m. STS-134 delivered the Alpha Magnetic Spectrometer-2 (AMS) and the Express Logistics Carrier-3 (ELC-3) to the International Space Station. AMS will help researchers understand the origin of the universe and search for evidence of dark matter, strange matter and antimatter from the station. ELC-3 carried spare parts that will sustain station operations once the shuttles are retired from service. STS-134 was the 25th and final flight for Endeavour, which spent 299 days in space, orbited Earth 4,671 times and traveled 122,883,151 miles. Photo credit: NASA/Kim Shiflett

CAPE CANAVERAL, Fla. -- At NASA's Kennedy Space Center in Florida, a team of highly trained personnel inside the Convoy Command Vehicle is ready to "safe" shuttle Endeavour. The command vehicle is equipped to control critical communications between the crew still aboard Endeavour and the Launch Control Center. The team will monitor the health of the orbiter systems and direct convoy operations made up of about 40 vehicles, including 25 specially designed vehicles to assist the crew in leaving the shuttle, and prepare the vehicle for towing from the Shuttle Landing Facility to Orbiter Processing Facility-1. Accompanying the command convoy team are STS-134 assistant launch director Pete Nickolenko and NASA astronaut Janet Kavandi. Endeavour's final return from space completed the 16-day, 6.5-million-mile STS-134 mission. Main gear touchdown was at 2:34:51 a.m. EDT, followed by nose gear touchdown at 2:35:04 a.m., and wheelstop at 2:35:36 a.m. STS-134 delivered the Alpha Magnetic Spectrometer-2 (AMS) and the Express Logistics Carrier-3 (ELC-3) to the International Space Station. AMS will help researchers understand the origin of the universe and search for evidence of dark matter, strange matter and antimatter from the station. ELC-3 carried spare parts that will sustain station operations once the shuttles are retired from service. STS-134 was the 25th and final flight for Endeavour, which spent 299 days in space, orbited Earth 4,671 times and traveled 122,883,151 miles. Photo credit: NASA/Ben Smegelsky

CAPE CANAVERAL, Fla. -- NASA's Deputy Manager for the Space Shuttle Program Leroy Cain, left, and Kennedy Center Director Bob Cabana chat underneath the belly of space shuttle Endeavour following the vehicle's successful trip home. Endeavour's final return from space completed the 16-day, 6.5-million-mile STS-134 mission. Main gear touchdown on the Shuttle Landing Facility's Runway 15 was at 2:34:51 a.m. EDT, followed by nose gear touchdown at 2:35:04 a.m., and wheelstop at 2:35:36 a.m. STS-134 delivered the Alpha Magnetic Spectrometer-2 (AMS) and the Express Logistics Carrier-3 (ELC-3) to the International Space Station. AMS will help researchers understand the origin of the universe and search for evidence of dark matter, strange matter and antimatter from the station. ELC-3 carried spare parts that will sustain station operations once the shuttles are retired from service. STS-134 was the 25th and final flight for Endeavour, which spent 299 days in space, orbited Earth 4,671 times and traveled 122,883,151 miles. Photo credit: NASA/Kim Shiflett

CAPE CANAVERAL, Fla. -- STS-134 Commander Mark Kelly, left, and NASA Administrator Charlie Bolden chat with employees following the successful return of space shuttle Endeavour to NASA's Kennedy Space Center in Florida. Endeavour's final return from space completed the 16-day, 6.5-million-mile STS-134 mission. Main gear touchdown on the Shuttle Landing Facility's Runway 15 was at 2:34:51 a.m. EDT, followed by nose gear touchdown at 2:35:04 a.m., and wheelstop at 2:35:36 a.m. STS-134 delivered the Alpha Magnetic Spectrometer-2 (AMS) and the Express Logistics Carrier-3 (ELC-3) to the International Space Station. AMS will help researchers understand the origin of the universe and search for evidence of dark matter, strange matter and antimatter from the station. ELC-3 carried spare parts that will sustain station operations once the shuttles are retired from service. STS-134 was the 25th and final flight for Endeavour, which spent 299 days in space, orbited Earth 4,671 times and traveled 122,883,151 miles. Photo credit: NASA/Kim Shiflett

CAPE CANAVERAL, Fla. -- At NASA's Kennedy Space Center in Florida, a team of highly trained personnel inside the Convoy Command Vehicle is ready to "safe" shuttle Endeavour. The command vehicle is equipped to control critical communications between the crew still aboard Endeavour and the Launch Control Center. The team will monitor the health of the orbiter systems and direct convoy operations made up of about 40 vehicles, including 25 specially designed vehicles to assist the crew in leaving the shuttle, and prepare the vehicle for towing from the Shuttle Landing Facility to Orbiter Processing Facility-1. Endeavour's final return from space completed the 16-day, 6.5-million-mile STS-134 mission. Main gear touchdown was at 2:34:51 a.m. EDT, followed by nose gear touchdown at 2:35:04 a.m., and wheelstop at 2:35:36 a.m. STS-134 delivered the Alpha Magnetic Spectrometer-2 (AMS) and the Express Logistics Carrier-3 (ELC-3) to the International Space Station. AMS will help researchers understand the origin of the universe and search for evidence of dark matter, strange matter and antimatter from the station. ELC-3 carried spare parts that will sustain station operations once the shuttles are retired from service. STS-134 was the 25th and final flight for Endeavour, which spent 299 days in space, orbited Earth 4,671 times and traveled 122,883,151 miles. Photo credit: NASA/Ben Smegelsky

CAPE CANAVERAL, Fla. -- The landing convoy that will make space shuttle Endeavour safe and secure for towing to its processing hangar begins to pull up around the vehicle following wheelstop on the Shuttle Landing Facility's Runway 15 at NASA's Kennedy Space Center in Florida. Endeavour's final return from space completed the 16-day, 6.5-million-mile STS-134 mission. Main gear touchdown was at 2:34:51 a.m. EDT, followed by nose gear touchdown at 2:35:04 a.m., and wheelstop at 2:35:36 a.m. STS-134 delivered the Alpha Magnetic Spectrometer-2 (AMS) and the Express Logistics Carrier-3 (ELC-3) to the International Space Station. AMS will help researchers understand the origin of the universe and search for evidence of dark matter, strange matter and antimatter from the station. ELC-3 carried spare parts that will sustain station operations once the shuttles are retired from service. STS-134 was the 25th and final flight for Endeavour, which spent 299 days in space, orbited Earth 4,671 times and traveled 122,883,151 miles. Photo credit: NASA/Kim Shiflett

CAPE CANAVERAL, Fla. -- The crew of STS-134 wave to media gathered on the Shuttle Landing Facility at NASA's Kennedy Space Center in Florida following the successful landing of space shuttle Endeavour. From left, are the European Space Agency's Roberto Vittori, Pilot Greg H. Johnson, Commander Mark Kelly, and Mission Specialists Mike Fincke, Greg Chamitoff and Drew Feustel. The crew returned to Earth at 2:35 a.m. EDT on Runway 15, completing a 16-day, 6.5-million mile journey to the International Space Station. STS-134 delivered the Alpha Magnetic Spectrometer-2 (AMS) and the Express Logistics Carrier-3 (ELC-3) to the International Space Station. AMS will help researchers understand the origin of the universe and search for evidence of dark matter, strange matter and antimatter from the station. ELC-3 carried spare parts that will sustain station operations once the shuttles are retired from service. STS-134 was the 25th and final flight for Endeavour, which spent 299 days in space, orbited Earth 4,671 times and traveled 122,883,151 miles. Photo credit: NASA/Kim Shiflett

CAPE CANAVERAL, Fla. -- Managers check out the heat shield tiles that protected space shuttle Endeavour on its successful trip home to the Shuttle Landing Facility's Runway 15 at NASA's Kennedy Space Center in Florida. Endeavour's final return from space completed the 16-day, 6.5-million-mile STS-134 mission. Main gear touchdown was at 2:34:51 a.m. EDT, followed by nose gear touchdown at 2:35:04 a.m., and wheelstop at 2:35:36 a.m. STS-134 delivered the Alpha Magnetic Spectrometer-2 (AMS) and the Express Logistics Carrier-3 (ELC-3) to the International Space Station. AMS will help researchers understand the origin of the universe and search for evidence of dark matter, strange matter and antimatter from the station. ELC-3 carried spare parts that will sustain station operations once the shuttles are retired from service. STS-134 was the 25th and final flight for Endeavour, which spent 299 days in space, orbited Earth 4,671 times and traveled 122,883,151 miles. Photo credit: NASA/Kim Shiflett

CAPE CANAVERAL, Fla. -- Workers measured and marked the spot where shuttle Endeavour's nose gear came to a stop after the vehicle's final return from space completing a 16-day, 6.5-million-mile STS-134 mission. Main gear touchdown was at 2:34:51 a.m. EDT, followed by nose gear touchdown at 2:35:04 a.m., and wheelstop at 2:35:36 a.m. STS-134 delivered the Alpha Magnetic Spectrometer-2 (AMS) and the Express Logistics Carrier-3 (ELC-3) to the International Space Station. AMS will help researchers understand the origin of the universe and search for evidence of dark matter, strange matter and antimatter from the station. ELC-3 carried spare parts that will sustain station operations once the shuttles are retired from service. STS-134 was the 25th and final flight for Endeavour, which spent 299 days in space, orbited Earth 4,671 times and traveled 122,883,151 miles. Photo credit: NASA/Kim Shiflett

CAPE CANAVERAL, Fla. -- Shuttle Launch Director Mike Leinbach, left, greets space shuttle Endeavour's STS-134 crew members following their successful trip home. Endeavour's final return from space completed the 16-day, 6.5-million-mile STS-134 mission. Main gear touchdown on the Shuttle Landing Facility's Runway 15 was at 2:34:51 a.m. EDT, followed by nose gear touchdown at 2:35:04 a.m., and wheelstop at 2:35:36 a.m. STS-134 delivered the Alpha Magnetic Spectrometer-2 (AMS) and the Express Logistics Carrier-3 (ELC-3) to the International Space Station. AMS will help researchers understand the origin of the universe and search for evidence of dark matter, strange matter and antimatter from the station. ELC-3 carried spare parts that will sustain station operations once the shuttles are retired from service. STS-134 was the 25th and final flight for Endeavour, which spent 299 days in space, orbited Earth 4,671 times and traveled 122,883,151 miles. Photo credit: NASA/Kim Shiflett

CAPE CANAVERAL, Fla. -- The Convoy Command Center vehicle is positioned near shuttle Endeavour on the Shuttle Landing Facility at NASA's Kennedy Space Center in Florida. The command vehicle is equipped to control critical communications between the crew still aboard Endeavour and the Launch Control Center. The team will monitor the health of the orbiter systems and direct convoy operations made up of about 40 vehicles, including 25 specially designed vehicles to assist the crew in leaving the shuttle, and prepare the vehicle for towing from the Shuttle Landing Facility to Orbiter Processing Facility-1. Endeavour's final return from space completed the 16-day, 6.5-million-mile STS-134 mission. Main gear touchdown was at 2:34:51 a.m. EDT, followed by nose gear touchdown at 2:35:04 a.m., and wheelstop at 2:35:36 a.m. STS-134 delivered the Alpha Magnetic Spectrometer-2 (AMS) and the Express Logistics Carrier-3 (ELC-3) to the International Space Station. AMS will help researchers understand the origin of the universe and search for evidence of dark matter, strange matter and antimatter from the station. ELC-3 carried spare parts that will sustain station operations once the shuttles are retired from service. STS-134 was the 25th and final flight for Endeavour, which spent 299 days in space, orbited Earth 4,671 times and traveled 122,883,151 miles. Photo credit: NASA/Ben Smegelsky

CAPE CANAVERAL, Fla. -- European Space Agency Director of Human Spaceflight Thomas Reiter, left, Associate Administrator for Space Operations Bill Gerstenmaier, and NASA Kennedy Space Center Director Bob Cabana check out a heat shield tile that protected space shuttle Endeavour on its successful trip home. Endeavour's final return from space completed the 16-day, 6.5-million-mile STS-134 mission. Main gear touchdown on the Shuttle Landing Facility's Runway 15 was at 2:34:51 a.m. EDT, followed by nose gear touchdown at 2:35:04 a.m., and wheelstop at 2:35:36 a.m. STS-134 delivered the Alpha Magnetic Spectrometer-2 (AMS) and the Express Logistics Carrier-3 (ELC-3) to the International Space Station. AMS will help researchers understand the origin of the universe and search for evidence of dark matter, strange matter and antimatter from the station. ELC-3 carried spare parts that will sustain station operations once the shuttles are retired from service. STS-134 was the 25th and final flight for Endeavour, which spent 299 days in space, orbited Earth 4,671 times and traveled 122,883,151 miles. Photo credit: NASA/Kim Shiflett

CAPE CANAVERAL, Fla. -- Associate Administrator for Space Operations Bill Gerstenmaier, left, European Space Agency Director of Human Spaceflight Thomas Reiter and NASA Administrator Charlie Bolden chat underneath the belly of space shuttle Endeavour following the vehicle's successful trip home to NASA's Kennedy Space Center in Florida. Endeavour's final return from space completed the 16-day, 6.5-million-mile STS-134 mission. Main gear touchdown on the Shuttle Landing Facility's Runway 15 was at 2:34:51 a.m. EDT, followed by nose gear touchdown at 2:35:04 a.m., and wheelstop at 2:35:36 a.m. STS-134 delivered the Alpha Magnetic Spectrometer-2 (AMS) and the Express Logistics Carrier-3 (ELC-3) to the International Space Station. AMS will help researchers understand the origin of the universe and search for evidence of dark matter, strange matter and antimatter from the station. ELC-3 carried spare parts that will sustain station operations once the shuttles are retired from service. STS-134 was the 25th and final flight for Endeavour, which spent 299 days in space, orbited Earth 4,671 times and traveled 122,883,151 miles. Photo credit: NASA/Kim Shiflett

CAPE CANAVERAL, Fla. -- STS-134 Pilot Greg H. Johnson, left, and Commander Mark Kelly check out the nose of space shuttle Endeavour following the successful return to NASA's Kennedy Space Center in Florida. Endeavour's final return from space completed the 16-day, 6.5-million-mile STS-134 mission. Main gear touchdown on the Shuttle Landing Facility's Runway 15 was at 2:34:51 a.m. EDT, followed by nose gear touchdown at 2:35:04 a.m., and wheelstop at 2:35:36 a.m. STS-134 delivered the Alpha Magnetic Spectrometer-2 (AMS) and the Express Logistics Carrier-3 (ELC-3) to the International Space Station. AMS will help researchers understand the origin of the universe and search for evidence of dark matter, strange matter and antimatter from the station. ELC-3 carried spare parts that will sustain station operations once the shuttles are retired from service. STS-134 was the 25th and final flight for Endeavour, which spent 299 days in space, orbited Earth 4,671 times and traveled 122,883,151 miles. Photo credit: NASA/Kim Shiflett

CAPE CANAVERAL, Fla. -- The crew members of space shuttle Endeavour's STS-134 mission undergo brief medical checks in the Crew Transport Vehicle before talking to media gathered on the Shuttle Landing Facility at NASA's Kennedy Space Center in Florida. Endeavour's final return from space completed the 16-day, 6.5-million-mile STS-134 mission. Main gear touchdown on the Shuttle Landing Facility's Runway 15 was at 2:34:51 a.m. EDT, followed by nose gear touchdown at 2:35:04 a.m., and wheelstop at 2:35:36 a.m. STS-134 delivered the Alpha Magnetic Spectrometer-2 (AMS) and the Express Logistics Carrier-3 (ELC-3) to the International Space Station. AMS will help researchers understand the origin of the universe and search for evidence of dark matter, strange matter and antimatter from the station. ELC-3 carried spare parts that will sustain station operations once the shuttles are retired from service. STS-134 was the 25th and final flight for Endeavour, which spent 299 days in space, orbited Earth 4,671 times and traveled 122,883,151 miles. Photo credit: NASA/Kim Shiflett

CAPE CANAVERAL, Fla. -- The landing convoy that will make space shuttle Endeavour safe and secure for towing to its processing hangar begins to pull up around the vehicle following wheelstop on the Shuttle Landing Facility's Runway 15 at NASA's Kennedy Space Center in Florida. Endeavour's final return from space completed the 16-day, 6.5-million-mile STS-134 mission. Main gear touchdown was at 2:34:51 a.m. EDT, followed by nose gear touchdown at 2:35:04 a.m., and wheelstop at 2:35:36 a.m. STS-134 delivered the Alpha Magnetic Spectrometer-2 (AMS) and the Express Logistics Carrier-3 (ELC-3) to the International Space Station. AMS will help researchers understand the origin of the universe and search for evidence of dark matter, strange matter and antimatter from the station. ELC-3 carried spare parts that will sustain station operations once the shuttles are retired from service. STS-134 was the 25th and final flight for Endeavour, which spent 299 days in space, orbited Earth 4,671 times and traveled 122,883,151 miles. Photo credit: NASA/Kim Shiflett

CAPE CANAVERAL, Fla. -- NASA Administrator Charlie Bolden, left, and NASA Kennedy Space Center Director Bob Cabana greet space shuttle Endeavour's STS-134 commander and pilot following their successful trip home. Endeavour's final return from space completed the 16-day, 6.5-million-mile STS-134 mission. Main gear touchdown on the Shuttle Landing Facility's Runway 15 was at 2:34:51 a.m. EDT, followed by nose gear touchdown at 2:35:04 a.m., and wheelstop at 2:35:36 a.m. STS-134 delivered the Alpha Magnetic Spectrometer-2 (AMS) and the Express Logistics Carrier-3 (ELC-3) to the International Space Station. AMS will help researchers understand the origin of the universe and search for evidence of dark matter, strange matter and antimatter from the station. ELC-3 carried spare parts that will sustain station operations once the shuttles are retired from service. STS-134 was the 25th and final flight for Endeavour, which spent 299 days in space, orbited Earth 4,671 times and traveled 122,883,151 miles. Photo credit: NASA/Kim Shiflett

CAPE CANAVERAL, Fla. -- The crew of STS-134 pose for a photo on the Shuttle Landing Facility at NASA's Kennedy Space Center in Florida following the successful landing of space shuttle Endeavour. From left, are the European Space Agency's Roberto Vittori, Pilot Greg H. Johnson, Commander Mark Kelly, and Mission Specialists Mike Fincke, Greg Chamitoff and Drew Feustel. The crew returned to Earth at 2:35 a.m. EDT on Runway 15, completing a 16-day, 6.5-million mile journey to the International Space Station. STS-134 delivered the Alpha Magnetic Spectrometer-2 (AMS) and the Express Logistics Carrier-3 (ELC-3) to the International Space Station. AMS will help researchers understand the origin of the universe and search for evidence of dark matter, strange matter and antimatter from the station. ELC-3 carried spare parts that will sustain station operations once the shuttles are retired from service. STS-134 was the 25th and final flight for Endeavour, which spent 299 days in space, orbited Earth 4,671 times and traveled 122,883,151 miles. Photo credit: NASA/Kim Shiflett

CAPE CANAVERAL, Fla. -- STS-134 Commander Mark Kelly addresses media gathered on the Shuttle Landing Facility at NASA's Kennedy Space Center in Florida following the successful landing of space shuttle Endeavour. From left, are the European Space Agency's Roberto Vittori, NASA Administrator Charlie Bolden, Pilot Greg H. Johnson, Kelly, and Mission Specialists Mike Fincke, Greg Chamitoff and Drew Feustel. The crew returned to Earth at 2:35 a.m. EDT on Runway 15, completing a 16-day, 6.5-million mile journey to the International Space Station. STS-134 delivered the Alpha Magnetic Spectrometer-2 (AMS) and the Express Logistics Carrier-3 (ELC-3) to the International Space Station. AMS will help researchers understand the origin of the universe and search for evidence of dark matter, strange matter and antimatter from the station. ELC-3 carried spare parts that will sustain station operations once the shuttles are retired from service. STS-134 was the 25th and final flight for Endeavour, which spent 299 days in space, orbited Earth 4,671 times and traveled 122,883,151 miles. Photo credit: NASA/Kim Shiflett

CAPE CANAVERAL, Fla. -- In the Press Site auditorium at NASA's Kennedy Space Center in Florida, NASA managers brief media after space shuttle Endeavour's successful landing and conclusion of its STS-134 and final mission. From left are, Associate Administrator for Space Operations Bill Gerstenmaier, Space Shuttle Program Launch Integration Manager Mike Moses; and Shuttle Launch Director Mike Leinbach. Endeavour and its crew delivered the Alpha Magnetic Spectrometer-2 (AMS) and the Express Logistics Carrier-3 (ELC-3) to the International Space Station. AMS will help researchers understand the origin of the universe and search for evidence of dark matter, strange matter and antimatter from the station. ELC-3 carried spare parts that will sustain station operations once the shuttles are retired from service. STS-134 was the 25th and final flight for Endeavour, which spent 299 days in space, orbited Earth 4,671 times and traveled 122,883,151 miles. Photo credit: NASA/Kim Shiflett

CAPE CANAVERAL, Fla. -- NASA Administrator Charlie Bolden congratulates the STS-134 crew on a job well done following the successful landing of space shuttle Endeavour at NASA's Kennedy Space Center in Florida. From left, are the European Space Agency's Roberto Vittori, Pilot Greg H. Johnson, Commander Mark Kelly, Bolden, and Mission Specialists Mike Fincke, Greg Chamitoff and Drew Feustel. The crew returned to Earth at 2:35 a.m. EDT on the Shuttle Landing Facility's Runway 15, completing a 16-day, 6.5-million mile journey to the International Space Station. STS-134 delivered the Alpha Magnetic Spectrometer-2 (AMS) and the Express Logistics Carrier-3 (ELC-3) to the International Space Station. AMS will help researchers understand the origin of the universe and search for evidence of dark matter, strange matter and antimatter from the station. ELC-3 carried spare parts that will sustain station operations once the shuttles are retired from service. STS-134 was the 25th and final flight for Endeavour, which spent 299 days in space, orbited Earth 4,671 times and traveled 122,883,151 miles. Photo credit: NASA/Kim Shiflett

CAPE CANAVERAL, Fla. -- STS-134 Commander Mark Kelly addresses media gathered on the Shuttle Landing Facility at NASA's Kennedy Space Center in Florida following the successful landing of space shuttle Endeavour. From left, are the European Space Agency's Roberto Vittori, Pilot Greg H. Johnson, Kelly, and Mission Specialists Mike Fincke, Greg Chamitoff and Drew Feustel. The crew returned to Earth at 2:35 a.m. EDT on Runway 15, completing a 16-day, 6.5-million mile journey to the International Space Station. STS-134 delivered the Alpha Magnetic Spectrometer-2 (AMS) and the Express Logistics Carrier-3 (ELC-3) to the International Space Station. AMS will help researchers understand the origin of the universe and search for evidence of dark matter, strange matter and antimatter from the station. ELC-3 carried spare parts that will sustain station operations once the shuttles are retired from service. STS-134 was the 25th and final flight for Endeavour, which spent 299 days in space, orbited Earth 4,671 times and traveled 122,883,151 miles. Photo credit: NASA/Kim Shiflett

CAPE CANAVERAL, Fla. -- Space shuttle Endeavour's STS-134 crew members talk with employees following their successful trip home. Endeavour's final return from space completed the 16-day, 6.5-million-mile STS-134 mission. Main gear touchdown on the Shuttle Landing Facility's Runway 15 was at 2:34:51 a.m. EDT, followed by nose gear touchdown at 2:35:04 a.m., and wheelstop at 2:35:36 a.m. STS-134 delivered the Alpha Magnetic Spectrometer-2 (AMS) and the Express Logistics Carrier-3 (ELC-3) to the International Space Station. AMS will help researchers understand the origin of the universe and search for evidence of dark matter, strange matter and antimatter from the station. ELC-3 carried spare parts that will sustain station operations once the shuttles are retired from service. STS-134 was the 25th and final flight for Endeavour, which spent 299 days in space, orbited Earth 4,671 times and traveled 122,883,151 miles. Photo credit: NASA/Kim Shiflett

CAPE CANAVERAL, Fla. -- Employees admire space shuttle Endeavour as the landing convoy makes the vehicle safe and secure for towing to its processing hangar at NASA's Kennedy Space Center in Florida. Endeavour's final return from space completed the 16-day, 6.5-million-mile STS-134 mission. Main gear touchdown on the Shuttle Landing Facility's Runway 15 was at 2:34:51 a.m. EDT, followed by nose gear touchdown at 2:35:04 a.m., and wheelstop at 2:35:36 a.m. STS-134 delivered the Alpha Magnetic Spectrometer-2 (AMS) and the Express Logistics Carrier-3 (ELC-3) to the International Space Station. AMS will help researchers understand the origin of the universe and search for evidence of dark matter, strange matter and antimatter from the station. ELC-3 carried spare parts that will sustain station operations once the shuttles are retired from service. STS-134 was the 25th and final flight for Endeavour, which spent 299 days in space, orbited Earth 4,671 times and traveled 122,883,151 miles. Photo credit: NASA/Kim Shiflett

STS-134 crew members, Commander Mark Kelly, Mission Specialists Greg Chamitoff, Andrew Feustel, Pilot Greg H. Johnson, Mission Specialist Mike Fincke and European Space Agency astronaut Roberto Vittori wave following their arrival to Kennedy Space Center, Tuesday, April 26, 2011, in Cape Canaveral, Fla. The six astronauts for space shuttle Endeavour's STS-134 mission to the International Space Station arrived at Kennedy's Shuttle Landing Facility (SLF) in T-38 jets early Tuesday afternoon. Photo Credit: (NASA/Bill Ingalls)

STS-134 Commander Mark Kelly, center, along with his crew speaks to the media following their arrival to Kennedy Space Center, Tuesday, April 26, 2011, in Cape Canaveral, Fla. From left are Mission Specialists Greg Chamitoff, Andrew Feustel, Kelly, Pilot Greg H. Johnson, Mission Specialist Mike Fincke and European Space Agency astronaut Roberto Vittori. The six astronauts for space shuttle Endeavour's STS-134 mission to the International Space Station arrived at Kennedy's Shuttle Landing Facility (SLF) in T-38 jets early Tuesday afternoon. Photo Credit: (NASA/Bill Ingalls)

STS-134 Commander Mark Kelly, center, along with his crew pose for a photograph following their arrival to Kennedy Space Center, Tuesday, April 26, 2011, in Cape Canaveral, Fla. From left are Mission Specialists Greg Chamitoff, Andrew Feustel, Kelly, Pilot Greg H. Johnson, Mission Specialist Mike Fincke and European Space Agency astronaut Roberto Vittori. The six astronauts for space shuttle Endeavour's STS-134 mission to the International Space Station arrived at Kennedy's Shuttle Landing Facility (SLF) in T-38 jets early Tuesday afternoon. Photo Credit: (NASA/Bill Ingalls)

STS-134 Commander Mark Kelly, center, along with his crew speaks to the media following their arrival to Kennedy Space Center, Tuesday, April 26, 2011, in Cape Canaveral, Fla. From left are Mission Specialists Greg Chamitoff, Andrew Feustel, Kelly, Pilot Greg H. Johnson, Mission Specialist Mike Fincke and European Space Agency astronaut Roberto Vittori. The six astronauts for space shuttle Endeavour's STS-134 mission to the International Space Station arrived at Kennedy's Shuttle Landing Facility (SLF) in T-38 jets early Tuesday afternoon. Photo Credit: (NASA/Bill Ingalls)

NASA Administrator Charles Bolden looks at the Space Shuttle Endeavour (STS-134) from the air traffic control tower at the Shuttle Landing Facility (SLF) shortly after Endeavour made its final landing at the Kennedy Space Center, Wednesday, June 1, 2011, in Cape Canaveral, Fla. Endeavour, after completing a 16-day mission to outfit the International Space Station, spent 299 days in space and traveled more than 122.8 million miles during its 25 flights. It launched on its first mission on May 7, 1992. Photo Credit: (NASA/Bill Ingalls)

The STS-134 crew arrives in T-38 jets on Tuesday, April 26, 2011 at the NASA Kennedy Space Center Shuttle Landing Facility (SLF) in Cape Canaveral, Fla. During the 14-day mission, the space shuttle Endeavour and its crew will deliver the Alpha Magnetic Spectrometer (AMS) and spare parts including two S-band communications antennas, a high-pressure gas tank and additional spare parts for Dextre. Launch is targeted for Friday, April 29 at 3:47 p.m. EDT. Photo credit: (NASA/Bill Ingalls)

The STS-134 crew flies over the Shuttle Landing Facility (SLF) in T-38 jets on Tuesday, April 26, 2011 at NASA's Kennedy Space Center in Cape Canaveral, Fla., as they arrive for their upcoming mission. During the 14-day mission, the space shuttle Endeavour and its crew will deliver the Alpha Magnetic Spectrometer (AMS) and spare parts including two S-band communications antennas, a high-pressure gas tank and additional spare parts for Dextre. Launch is targeted for Friday, April 29 at 3:47 p.m. EDT. Photo credit: (NASA/Bill Ingalls)

NASA Shuttle Landing Facility (SLF) ground crew prepare for the arrival of the STS-134 crew in T-38 jets on Tuesday, April 26, 2011 at NASA's Kennedy Space Center in Cape Canaveral, Fla. During the 14-day mission, the space shuttle Endeavour and its crew will deliver the Alpha Magnetic Spectrometer (AMS) and spare parts including two S-band communications antennas, a high-pressure gas tank and additional spare parts for Dextre. Launch is targeted for Friday, April 29 at 3:47 p.m. EDT. Photo credit: (NASA/Bill Ingalls)

The STS-134 crew arrives in T-38 jets on Tuesday, April 26, 2011 at the NASA Kennedy Space Center Shuttle Landing Facility (SLF) in Cape Canaveral, Fla. During the 14-day mission, the space shuttle Endeavour and its crew will deliver the Alpha Magnetic Spectrometer (AMS) and spare parts including two S-band communications antennas, a high-pressure gas tank and additional spare parts for Dextre. Launch is targeted for Friday, April 29 at 3:47 p.m. EDT. Photo credit: (NASA/Bill Ingalls)