JSC2011-E-028487 (24 March 2011) --- News media representatives are pictured during an STS-134 preflight press conference at NASA's Johnson Space Center. Photo credit: NASA or National Aeronautics and Space Administration

JSC2011-E-028496 (24 March 2011) --- NASA astronaut Andrew Feustel, STS-134 mission specialist, responds to a question from a reporter during a preflight press conference at NASA's Johnson Space Center. Photo credit: NASA or National Aeronautics and Space Administration

JSC2011-E-028490 (24 March 2011) --- NASA astronaut Michael Fincke, STS-134 mission specialist, responds to a question from a reporter during a preflight press conference at NASA's Johnson Space Center. Photo credit: NASA or National Aeronautics and Space Administration

JSC2011-E-028493 (24 March 2011) --- NASA astronaut Mark Kelly, STS-134 commander, responds to a question from a reporter during a preflight press conference at NASA's Johnson Space Center. Photo credit: NASA or National Aeronautics and Space Administration

JSC2011-E-028488 (24 March 2011) --- NASA astronaut Greg H. Johnson, STS-134 pilot, responds to a question from a reporter during a preflight press conference at NASA's Johnson Space Center. Photo credit: NASA or National Aeronautics and Space Administration

JSC2011-E-028491 (24 March 2011) --- European Space Agency astronaut Roberto Vittori, STS-134 mission specialist, fields a question from a reporter during a preflight press conference at NASA's Johnson Space Center. Photo credit: NASA or National Aeronautics and Space Administration

JSC2011-E-028498 (24 March 2011) --- European Space Agency astronaut Roberto Vittori, STS-134 mission specialist, responds to a question from a reporter during a preflight press conference at NASA's Johnson Space Center. Photo credit: NASA or National Aeronautics and Space Administration

JSC2011-E-028492 (24 March 2011) --- NASA astronaut Greg Chamitoff, STS-134 mission specialist, fields a question from a reporter during a preflight press conference at NASA's Johnson Space Center. Photo credit: NASA or National Aeronautics and Space Administration

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)

Barbie Dolls stand by during the STS-134 Tweetup, Thursday, April 28, 2011, at Kennedy Space Center in Cape Canaveral, Fla. About 150 NASA Twitter followers attended the event. Photo Credit: (NASA/Paul E. Alers)

Actor and Producer Levar Burton tweets with two devices during the STS-134 Tweetup, Thursday, April 28, 2011, at Kennedy Space Center in Cape Canaveral, Fla. About 150 NASA Twitter followers attended the event. Photo Credit: (NASA/Paul E. Alers)

Actor Seth Green, a NASA Twitter follower, holds up his mobile device bearing the NASA emblem during the STS-134 Tweetup, Thursday, April 28, 2011, at Kennedy Space Center in Cape Canaveral, Fla. About 150 NASA Twitter followers attended the event. Photo Credit: (NASA/Paul E. Alers)

NASA Astronaut Clay Anderson speaks to NASA Twitter followers during the STS-134 Tweetup, Thursday, April 28, 2011, at Kennedy Space Center in Cape Canaveral, Fla. About 150 NASA Twitter followers attended the event. Photo Credit: (NASA/Paul E. Alers)

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)

NASA Twitter followers, who particiapted in the STS-134 Tweetup are seen together by the launch clock, Friday, April 29, 2011, at Kennedy Space Center in Cape Canaveral, Fla. About 150 NASA Twitter followers attended the event. Later the group will watch the launch of Endeavour as it heads to the International Space Station on a 14-day mission to 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. Liftoff is targeted for 3:47 pm. Photo Credit: (NASA/Paul E. Alers)

Actor Seth Green, a NASA Twitter follower, tweets from his device during the STS-134 Tweetup, Thursday, April 28, 2011, at Kennedy Space Center in Cape Canaveral, Fla. About 150 NASA Twitter followers attended the event. Photo Credit: (NASA/Paul E. Alers)

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)

Heather Good, Twitter handle @foundonmars, tweets during the STS-134 Tweetup, Thursday, April 28, 2011, at Kennedy Space Center in Cape Canaveral, Fla. About 150 NASA Twitter followers attended the event. Photo Credit: (NASA/Paul E. Alers)

NASA Twitter followers are seen through a space suit helmet during the STS-134 Tweetup, Thursday, April 28, 2011, at Kennedy Space Center in Cape Canaveral, Fla. About 150 NASA Twitter followers attended the event. Photo Credit: (NASA/Paul E. Alers)

Water pours out of the 290-foot-high tower that holds 300,000 gallons of water used for sound suppression during shuttle launches on launch pad 39a shortly after the rollback of the Rotating Service Structure (RSS) from the space shuttle Endeavour, Thursday, April 28, 2011, at Kennedy Space Center in Cape Canaveral, Fla. During the 14-day mission, Endeavour and the STS-134 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)

JSC2011-E-028489 (24 March 2011) --- The STS-134 crew members along with Public Affairs Office moderator Nicole Cloutier (left) are pictured during a preflight press conference at NASA's Johnson Space Center. From the second left are NASA astronauts Mark Kelly, commander; Greg H. Johnson, pilot; and Michael Fincke, European Space Agency?s Roberto Vittori, and NASA astronauts Andrew Feustel and Greg Chamitoff, all mission specialists. News media representatives are visible in the foreground. Photo credit: NASA or National Aeronautics and Space Administration

JSC2011-E-028501 (24 March 2011) --- The STS-134 crew members along with Public Affairs Office moderator Nicole Cloutier (left) are pictured during a preflight press conference at NASA's Johnson Space Center. From the second left are NASA astronauts Mark Kelly, commander; Greg H. Johnson, pilot; and Michael Fincke, European Space Agency?s Roberto Vittori, and NASA astronauts Andrew Feustel and Greg Chamitoff, all mission specialists. News media representatives are visible in the foreground. Photo credit: NASA or National Aeronautics and Space Administration

The space shuttle Endeavour is seen on launch pad 39a after the rollback of the Rotating Service Structure (RSS), Thursday, April 28, 2011, at Kennedy Space Center in Cape Canaveral, Fla. During the 14-day mission, Endeavour and the STS-134 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 space shuttle Endeavour is seen on launch pad 39a after the rollback of the Rotating Service Structure (RSS), Thursday, April 28, 2011, at Kennedy Space Center in Cape Canaveral, Fla. During the 14-day mission, Endeavour and the STS-134 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 space shuttle Endeavour is seen on launch pad 39a as a storm passes by prior to the rollback of the Rotating Service Structure (RSS), Thursday, April 28, 2011, at Kennedy Space Center in Cape Canaveral, Fla. During the 14-day mission, Endeavour and the STS-134 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 space shuttle Endeavour is seen on launch pad 39a as a storm passes by prior to the rollback of the Rotating Service Structure (RSS), Thursday, April 28, 2011, at Kennedy Space Center in Cape Canaveral, Fla. During the 14-day mission, Endeavour and the STS-134 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)

201105150010hq (15 May 2011) --- The space shuttle Endeavour is seen on launch pad 39A after the rollback of the Rotating Service Structure (RSS), May 15, 2011, at Kennedy Space Center in Cape Canaveral, Fla. During the mission, Endeavour and the STS-134 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 May 16 at 8:56 a.m. (EDT). Photo credit: NASA/Bill Ingalls

The space shuttle Endeavour is seen on launch pad 39a after the rollback of the Rotating Service Structure (RSS), Thursday, April 28, 2011, at Kennedy Space Center in Cape Canaveral, Fla. During the 14-day mission, Endeavour and the STS-134 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 space shuttle Endeavour is seen on launch pad 39a after the rollback of the Rotating Service Structure (RSS), Thursday, April 28, 2011, at Kennedy Space Center in Cape Canaveral, Fla. During the 14-day mission, Endeavour and the STS-134 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)

An faint profile outline of the space shuttle Endeavour is seen projected in the sky as powerful xenon lights illuminate launch pad 39a shortly after the rollback of the Rotating Service Structure (RSS) from Endeavour, Thursday, April 28, 2011, at Kennedy Space Center in Cape Canaveral, Fla. During the 14-day mission, Endeavour and the STS-134 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 space shuttle Endeavour is seen reflected in a puddle of water on launch pad 39a after the rollback of the Rotating Service Structure (RSS), Thursday, April 28, 2011, at Kennedy Space Center in Cape Canaveral, Fla. During the 14-day mission, Endeavour and the STS-134 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)

201105150002hq (15 May 2011) --- The space shuttle Endeavour is seen on launch pad 39A after the rollback of the Rotating Service Structure (RSS), May 15, 2011, at Kennedy Space Center in Cape Canaveral, Fla. During the mission, Endeavour and the STS-134 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 May 16 at 8:56 a.m. (EDT). Photo credit: NASA/Bill Ingalls

The space shuttle Endeavour is seen on launch pad 39a as a storm passes by prior to the rollback of the Rotating Service Structure (RSS), Thursday, April 28, 2011, at Kennedy Space Center in Cape Canaveral, Fla. During the 14-day mission, Endeavour and the STS-134 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 space shuttle Endeavour is seen on launch pad 39a after the rollback of the Rotating Service Structure (RSS), Thursday, April 28, 2011, at Kennedy Space Center in Cape Canaveral, Fla. During the 14-day mission, Endeavour and the STS-134 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)

Heather Paul, a project engineer for Johnson Space Center, talks about space suit technology during the STS-134 Tweetup, Thursday, April 28, 2011, at Kennedy Space Center in Cape Canaveral, Fla. About 150 NASA Twitter followers attended the event. Photo Credit: (NASA/Paul E. Alers)

The space shuttle Endeavour is seen on launch pad 39a after the rollback of the Rotating Service Structure (RSS), Thursday, April 28, 2011, at Kennedy Space Center in Cape Canaveral, Fla. During the 14-day mission, Endeavour and the STS-134 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 space shuttle Endeavour is seen on launch pad 39a after the rollback of the Rotating Service Structure (RSS), Thursday, April 28, 2011, at Kennedy Space Center in Cape Canaveral, Fla. During the 14-day mission, Endeavour and the STS-134 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)

Actor Seth Green, right, takes a quick photo of two NASA Tweeps holding a Golden Orb Spider during the STS-134 Tweetup, Thursday, April 28, 2011, at Kennedy Space Center in Cape Canaveral, Fla. About 150 NASA Twitter followers attended the event. Photo Credit: (NASA/Paul E. Alers)

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)

President Barack Obama, First Lady Michelle Obama, daughters Malia, left, Sasha, and Astronaut Janet Kavandi walk under the landing gear from beneath the nose of space shuttle Atlantis as they visit Kennedy Space Center in Cape Canaveral, Fla., Friday, April 29, 2011. Photo Credit: (NASA/Bill Ingalls)

Terry White, United Space Alliance project lead for thermal protection systems, left, sakes hands with President Barack Obama after showing his family, Sasha, First Lady Michelle Obama, Malia, and Marian Robinson, how tiles work on the space shuttle during their visit to the Orbital Processing Facility at the NASA Kennedy Space Center in Cape Canaveral, Fla., Friday, April 29, 2011. Photo Credit: (NASA/Bill Ingalls)

NASA Twitter followers from left; Leigh Checkman (@liprap), Barbara Nixon (@BarbaraNixon), and Beth Schaefer (@boonbeth), hold up signs just before the Astrovan, carrying the STS-134 crew out to launch pad 39a passed by, early Monday, May 16, 2011, at Kennedy Space Center in Cape Canaveral, Fla. During the 16-day mission, Endeavour, with Commander Mark Kelly, Pilot Gregory H. Johnson, Mission Specialists Michael Fincke, Greg Chamitoff, Andrew Feustel and European Space Agency astronaut Robert Vittori 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. Photo Credit: (NASA/Paul E. Alers)

President Barack Obama, daughters Malia, left, Sasha, and Astronaut Janet Kavandi walk under the landing gear from beneath the nose of space shuttle Atlantis as they visit Kennedy Space Center in Cape Canaveral, Fla., Friday, April 29, 2011. Photo Credit: (NASA/Bill Ingalls)

President Barack Obama holds hands with his daughter Malia as they walk under the space shuttle Atlantis during a tour the first family received of the the NASA Orbital Processing Facility given by Director of Flight Crew Operations for the Johnson Space Center and Astronaut, Janet Kavandi, right, at the NASA Kennedy Space Center in Cape Canaveral, Fla., Friday, April 29, 2011. 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)

President Barack Obama, First Lady Michelle Obama, daughters Malia, left, Sasha, and Astronaut Janet Kavandi walk under the landing gear from beneath the nose of space shuttle Atlantis as they visit Kennedy Space Center in Cape Canaveral, Fla., Friday, April 29, 2011. Photo Credit: (NASA/Bill Ingalls)

Terry White, United Space Alliance project lead for thermal protection systems, left, shows President Barack Obama and his family, from left, First Lady Michelle Obama, Malia, Marian Robinson and Sasha, how tiles work on the space shuttle during their visit to the Orbital Processing Facility at the NASA Kennedy Space Center in Cape Canaveral, Fla., Friday, April 29, 2011. Looking on is Director of Flight Crew Operations for the Johnson Space Center and Astronaut, Janet Kavandi. Photo Credit: (NASA/Bill Ingalls)

Terry White, United Space Alliance project lead for thermal protection systems, left, shows President Barack Obama and his family, from left, First Lady Michelle Obama, Malia, Marian Robinson and Sasha, how tiles work on the space shuttle during their visit to the Orbital Processing Facility at the NASA Kennedy Space Center in Cape Canaveral, Fla., Friday, April 29, 2011. Photo Credit: (NASA/Bill Ingalls)

Terry White, United Space Alliance project lead for thermal protection systems, left, shows President Barack Obama and his family, from left, First Lady Michelle Obama, Malia, Marian Robinson and Sasha, how tiles work on the space shuttle during their visit to the Orbital Processing Facility at the NASA Kennedy Space Center in Cape Canaveral, Fla., Friday, April 29, 2011. Photo Credit: (NASA/Bill Ingalls)

President Barack Obama, First Lady Michelle Obama, daughters Malia, Sasha, and the First Lady's mother Marian Robinson, are shown the space shuttle Atlantis during a tour of the Orbital Processing Facility by NASA Astronaut Janet Kavandi during their visit to the Kennedy Space Center in Cape Canaveral, Fla., Friday, April 29, 2011. Photo Credit: (NASA/Bill Ingalls)

President Barack Obama, First Lady Michelle Obama, daughters Malia, left, Sasha, Marian Robinson, Astronaut Janet Kavandi and United Space Alliance project lead for thermal protection systems Terry White, walk under the landing gear of the space shuttle Atlantis as they visit Kennedy Space Center in Cape Canaveral, Fla., Friday, April 29, 2011. Photo Credit: (NASA/Bill Ingalls)

President Barack Obama and First Lady Michelle Obama meet with STS-134 space shuttle Endeavor commander Mark Kelly, right, and shuttle astronauts, from left, Andrew Feustel, European Space Agency’s Roberto Vittori, Michael Fincke, Gregory H. Johnson, and Greg Chamitoff, after their launch was scrubbed, Friday, April 29, 2011, at Kennedy Space Center in Cape Canaveral, Fla. Photo Credit: (NASA/Bill Ingalls)

President Barack Obama holds hands with his daughter Malia as they walk under the space shuttle Atlantis with First Lady Michelle Obama, Sasha, and Marian Robinson during a tour they received of the NASA Orbital Processing Facility given by Astronaut, Janet Kavandi, and United Space Alliance project lead for thermal protection systems Terry White, right, at the NASA Kennedy Space Center in Cape Canaveral, Fla., Friday, April 29, 2011. Photo Credit: (NASA/Bill Ingalls)

President Barack Obama and First Lady Michelle Obama meet with STS-134 space shuttle Endeavor commander Mark Kelly, right, and shuttle astronauts, from left, Andrew Feustel, European Space Agency’s Roberto Vittori, Michael Fincke, Gregory H. Johnson, and Greg Chamitoff, after their launch was scrubbed, Friday, April 29, 2011, at Kennedy Space Center in Cape Canaveral, Fla. Photo Credit: (NASA/Bill Ingalls)