CAPE CANAVERAL, Fla. – In Orbiter Processing Facility bay 2 at NASA's Kennedy Space Center in Florida, a worker inside space shuttle Endeavour checks the area where the new window will be installed. Endeavour is the designated launch vehicle for the STS-127 mission. The Japanese Experiment Module's Experiment Logistics Module-Exposed Section, or ELM-ES, is part of the payload on the mission, targeted for launch on May 15. Photo credit: NASA/Tim Jacobs

CAPE CANAVERAL, Fla. –– Space shuttle Atlantis on Launch Pad 39A is viewed across the lagoon at NASA's Kennedy Space Center in Florida. Atlantis is targeted to launch May 12 on the STS-125 mission to upgrade NASA's Hubble Space Telescope. Endeavour will be prepared on the pad for liftoff in the unlikely event that a rescue mission is necessary following space shuttle Atlantis' launch May 12 on the STS-125 mission to upgrade NASA's Hubble Space Telescope. After Atlantis is cleared to land, Endeavour will move to Launch Pad 39A for its upcoming STS-127 mission to the International Space Station, targeted to launch June 13. Photo credit: NASA/Jack Pfaller

CAPE CANAVERAL, Fla. –– Sunlight spotlights space shuttle Endeavour poised on Launch Pad 39B at NASA's Kennedy Space Center in Florida. In the foreground is the railway that services Kennedy. Surrounding the pad are the lightning towers erected for NASA's Constellation Program, which will use the pad for Ares rocket launches. Endeavour will be prepared on the pad for liftoff in the unlikely event that a rescue mission is necessary following space shuttle Atlantis' launch May 12 on the STS-125 mission to upgrade NASA's Hubble Space Telescope. After Atlantis is cleared to land, Endeavour will move to Launch Pad 39A for its upcoming STS-127 mission to the International Space Station, targeted to launch June 13. Photo credit: NASA/Jack Pfaller

CAPE CANAVERAL, Fla. –– Space shuttle Atlantis on Launch Pad 39A is viewed across the lagoon at NASA's Kennedy Space Center in Florida. Atlantis is targeted to launch May 12 on the STS-125 mission to upgrade NASA's Hubble Space Telescope. Endeavour will be prepared on the pad for liftoff in the unlikely event that a rescue mission is necessary following space shuttle Atlantis' launch May 12 on the STS-125 mission to upgrade NASA's Hubble Space Telescope. After Atlantis is cleared to land, Endeavour will move to Launch Pad 39A for its upcoming STS-127 mission to the International Space Station, targeted to launch June 13. Photo credit: NASA/Jack Pfaller

CAPE CANAVERAL, Fla. –– Seen on Launch Pads 39A and 39B at NASA's Kennedy Space Center in Florida are shuttles on both pads. At left is space shuttle Atlantis, poised for the STS-125 mission targeted to launch May 12, and at right is space shuttle Endeavour. Endeavour will be prepared on the pad for liftoff in the unlikely event that a rescue mission is necessary following space shuttle Atlantis' launch May 12 on the STS-125 mission to upgrade NASA's Hubble Space Telescope. After Atlantis is cleared to land, Endeavour will move to Launch Pad 39A for its upcoming STS-127 mission to the International Space Station, targeted to launch June 13. Photo credit: NASA/Jack Pfaller

CAPE CANAVERAL, Fla. – On Launch Pad 39A at NASA's Kennedy Space Center in Florida, technicians in the control booth get ready to roll the rotating service structure, or RSS, above them away from space shuttle Endeavour. First motion was at 10:39 a.m. EDT. The rollback is in preparation for Endeavour's liftoff June 13 on the STS-127 mission with a crew of seven. The rotating structure provides protected access to the shuttle for changeout and servicing of payloads at the pad. It is supported by a rotating bridge that pivots on a vertical axis on the west side of the pad's flame trench. After the RSS is rolled back, the orbiter is ready for fuel cell activation and external tank cryogenic propellant loading operations. The launch will be Endeavour's 23rd flight. The shuttle will carry the Japanese Experiment Module's Exposed Facility, or JEM-EF, and the Experiment Logistics Module-Exposed Section, or ELM-ES, on STS-127. The mission is the final of three flights dedicated to the assembly of the Japan Aerospace Exploration Agency's Kibo laboratory complex on the space station. Endeavour's launch is scheduled for June 13 at 7:17 a.m. EDT. Photo credit: NASA/Jim Grossmann

CAPE CANAVERAL, Fla. – Visible after rollback of the rotating service structure and looming like giants against the sky are the solid rocket boosters, external tank and space shuttle Endeavour, poised for launch on Launch Pad 39A at NASA's Kennedy Space Center in Florida. Near the top of Endeavour is the White Room, at the end of the orbiter access arm. The White Room provides entry into the shuttle for the astronauts. The rollback is preparation for Endeavour's liftoff June 13 on the STS-127 mission with a crew of seven. First motion was at 10:39 a.m. EDT and completed at 11:18 a.m. The rotating structure provides protected access to the shuttle for changeout and servicing of payloads at the pad. It is supported by a rotating bridge that pivots on a vertical axis on the west side of the pad's flame trench. After the RSS is rolled back, the orbiter is ready for fuel cell activation and external tank cryogenic propellant loading operations. The launch will be Endeavour's 23rd flight. The shuttle will carry the Japanese Experiment Module's Exposed Facility, or JEM-EF, and the Experiment Logistics Module-Exposed Section, or ELM-ES, on STS-127. The mission is the final of three flights dedicated to the assembly of the Japan Aerospace Exploration Agency's Kibo laboratory complex on the space station. Endeavour's launch is scheduled for June 13 at 7:17 a.m. EDT. Photo credit: NASA/Jim Grossmann

CAPE CANAVERAL, Fla. – On Launch Pad 39A at NASA's Kennedy Space Center in Florida, the oxygen vent hood, called the "beanie cap," is positioned above the external fuel tank of space shuttle Endeavour following the rollback of the rotating service structure, or RSS, at left. The beanie cap is designed to vent gaseous oxygen vapors away from the shuttle. The rollback is preparation for Endeavour's liftoff June 13 on the STS-127 mission with a crew of seven. First motion was at 10:39 a.m. EDT and completed at 11:18 a.m. The rotating structure provides protected access to the shuttle for changeout and servicing of payloads at the pad. It is supported by a rotating bridge that pivots on a vertical axis on the west side of the pad's flame trench. After the RSS is rolled back, the orbiter is ready for fuel cell activation and external tank cryogenic propellant loading operations. The launch will be Endeavour's 23rd flight. The shuttle will carry the Japanese Experiment Module's Exposed Facility, or JEM-EF, and the Experiment Logistics Module-Exposed Section, or ELM-ES, on STS-127. The mission is the final of three flights dedicated to the assembly of the Japan Aerospace Exploration Agency's Kibo laboratory complex on the space station. Endeavour's launch is scheduled for June 13 at 7:17 a.m. EDT. Photo credit: NASA/Jim Grossmann

CAPE CANAVERAL, Fla. – On Launch Pad 39A at NASA's Kennedy Space Center in Florida, space shuttle Endeavour is revealed after the rollback of the rotating service structure, or RSS. In the foreground is the flame trench, which the mobile launcher platform straddles. On top of the external fuel tank is the oxygen vent hood, called the "beanie cap," which is designed to vent gaseous oxygen vapors away from the shuttle. The rollback is preparation for Endeavour's liftoff June 13 on the STS-127 mission with a crew of seven. First motion was at 10:39 a.m. EDT and completed at 11:18 a.m. The rotating structure provides protected access to the shuttle for changeout and servicing of payloads at the pad. It is supported by a rotating bridge that pivots on a vertical axis on the west side of the pad's flame trench. After the RSS is rolled back, the orbiter is ready for fuel cell activation and external tank cryogenic propellant loading operations. The launch will be Endeavour's 23rd flight. The shuttle will carry the Japanese Experiment Module's Exposed Facility, or JEM-EF, and the Experiment Logistics Module-Exposed Section, or ELM-ES, on STS-127. The mission is the final of three flights dedicated to the assembly of the Japan Aerospace Exploration Agency's Kibo laboratory complex on the space station. Endeavour's launch is scheduled for June 13 at 7:17 a.m. EDT. Photo credit: NASA/Jim Grossmann

CAPE CANAVERAL, Fla. – The open rotating service structure, or RSS (left), on Launch Pad 39A at NASA's Kennedy Space Center in Florida reveals space shuttle Endeavour poised for launch. The RSS was rotated to its open position in preparation for Endeavour's liftoff June 13 on the STS-127 mission with a crew of seven. First motion was at 10:39 a.m. EDT and completed at 11:18 a.m. The rotating structure provides protected access to the shuttle for changeout and servicing of payloads at the pad. It is supported by a rotating bridge that pivots on a vertical axis on the west side of the pad's flame trench. After the RSS is rolled back, the orbiter is ready for fuel cell activation and external tank cryogenic propellant loading operations. The launch will be Endeavour's 23rd flight. The shuttle will carry the Japanese Experiment Module's Exposed Facility, or JEM-EF, and the Experiment Logistics Module-Exposed Section, or ELM-ES, on STS-127. The mission is the final of three flights dedicated to the assembly of the Japan Aerospace Exploration Agency's Kibo laboratory complex on the space station. Endeavour's launch is scheduled for June 13 at 7:17 a.m. EDT. Photo credit: NASA/Jim Grossmann

CAPE CANAVERAL, Fla. – On Launch Pad 39A at NASA's Kennedy Space Center in Florida, technicians in the control booth roll the rotating service structure, or RSS, away from space shuttle Endeavour. First motion was at 10:39 a.m. EDT. The rollback is in preparation for Endeavour's liftoff June 13 on the STS-127 mission with a crew of seven. The rotating structure provides protected access to the shuttle for changeout and servicing of payloads at the pad. It is supported by a rotating bridge that pivots on a vertical axis on the west side of the pad's flame trench. After the RSS is rolled back, the orbiter is ready for fuel cell activation and external tank cryogenic propellant loading operations. The launch will be Endeavour's 23rd flight. The shuttle will carry the Japanese Experiment Module's Exposed Facility, or JEM-EF, and the Experiment Logistics Module-Exposed Section, or ELM-ES, on STS-127. The mission is the final of three flights dedicated to the assembly of the Japan Aerospace Exploration Agency's Kibo laboratory complex on the space station. Endeavour's launch is scheduled for June 13 at 7:17 a.m. EDT. Photo credit: NASA/Jim Grossmann

CAPE CANAVERAL, Fla. – On Launch Pad 39A at NASA's Kennedy Space Center in Florida, space shuttle Endeavour is revealed after the rollback of the rotating service structure, or RSS. On the left of Endeavour is the White Room, at the end of the orbiter access arm. The White Room provides entry into the shuttle for the astronauts. The rollback is preparation for Endeavour's liftoff June 13 on the STS-127 mission with a crew of seven. First motion was at 10:39 a.m. EDT and completed at 11:18 a.m. The rotating structure provides protected access to the shuttle for changeout and servicing of payloads at the pad. It is supported by a rotating bridge that pivots on a vertical axis on the west side of the pad's flame trench. After the RSS is rolled back, the orbiter is ready for fuel cell activation and external tank cryogenic propellant loading operations. The launch will be Endeavour's 23rd flight. The shuttle will carry the Japanese Experiment Module's Exposed Facility, or JEM-EF, and the Experiment Logistics Module-Exposed Section, or ELM-ES, on STS-127. The mission is the final of three flights dedicated to the assembly of the Japan Aerospace Exploration Agency's Kibo laboratory complex on the space station. Endeavour's launch is scheduled for June 13 at 7:17 a.m. EDT. Photo credit: NASA/Jim Grossmann

CAPE CANAVERAL, Fla. – After rollback of the rotating service structure on Launch Pad 39A at NASA's Kennedy Space Center in Florida, space shuttle Endeavour, with its external fuel tank and solid rocket boosters, are poised for launch. The rollback is preparation for Endeavour's liftoff June 13 on the STS-127 mission with a crew of seven. First motion was at 10:39 a.m. EDT and completed at 11:18 a.m. The rotating structure provides protected access to the shuttle for changeout and servicing of payloads at the pad. It is supported by a rotating bridge that pivots on a vertical axis on the west side of the pad's flame trench. After the RSS is rolled back, the orbiter is ready for fuel cell activation and external tank cryogenic propellant loading operations. The launch will be Endeavour's 23rd flight. The shuttle will carry the Japanese Experiment Module's Exposed Facility, or JEM-EF, and the Experiment Logistics Module-Exposed Section, or ELM-ES, on STS-127. The mission is the final of three flights dedicated to the assembly of the Japan Aerospace Exploration Agency's Kibo laboratory complex on the space station. Endeavour's launch is scheduled for June 13 at 7:17 a.m. EDT. Photo credit: NASA/Jim Grossmann

CAPE CANAVERAL, Fla. – Just before dawn, space shuttle Endeavour is bathed in xenon lights after being secured on Launch Pad 39B at NASA's Kennedy Space Center in Florida. First motion on rollout from the Vehicle Assembly Building was at 11:57 p.m. EDT April 16. On either side of the pad are two of the new lightning towers erected for NASA's Constellation Program, which will use the pad for Ares rocket launches. Endeavour will be prepared on the pad for liftoff in the unlikely event that a rescue mission is necessary following space shuttle Atlantis' launch on the STS-125 mission to service NASA's Hubble Space Telescope. After Atlantis is cleared to land, Endeavour will move to Launch Pad 39A for its upcoming STS-127 mission to the International Space Station, targeted to launch June 13. Photo credit: NASA/Dimitri Gerondidakis

CAPE CANAVERAL, Fla. – On Launch Pad 39A at NASA's Kennedy Space Center in Florida, workers prepare to remove the 7-inch quick disconnect on the Ground Umbilical Carrier Plate, or GUCP, on space shuttle Endeavour's external fuel tank. A hydrogen leak at the location during tanking for the STS-127 mission caused the launch attempts to be scrubbed on June 13 and June 17. The GUCP will be examined to determine the cause of the hydrogen leak and repaired. The GUCP is the overboard vent to the pad and the flame stack where the vented hydrogen is burned off. Endeavour's next launch attempt is targeted for July 11 at 7:39 p.m. EDT. Photo credit: NASA/Jack Pfaller

CAPE CANAVERAL, Fla. – On Launch Pad 39A at NASA's Kennedy Space Center in Florida, workers remove the 7-inch quick disconnect on the Ground Umbilical Carrier Plate, or GUCP, on space shuttle Endeavour's external fuel tank. A hydrogen leak at the location during tanking for the STS-127 mission caused the launch attempts to be scrubbed on June 13 and June 17. The GUCP will be examined to determine the cause of the hydrogen leak and repaired. The GUCP is the overboard vent to the pad and the flame stack where the vented hydrogen is burned off. Endeavour's next launch attempt is targeted for July 11 at 7:39 p.m. EDT. Photo credit: NASA/Jack Pfaller

CAPE CANAVERAL, Fla. – The afternoon sun casts shadows on space shuttle Endeavour's external fuel tank as workers remove the seal from the Ground Umbilical Carrier Plate, or GUCP, on the tank. A hydrogen leak at the location during tanking for the STS-127 mission caused the launch attempts to be scrubbed on June 13 and June 17. The GUCP will be examined to determine the cause of the hydrogen leak and repaired. The GUCP is the overboard vent to the pad and the flame stack where the vented hydrogen is burned off. Endeavour's next launch attempt is targeted for July 11 at 7:39 p.m. EDT. Photo credit: NASA/Jack Pfaller

CAPE CANAVERAL, Fla. – On Launch Pad 39A at NASA's Kennedy Space Center in Florida, a worker has removed the seal from the Ground Umbilical Carrier Plate, or GUCP, on space shuttle Endeavour's external fuel tank. A hydrogen leak at the location during tanking for the STS-127 mission caused the launch attempts to be scrubbed on June 13 and June 17. The GUCP will be examined to determine the cause of the hydrogen leak and repaired. The GUCP is the overboard vent to the pad and the flame stack where the vented hydrogen is burned off. Endeavour's next launch attempt is targeted for July 11 at 7:39 p.m. EDT. Photo credit: NASA/Jack Pfaller

CAPE CANAVERAL, Fla. – On Launch Pad 39A at NASA's Kennedy Space Center in Florida, a worker has removed the seal from the Ground Umbilical Carrier Plate, or GUCP, on space shuttle Endeavour's external fuel tank. A hydrogen leak at the location during tanking for the STS-127 mission caused the launch attempts to be scrubbed on June 13 and June 17. The GUCP will be examined to determine the cause of the hydrogen leak and repaired. The GUCP is the overboard vent to the pad and the flame stack where the vented hydrogen is burned off. Endeavour's next launch attempt is targeted for July 11 at 7:39 p.m. EDT. Photo credit: NASA/Jack Pfaller

CAPE CANAVERAL, Fla. – On Launch Pad 39A at NASA's Kennedy Space Center in Florida, work continues on removing the Ground Umbilical Carrier Plate, or GUCP, on space shuttle Endeavour's external fuel tank. A hydrogen leak at the location during tanking for the STS-127 mission caused the launch attempts to be scrubbed on June 13 and June 17. The GUCP will be examined to determine the cause of the hydrogen leak and repaired. The GUCP is the overboard vent to the pad and the flame stack where the vented hydrogen is burned off. Endeavour's next launch attempt is targeted for July 11 at 7:39 p.m. EDT. Photo credit: NASA/Jack Pfaller

CAPE CANAVERAL, Fla. – On Launch Pad 39A at NASA's Kennedy Space Center in Florida, workers remove the 7-inch quick disconnect from the Ground Umbilical Carrier Plate, or GUCP, on space shuttle Endeavour's external fuel tank. A hydrogen leak at the location during tanking for the STS-127 mission caused the launch attempts to be scrubbed on June 13 and June 17. The GUCP will be examined to determine the cause of the hydrogen leak and repaired. The GUCP is the overboard vent to the pad and the flame stack where the vented hydrogen is burned off. Endeavour's next launch attempt is targeted for July 11 at 7:39 p.m. EDT. Photo credit: NASA/Jack Pfaller

CAPE CANAVERAL, Fla. – On Launch Pad 39A at NASA's Kennedy Space Center in Florida, a worker has removed the 7-inch quick disconnect from the Ground Umbilical Carrier Plate, or GUCP, on space shuttle Endeavour's external fuel tank. A hydrogen leak at the location during tanking for the STS-127 mission caused the launch attempts to be scrubbed on June 13 and June 17. The GUCP will be examined to determine the cause of the hydrogen leak and repaired. The GUCP is the overboard vent to the pad and the flame stack where the vented hydrogen is burned off. Endeavour's next launch attempt is targeted for July 11 at 7:39 p.m. EDT. Photo credit: NASA/Jack Pfaller

CAPE CANAVERAL, Fla. – On Launch Pad 39A at NASA's Kennedy Space Center in Florida, workers remove the 7-inch quick disconnect on the Ground Umbilical Carrier Plate, or GUCP, on space shuttle Endeavour's external fuel tank. A hydrogen leak at the location during tanking for the STS-127 mission caused the launch attempts to be scrubbed on June 13 and June 17. The GUCP will be examined to determine the cause of the hydrogen leak and repaired. The GUCP is the overboard vent to the pad and the flame stack where the vented hydrogen is burned off. Endeavour's next launch attempt is targeted for July 11 at 7:39 p.m. EDT. Photo credit: NASA/Jack Pfaller

CAPE CANAVERAL, Fla. – On Launch Pad 39A at NASA's Kennedy Space Center in Florida, a worker examines the location of the quick disconnect on the Ground Umbilical Carrier Plate, or GUCP, being removed from space shuttle Endeavour's external fuel tank. A hydrogen leak at the location during tanking for the STS-127 mission caused the launch attempts to be scrubbed on June 13 and June 17. The GUCP will be examined to determine the cause of the hydrogen leak and repaired. The GUCP is the overboard vent to the pad and the flame stack where the vented hydrogen is burned off. Endeavour's next launch attempt is targeted for July 11 at 7:39 p.m. EDT. Photo credit: NASA/Jack Pfaller

CAPE CANAVERAL, Fla. – On Launch Pad 39A at NASA's Kennedy Space Center in Florida, workers prepare to remove the seal from the Ground Umbilical Carrier Plate, or GUCP, on space shuttle Endeavour's external fuel tank. A hydrogen leak at the location during tanking for the STS-127 mission caused the launch attempts to be scrubbed on June 13 and June 17. The GUCP will be examined to determine the cause of the hydrogen leak and repaired. The GUCP is the overboard vent to the pad and the flame stack where the vented hydrogen is burned off. Endeavour's next launch attempt is targeted for July 11 at 7:39 p.m. EDT. Photo credit: NASA/Jack Pfaller

CAPE CANAVERAL, Fla. – On Launch Pad 39A at NASA's Kennedy Space Center in Florida, a worker removes the seal from the Ground Umbilical Carrier Plate, or GUCP, on space shuttle Endeavour's external fuel tank. A hydrogen leak at the location during tanking for the STS-127 mission caused the launch attempts to be scrubbed on June 13 and June 17. The GUCP will be examined to determine the cause of the hydrogen leak and repaired. The GUCP is the overboard vent to the pad and the flame stack where the vented hydrogen is burned off. Endeavour's next launch attempt is targeted for July 11 at 7:39 p.m. EDT. Photo credit: NASA/Jack Pfaller

CAPE CANAVERAL, Fla. – On Launch Pad 39A at NASA's Kennedy Space Center in Florida, workers remove the 7-inch quick disconnect on the Ground Umbilical Carrier Plate, or GUCP, on space shuttle Endeavour's external fuel tank. A hydrogen leak at the location during tanking for the STS-127 mission caused the launch attempts to be scrubbed on June 13 and June 17. The GUCP will be examined to determine the cause of the hydrogen leak and repaired. The GUCP is the overboard vent to the pad and the flame stack where the vented hydrogen is burned off. Endeavour's next launch attempt is targeted for July 11 at 7:39 p.m. EDT. Photo credit: NASA/Jack Pfaller

CAPE CANAVERAL, Fla. –– Space shuttle Atlantis atop the mobile launcher platform straddles the flame trench on Launch Pad 39A at NASA's Kennedy Space Center in Florida. It is joined by space shuttle Endeavour on Launch Pad 39B. This is probably the final time two shuttles will be on launch pads at the same time with the space shuttle fleet set for retirement in 2010. Endeavour will be prepared on the pad for liftoff in the unlikely event that a rescue mission is necessary following space shuttle Atlantis' launch on the STS-125 mission to service NASA's Hubble Space Telescope. After Atlantis is cleared to land, Endeavour will move to Launch Pad 39A for its upcoming STS-127 mission to the International Space Station, targeted to launch June 13. Photo credit: NASA/Dimitri Gerondidakis

CAPE CANAVERAL, Fla. –– Dawn rises over the Atlantic Ocean behind space shuttle Endeavour on Launch Pad 39B at NASA's Kennedy Space Center in Florida. Surrounding the pad are the lightning towers erected for NASA's Constellation Program, which will use the pad for Ares rocket launches. Endeavour has joined space shuttle Atlantis, which is on pad 39A. This is probably the final time two shuttles will be on launch pads at the same time with the space shuttle fleet set for retirement in 2010. Endeavour will be prepared on the pad for liftoff in the unlikely event that a rescue mission is necessary following space shuttle Atlantis' launch on the STS-125 mission to service NASA's Hubble Space Telescope. After Atlantis is cleared to land, Endeavour will move to Launch Pad 39A for its upcoming STS-127 mission to the International Space Station, targeted to launch June 13. Photo credit: NASA/Dimitri Gerondidakis

CAPE CANAVERAL, Fla. –– Sunlight spotlights space shuttle Atlantis (left) and space shuttle Endeavour on Launch Pads 39A and 39B, respectively, at NASA's Kennedy Space Center in Florida. This is probably the final time two shuttles will be on launch pads at the same time with the space shuttle fleet set for retirement in 2010. Endeavour will be prepared on the pad for liftoff in the unlikely event that a rescue mission is necessary following space shuttle Atlantis' launch on the STS-125 mission to service NASA's Hubble Space Telescope. After Atlantis is cleared to land, Endeavour will move to Launch Pad 39A for its upcoming STS-127 mission to the International Space Station, targeted to launch June 13. Photo credit: NASA/Dimitri Gerondidakis

CAPE CANAVERAL, Fla. –– Launch Pads 39A and 39B at NASA's Kennedy Space Center in Florida are ablaze with lights before dawn, showing shuttles on both pads. At left is space shuttle Atlantis, poised for the STS-125 mission targeted to launch May 12, and at right is space shuttle Endeavour. Endeavour will be prepared on the pad for liftoff in the unlikely event that a rescue mission is necessary following Atlantis' launch. After Atlantis is cleared to land, Endeavour will move to Launch Pad 39A for its upcoming STS-127 mission to the International Space Station, targeted to launch June 13. Photo credit: NASA/Chris Rhodes

CAPE CANAVERAL, Fla. –– On Launch Pad 39B (left) at NASA's Kennedy Space Center in Florida, space shuttle Endeavour has joined space shuttle Atlantis on Launch Pad 39A. This is probably the final time two shuttles will be on launch pads at the same time with the space shuttle fleet set for retirement in 2010. Endeavour will be prepared on the pad for liftoff in the unlikely event that a rescue mission is necessary following space shuttle Atlantis' launch on the STS-125 mission to service NASA's Hubble Space Telescope. After Atlantis is cleared to land, Endeavour will move to Launch Pad 39A for its upcoming STS-127 mission to the International Space Station, targeted to launch June 13. Photo credit: NASA/Dimitri Gerondidakis

CAPE CANAVERAL, Fla. –– On Launch Pad 39B (left) at NASA's Kennedy Space Center in Florida, space shuttle Endeavour has joined space shuttle Atlantis on Launch Pad 39A (right). This is probably the final time two shuttles will be on launch pads at the same time with the space shuttle fleet set for retirement in 2010. Surrounding pad 39B are the lightning towers erected for NASA's Constellation Program, which will use the pad for Ares rocket launches. Endeavour will be prepared on the pad for liftoff in the unlikely event that a rescue mission is necessary following space shuttle Atlantis' launch on the STS-125 mission to service NASA's Hubble Space Telescope. After Atlantis is cleared to land, Endeavour will move to Launch Pad 39A for its upcoming STS-127 mission to the International Space Station, targeted to launch June 13. Photo credit: NASA/Dimitri Gerondidakis

CAPE CANAVERAL, Fla. –– At NASA's Kennedy Space Center in Florida, space shuttles Atlantis (left) and Endeavour (right) are seen on Launch Pad 39A and 39B respectively. With the space shuttle fleet set for retirement in 2010, this is expected to be the final time two shuttles will be on launch pads at the same time. Endeavour will stand by at pad B in the unlikely event that a rescue mission is necessary during Atlantis' upcoming mission to upgrade NASA's Hubble Space Telescope. Atlantis is targeted to launch May 12. After Endeavour is cleared from its duty as a rescue spacecraft, it will be moved to Launch Pad 39A for its STS-127 mission to the International Space Station. That flight is targeted for launch June 13. Photo credit: NASA/Kim Shiflett

CAPE CANAVERAL, Fla. –– Space shuttle Endeavour is silhouetted against the dawn pink sky on Launch Pad 39B at NASA's Kennedy Space Center in Florida. Surrounding the pad are the lightning towers erected for NASA's Constellation Program, which will use the pad for Ares rocket launches. Dotting the still dark sky at upper right is the moon. Endeavour will be prepared on the pad for liftoff in the unlikely event that a rescue mission is necessary following space shuttle Atlantis' launch May 12 on the STS-125 mission to upgrade NASA's Hubble Space Telescope. After Atlantis is cleared to land, Endeavour will move to Launch Pad 39A for its upcoming STS-127 mission to the International Space Station, targeted to launch June 13. Photo credit: NASA/Jack Pfaller

CAPE CANAVERAL, Fla. –– Early morning light falls on space shuttle Endeavour on Launch Pad 39B at NASA's Kennedy Space Center in Florida. It joins space shuttle Atlantis on Launch Pad 39A. This is probably the final time two shuttles will be on launch pads at the same time with the space shuttle fleet set for retirement in 2010. Endeavour will be prepared on the pad for liftoff in the unlikely event that a rescue mission is necessary following space shuttle Atlantis' launch on the STS-125 mission to service NASA's Hubble Space Telescope. After Atlantis is cleared to land, Endeavour will move to Launch Pad 39A for its upcoming STS-127 mission to the International Space Station, targeted to launch June 13. Photo credit: NASA/Dimitri Gerondidakis

CAPE CANAVERAL, Fla. –– Dawn breaks over the Atlantic Ocean behind space shuttle Atlantis on Launch Pad 39A at NASA's Kennedy Space Center in Florida. Atlantis is targeted to launch May 12 on its STS-125 mission. Space shuttle Endeavour sits on Launch Pad 39B, probably the final time two shuttles will be on launch pads at the same time with the space shuttle fleet set for retirement in 2010. Endeavour will be prepared on the pad for liftoff in the unlikely event that a rescue mission is necessary following space shuttle Atlantis' launch on the STS-125 mission to service NASA's Hubble Space Telescope. After Atlantis is cleared to land, Endeavour will move to Launch Pad 39A for its upcoming STS-127 mission to the International Space Station, targeted to launch June 13. Photo credit: NASA/Dimitri Gerondidakis

CAPE CANAVERAL, Fla. –– On Launch Pad 39B at NASA's Kennedy Space Center in Florida, space shuttle Endeavour has joined space shuttle Atlantis on Launch Pad 39A. In the background is the Atlantic Ocean. This is probably the final time two shuttles will be on launch pads at the same time with the space shuttle fleet set for retirement in 2010. Endeavour will be prepared on the pad for liftoff in the unlikely event that a rescue mission is necessary following space shuttle Atlantis' launch on the STS-125 mission to service NASA's Hubble Space Telescope. After Atlantis is cleared to land, Endeavour will move to Launch Pad 39A for its upcoming STS-127 mission to the International Space Station, targeted to launch June 13. Photo credit: NASA/Dimitri Gerondidakis

CAPE CANAVERAL, Fla. –– Space shuttle Endeavour is silhouetted against the dawn pink sky on Launch Pad 39B at NASA's Kennedy Space Center in Florida. Surrounding the pad are the lightning towers erected for NASA's Constellation Program, which will use the pad for Ares rocket launches. Dotting the dark blue sky at upper right is the moon. Endeavour will be prepared on the pad for liftoff in the unlikely event that a rescue mission is necessary following space shuttle Atlantis' launch May 12 on the STS-125 mission to upgrade NASA's Hubble Space Telescope. After Atlantis is cleared to land, Endeavour will move to Launch Pad 39A for its upcoming STS-127 mission to the International Space Station, targeted to launch June 13. Photo credit: NASA/Jack Pfaller

CAPE CANAVERAL, Fla. –– Space shuttle Atlantis atop the mobile launcher platform straddles the flame trench on Launch Pad 39A at NASA's Kennedy Space Center in Florida. Behind it is the Atlantic Ocean. Atlantis has been joined by space shuttle Endeavour on Launch Pad 39B. This is probably the final time two shuttles will be on launch pads at the same time with the space shuttle fleet set for retirement in 2010. Endeavour will be prepared on the pad for liftoff in the unlikely event that a rescue mission is necessary following space shuttle Atlantis' launch on the STS-125 mission to service NASA's Hubble Space Telescope. After Atlantis is cleared to land, Endeavour will move to Launch Pad 39A for its upcoming STS-127 mission to the International Space Station, targeted to launch June 13. Photo credit: NASA/Dimitri Gerondidakis

CAPE CANAVERAL, Fla. –– Sunlight spotlights space shuttle Atlantis (left) and space shuttle Endeavour on Launch Pads 39A and 39B, respectively, at NASA's Kennedy Space Center in Florida. This is probably the final time two shuttles will be on launch pads at the same time with the space shuttle fleet set for retirement in 2010. Endeavour will be prepared on the pad for liftoff in the unlikely event that a rescue mission is necessary following space shuttle Atlantis' launch on the STS-125 mission to service NASA's Hubble Space Telescope. After Atlantis is cleared to land, Endeavour will move to Launch Pad 39A for its upcoming STS-127 mission to the International Space Station, targeted to launch June 13. Photo credit: NASA/Dimitri Gerondidakis

CAPE CANAVERAL, Fla. –– Viewed across the lagoon at NASA's Kennedy Space Center in Florida, space shuttle Endeavour is poised on Launch Pad 39B. Surrounding the pad are the lightning towers erected for NASA's Constellation Program, which will use the pad for Ares rocket launches. Endeavour will be prepared on the pad for liftoff in the unlikely event that a rescue mission is necessary following space shuttle Atlantis' launch May 12 on the STS-125 mission to upgrade NASA's Hubble Space Telescope. After Atlantis is cleared to land, Endeavour will move to Launch Pad 39A for its upcoming STS-127 mission to the International Space Station, targeted to launch June 13. Photo credit: NASA/Jack Pfaller

CAPE CANAVERAL, Fla. –– Under a dawn sky, space shuttle Endeavour is still bathed in light from the fixed service structure. Endeavour joins Atlantis, which is on Launch Pad 39A at NASA's Kennedy Space Center in Florida. The towers around the launch pad were erected for NASA's Constellation Program, which will use the pad for Ares rocket launches. With the space shuttle fleet set for retirement in 2010, this is expected to be the final time two shuttles will be on launch pads at the same time. Endeavour will be prepared on the pad for liftoff in the unlikely event that a rescue mission is necessary following space shuttle Atlantis' launch on the STS-125 mission to service NASA's Hubble Space Telescope. After Atlantis is cleared to land, Endeavour will move to Launch Pad 39A for its upcoming STS-127 mission to the International Space Station, targeted to launch June 13. Photo credit: NASA/Dimitri Gerondidakis

CAPE CANAVERAL, Fla. –– Space shuttle Atlantis (left) and space shuttle Endeavour are seen on Launch Pads 39A and 39B, respectively, at NASA's Kennedy Space Center in Florida. This is probably the final time two shuttles will be on launch pads at the same time with the space shuttle fleet set for retirement in 2010. Surrounding the pad are the lightning towers erected for NASA's Constellation Program, which will use the pad for Ares rocket launches. Endeavour will be prepared on the pad for liftoff in the unlikely event that a rescue mission is necessary following space shuttle Atlantis' launch on the STS-125 mission to service NASA's Hubble Space Telescope. After Atlantis is cleared to land, Endeavour will move to Launch Pad 39A for its upcoming STS-127 mission to the International Space Station, targeted to launch June 13. Photo credit: NASA/Dimitri Gerondidakis

CAPE CANAVERAL, Fla. –– Early dawn showcases Launch Pads 39A and 39B at NASA's Kennedy Space Center in Florida with shuttles on both pads. At left is space shuttle Atlantis, poised for the STS-125 mission targeted to launch May 12, and at right is space shuttle Endeavour. Endeavour will be prepared on the pad for liftoff in the unlikely event that a rescue mission is necessary following Atlantis' launch. After Atlantis is cleared to land, Endeavour will move to Launch Pad 39A for its upcoming STS-127 mission to the International Space Station, targeted to launch June 13. Photo credit: NASA/Chris Rhodes

CAPE CANAVERAL, Fla. –– Space shuttle Atlantis atop the mobile launcher platform sits on Launch Pad 39A at NASA's Kennedy Space Center in Florida. At left is the Vehicle Assembly Building. Atlantis has been joined by space shuttle Endeavour on Launch Pad 39B. This is probably the final time two shuttles will be on launch pads at the same time with the space shuttle fleet set for retirement in 2010. Endeavour will be prepared on the pad for liftoff in the unlikely event that a rescue mission is necessary following space shuttle Atlantis' launch on the STS-125 mission to service NASA's Hubble Space Telescope. After Atlantis is cleared to land, Endeavour will move to Launch Pad 39A for its upcoming STS-127 mission to the International Space Station, targeted to launch June 13. Photo credit: NASA/Dimitri Gerondidakis

CAPE CANAVERAL, Fla. –– Space shuttle Atlantis (left) and space shuttle Endeavour are seen on Launch Pads 39A and 39B, respectively, at NASA's Kennedy Space Center in Florida. This is probably the final time two shuttles will be on launch pads at the same time with the space shuttle fleet set for retirement in 2010. Surrounding pad 39B are the lightning towers erected for NASA's Constellation Program, which will use the pad for Ares rocket launches. Endeavour will be prepared on the pad for liftoff in the unlikely event that a rescue mission is necessary following space shuttle Atlantis' launch on the STS-125 mission to service NASA's Hubble Space Telescope. After Atlantis is cleared to land, Endeavour will move to Launch Pad 39A for its upcoming STS-127 mission to the International Space Station, targeted to launch June 13. Photo credit: NASA/Dimitri Gerondidakis

CAPE CANAVERAL, Fla. –– Space shuttle Endeavour (left) and space shuttle Atlantis are seen on Launch Pads 39B and 39A, respectively, at NASA's Kennedy Space Center in Florida. This is probably the final time two shuttles will be on launch pads at the same time with the space shuttle fleet set for retirement in 2010. Endeavour will be prepared on the pad for liftoff in the unlikely event that a rescue mission is necessary following space shuttle Atlantis' launch on the STS-125 mission to service NASA's Hubble Space Telescope. After Atlantis is cleared to land, Endeavour will move to Launch Pad 39A for its upcoming STS-127 mission to the International Space Station, targeted to launch June 13. Photo credit: NASA/Dimitri Gerondidakis

CAPE CANAVERAL, Fla. –– On Launch Pad 39B at NASA's Kennedy Space Center in Florida, space shuttle Endeavour has joined space shuttle Atlantis on Launch Pad 39A. In the background is the Atlantic Ocean. This is probably the final time two shuttles will be on launch pads at the same time with the space shuttle fleet set for retirement in 2010. Endeavour will be prepared on the pad for liftoff in the unlikely event that a rescue mission is necessary following space shuttle Atlantis' launch on the STS-125 mission to service NASA's Hubble Space Telescope. After Atlantis is cleared to land, Endeavour will move to Launch Pad 39A for its upcoming STS-127 mission to the International Space Station, targeted to launch June 13. Photo credit: NASA/Dimitri Gerondidakis

CAPE CANAVERAL, Fla. –– As dawn begins to brighten the sky over Launch Pad 39B at NASA's Kennedy Space Center in Florida, space shuttle Endeavour is seen bathed in lights from the fixed service structure. Endeavour joins Atlantis, which is on Launch Pad 39A. The towers around the launch pad were erected for NASA's Constellation Program, which will use the pad for Ares rocket launches. With the space shuttle fleet set for retirement in 2010, this is expected to be the final time two shuttles will be on launch pads at the same time. Endeavour will be prepared on the pad for liftoff in the unlikely event that a rescue mission is necessary following space shuttle Atlantis' launch on the STS-125 mission to service NASA's Hubble Space Telescope. After Atlantis is cleared to land, Endeavour will move to Launch Pad 39A for its upcoming STS-127 mission to the International Space Station, targeted to launch June 13. Photo credit: NASA/Dimitri Gerondidakis

CAPE CANAVERAL, Fla. –– Space shuttle Endeavour (left) and space shuttle Atlantis are seen on Launch Pads 39B and 39A, respectively, at NASA's Kennedy Space Center. This is probably the final time two shuttles will be on launch pads at the same time with the space shuttle fleet set for retirement in 2010.Endeavour will be prepared on the pad for liftoff in the unlikely event that a rescue mission is necessary following space shuttle Atlantis' launch on the STS-125 mission to service NASA's Hubble Space Telescope. After Atlantis is cleared to land, Endeavour will move to Launch Pad 39A for its upcoming STS-127 mission to the International Space Station, targeted to launch June 13. Photo credit: NASA/Dimitri Gerondidakis

CAPE CANAVERAL, Fla. –– Space shuttle Atlantis (left) and space shuttle Endeavour are seen on Launch Pads 39A and 39B, respectively, at NASA's Kennedy Space Center in Florida. This is probably the final time two shuttles will be on launch pads at the same time with the space shuttle fleet set for retirement in 2010. Surrounding pad 39B are the lightning towers erected for NASA's Constellation Program, which will use the pad for Ares rocket launches. Endeavour will be prepared on the pad for liftoff in the unlikely event that a rescue mission is necessary following space shuttle Atlantis' launch on the STS-125 mission to service NASA's Hubble Space Telescope. After Atlantis is cleared to land, Endeavour will move to Launch Pad 39A for its upcoming STS-127 mission to the International Space Station, targeted to launch June 13. Photo credit: NASA/Dimitri Gerondidakis

CAPE CANAVERAL, Fla. –– As dawn begins to brighten the sky over Launch Pad 39B at NASA's Kennedy Space Center in Florida, space shuttle Endeavour is seen bathed in lights from the fixed service structure. Endeavour joins Atlantis, which is on Launch Pad 39A. With the space shuttle fleet set for retirement in 2010, this is expected to be the final time two shuttles will be on launch pads at the same time. Endeavour will be prepared on the pad for liftoff in the unlikely event that a rescue mission is necessary following space shuttle Atlantis' launch on the STS-125 mission to service NASA's Hubble Space Telescope. After Atlantis is cleared to land, Endeavour will move to Launch Pad 39A for its upcoming STS-127 mission to the International Space Station, targeted to launch June 13. Photo credit: NASA/Dimitri Gerondidakis

The space shuttle Endeavour is seen at launch pad 39A at NASA's Kennedy Space Center in Cape Canaveral, Florida on Saturday, July 11, 2009. NASA is hopeful that Endeavour will launch with the crew of STS-127 on Sunday. Photo Credit: (NASA/Bill Ingalls)

The space shuttle Endeavour and its crew land, Friday, July 31, 2009 at NASA's Kennedy Space Center in Cape Canaveral, Florida, completing a 16-day journey of more than 6.5 million miles. Endeavour delivered the final segment to the Japan Aerospace Exploration Agency's Kibo laboratory and a new crew member to the International Space Station. Photo Credit: (NASA/Bill Ingalls)

The space shuttle Endeavour is seen at launch pad 39A at NASA's Kennedy Space Center in Cape Canaveral, Florida on Saturday, July 11, 2009. NASA is hopeful that Endeavour will launch with the crew of STS-127 on Sunday. Photo Credit: (NASA/Bill Ingalls)

Astronaut Mark Polansky, STS-127 mission commander, poses for a photograph by the front wheel of the space shuttle Endeavour shortly after it and its crew landed, Friday, July 31, 2009 at NASA's Kennedy Space Center in Cape Canaveral, Fla., completing a 16-day journey of more than 6.5 million miles. Endeavour delivered the final segment to the Japan Aerospace Exploration Agency's Kibo laboratory and a new crew member to the International Space Station. Photo Credit: (NASA/Bill Ingalls)

CAPE CANAVERAL, Fla. -- In the Space Station Processing Facility at NASA's Kennedy Space Center in Florida, an overhead crane lowers the ICS Exposed Facility, or ICS-EF, onto the Japanese Experiment Module's Experiment Logistics Module-Exposed Section, or ELM-ES, for installation. The ICS-EF is composed of several components, including an antenna, pointing mechanism, frequency converters, high-power amplifier and various sensors including the Earth sensor, Sun sensor and inertial reference unit. The ICS-EF is part of space shuttle Endeavour's payload on the STS-127 mission, targeted for launch on May 15. Photo credit: NASA/Jim Grossmann

CAPE CANAVERAL, Fla. -- In the Space Station Processing Facility at NASA's Kennedy Space Center in Florida, the ICS Exposed Facility, or ICS-EF, is lifted from its stand. It will be installed on the Japanese Experiment Module's Experiment Logistics Module-Exposed Section, or ELM-ES. The ICS-EF is composed of several components, including an antenna, pointing mechanism, frequency converters, high-power amplifier and various sensors including the Earth sensor, Sun sensor and inertial reference unit. The ICS-EF is part of space shuttle Endeavour's payload on the STS-127 mission, targeted for launch on May 15. Photo credit: NASA/Jim Grossmann

CAPE CANAVERAL, Fla. -- In the Space Station Processing Facility at NASA's Kennedy Space Center in Florida, workers examine the ICS Exposed Facility, or ICS-EF, after it is lifted from its stand. It will be installed on the Japanese Experiment Module's Experiment Logistics Module-Exposed Section, or ELM-ES. The ICS-EF is composed of several components, including an antenna, pointing mechanism, frequency converters, high-power amplifier and various sensors including the Earth sensor, Sun sensor and inertial reference unit. The ICS-EF is part of space shuttle Endeavour's payload on the STS-127 mission, targeted for launch on May 15. Photo credit: NASA/Jim Grossmann

CAPE CANAVERAL, Fla. -- In the Space Station Processing Facility at NASA's Kennedy Space Center in Florida, an overhead crane lowers the ICS Exposed Facility, or ICS-EF, onto the Japanese Experiment Module's Experiment Logistics Module-Exposed Section, or ELM-ES, for installation. It is being placed next to two other payloads, the SEDA-AP (Space Environment Data Acquisition Equipment-Attached Payload) and MAXI (Monitor of All-sky X-ray Image). The ICS-EF is part of space shuttle Endeavour's payload on the STS-127 mission, targeted for launch on May 15. Photo credit: NASA/Jim Grossmann

CAPE CANAVERAL, Fla. -- In the Space Station Processing Facility at NASA's Kennedy Space Center in Florida, workers prepare the ICS Exposed Facility, ICS-EF, to be lifted and installed on the Japanese Experiment Module's Experiment Logistics Module-Exposed Section, or ELM-ES. The ICS-EF is composed of several components, including an antenna, pointing mechanism, frequency converters, high-power amplifier and various sensors including the Earth sensor, Sun sensor and inertial reference unit. The ICS-EF is part of space shuttle Endeavour's payload on the STS-127 mission, targeted for launch on May 15. Photo credit: NASA/Jim Grossmann

CAPE CANAVERAL, Fla. -- In the Space Station Processing Facility at NASA's Kennedy Space Center in Florida, the ICS Exposed Facility, or ICS-EF, is moved across the floor to the Japanese Experiment Module's Experiment Logistics Module-Exposed Section, or ELM-ES, where it will be installed alongside two other payloads, the SEDA-AP (Space Environment Data Acquisition Equipment-Attached Payload) and MAXI (Monitor of All-sky X-ray Image), already installed. The ICS-EF is composed of several components, including an antenna, pointing mechanism, frequency converters, high-power amplifier and various sensors including the Earth sensor, Sun sensor and inertial reference unit. The ICS-EF is part of space shuttle Endeavour's payload on the STS-127 mission, targeted for launch on May 15. Photo credit: NASA/Jim Grossmann

CAPE CANAVERAL, Fla. -- In the Space Station Processing Facility at NASA's Kennedy Space Center in Florida, an overhead crane lowers the ICS Exposed Facility, or ICS-EF, onto the Japanese Experiment Module's Experiment Logistics Module-Exposed Section, or ELM-ES, where it will be installed alongside two other payloads, the SEDA-AP (Space Environment Data Acquisition Equipment-Attached Payload) and MAXI (Monitor of All-sky X-ray Image). The ICS-EF is composed of several components, including an antenna, pointing mechanism, frequency converters, high-power amplifier and various sensors including the Earth sensor, Sun sensor and inertial reference unit. The ICS-EF is part of space shuttle Endeavour's payload on the STS-127 mission, targeted for launch on May 15. Photo credit: NASA/Jim Grossmann

CAPE CANAVERAL, Fla. – After space shuttle Endeavour's rollout to Launch pad 39B at NASA's Kennedy Space Center in Florida this morning, two different shuttles are poised on two different launch pads. Shuttle Atlantis (left) already was on Launch Pad 39A. With the space shuttle fleet set for retirement in 2010, this is expected to be the final time two shuttles will be on launch pads at the same time. Endeavour will stand by at pad B in the unlikely event that a rescue mission is necessary during Atlantis' upcoming mission to upgrade NASA's Hubble Space Telescope. Atlantis is targeted to launch May 12. After Endeavour is cleared from its duty as a rescue spacecraft, it will be moved to Launch Pad 39A for its STS-127 mission to the International Space Station. That flight is targeted for launch June 13. Photo credit: NASA/Dimitri Gerondidakis

CAPE CANAVERAL, Fla. – After space shuttle Endeavour's rollout to Launch pad 39B at NASA's Kennedy Space Center in Florida this morning, two different shuttles are poised on two different launch pads. Shuttle Atlantis (foreground) already was on Launch Pad 39A. With the space shuttle fleet set for retirement in 2010, this is expected to be the final time two shuttles will be on launch pads at the same time. Endeavour will stand by at pad B in the unlikely event that a rescue mission is necessary during Atlantis' upcoming mission to upgrade NASA's Hubble Space Telescope. Atlantis is targeted to launch May 12. After Endeavour is cleared from its duty as a rescue spacecraft, it will be moved to Launch Pad 39A for its STS-127 mission to the International Space Station. That flight is targeted for launch June 13. Photo credit: NASA/Dimitri Gerondidakis

CAPE CANAVERAL, Fla. – On Launch Pad 39A at NASA's Kennedy Space Center in Florida, the rotating service structure around space shuttle Atlantis begins to open to enable delivery and transfer of Atlantis' payload on April 18. After space shuttle Endeavour's rollout to Launch pad 39B at NASA's Kennedy Space Center in Florida this morning, two different shuttles now are poised on two different launch pads in full view. With the space shuttle fleet set for retirement in 2010, this is expected to be the final time two shuttles will be on launch pads at the same time. Endeavour will stand by at pad B in the unlikely event that a rescue mission is necessary during space shuttle Atlantis' upcoming mission. Atlantis is targeted to launch May 12. After Endeavour is cleared from its duty as a rescue spacecraft, it will be moved to Launch Pad 39A for its STS-127 mission to the International Space Station. That flight is targeted for launch June 13. Photo credit: NASA/Kim Shiflett

CAPE CANAVERAL, Fla. – After space shuttle Endeavour's rollout to Launch pad 39B at NASA's Kennedy Space Center in Florida this morning, two different shuttles are poised on two different launch pads. Shuttle Atlantis (left) already was on Launch Pad 39A. With the space shuttle fleet set for retirement in 2010, this is expected to be the final time two shuttles will be on launch pads at the same time. Endeavour will stand by at pad B in the unlikely event that a rescue mission is necessary during Atlantis' upcoming mission to upgrade NASA's Hubble Space Telescope. Atlantis is targeted to launch May 12. After Endeavour is cleared from its duty as a rescue spacecraft, it will be moved to Launch Pad 39A for its STS-127 mission to the International Space Station. That flight is targeted for launch June 13. Photo credit: NASA/Kim Shiflett

CAPE CANAVERAL, Fla. – After space shuttle Endeavour's rollout to Launch pad 39B at NASA's Kennedy Space Center in Florida this morning, two different shuttles are poised on two different launch pads. Shuttle Atlantis (right) already was on Launch Pad 39A. With the space shuttle fleet set for retirement in 2010, this is expected to be the final time two shuttles will be on launch pads at the same time. Endeavour will stand by at pad B in the unlikely event that a rescue mission is necessary during Atlantis' upcoming mission to upgrade NASA's Hubble Space Telescope. Atlantis is targeted to launch May 12. After Endeavour is cleared from its duty as a rescue spacecraft, it will be moved to Launch Pad 39A for its STS-127 mission to the International Space Station. That flight is targeted for launch June 13. Photo credit: NASA/Kim Shiflett

CAPE CANAVERAL, Fla. – After space shuttle Endeavour's rollout to Launch pad 39B at NASA's Kennedy Space Center in Florida this morning, two different shuttles are poised on two different launch pads. Shuttle Atlantis (left) already was on Launch Pad 39A. With the space shuttle fleet set for retirement in 2010, this is expected to be the final time two shuttles will be on launch pads at the same time. Endeavour will stand by at pad B in the unlikely event that a rescue mission is necessary during Atlantis' upcoming mission to upgrade NASA's Hubble Space Telescope. Atlantis is targeted to launch May 12. After Endeavour is cleared from its duty as a rescue spacecraft, it will be moved to Launch Pad 39A for its STS-127 mission to the International Space Station. That flight is targeted for launch June 13. Photo credit: NASA/Dimitri Gerondidakis

CAPE CANAVERAL, Fla. – After space shuttle Endeavour's rollout to Launch pad 39B at NASA's Kennedy Space Center in Florida this morning, two different shuttles are poised on two different launch pads. Shuttle Atlantis (foreground) already was on Launch Pad 39A. With the space shuttle fleet set for retirement in 2010, this is expected to be the final time two shuttles will be on launch pads at the same time. Endeavour will stand by at pad B in the unlikely event that a rescue mission is necessary during Atlantis' upcoming mission to upgrade NASA's Hubble Space Telescope. Atlantis is targeted to launch May 12. After Endeavour is cleared from its duty as a rescue spacecraft, it will be moved to Launch Pad 39A for its STS-127 mission to the International Space Station. That flight is targeted for launch June 13. Photo credit: NASA/Dimitri Gerondidakis

NASA Administrator Charles Bolden, left, STS-127 mission commander Mark Polansky, and NASA Kennedy Space Center Director Bob Cabana, right, walk around the space shuttle Endeavour shortly after it and its crew landed, Friday, July 31, 2009 at NASA's Kennedy Space Center in Cape Canaveral, Fla., completing a 16-day journey of more than 6.5 million miles. Endeavour delivered the final segment to the Japan Aerospace Exploration Agency's Kibo laboratory and a new crew member to the International Space Station. Photo Credit: (NASA/Bill Ingalls)

The space shuttle Endeavour is framed by a windsock at launch pad 39A at the NASA Kennedy Space Center in Cape Canaveral, Florida on Saturday, July 11, 2009. NASA is hopeful that Endeavour will launch with the crew of STS-127 on Sunday. Photo Credit: (NASA/Bill Ingalls)

Storm clouds approach Launch Pad 39A at NASA's Kennedy Space Center in Florida on Friday, July 10, 2009 as space shuttle Endeavour stands awaiting Saturday's planned launch of the STS-127 mission. Photo Credit: (NASA/Bill Ingalls)

NASA Kennedy Space Center Director Bob Cabana, left, and NASA Administrator Charles Bolden walk to welcome home the crew of the space shuttle Endeavour shortly after it and its crew landed, Friday, July 31, 2009 at NASA's Kennedy Space Center in Cape Canaveral, Florida, completing a 16-day journey of more than 6.5 million miles. Endeavour delivered the final segment to the Japan Aerospace Exploration Agency's Kibo laboratory and a new crew member to the International Space Station.

NASA Kennedy Space Center Security Officer, Jack "Supr Jac" Hilderbrand talks on the phone at the security gate to Pad 39a just a day shy of his 70th birthday and the planned launch of the space shuttle Endeavour with the STS-127 crew. Hilderbrand has been working for the space program since 1960. Photo Credit: (NASA/Bill Ingalls)

Storm clouds approach Launch Pad 39A at NASA's Kennedy Space Center in Florida on Friday, July 10, 2009 as space shuttle Endeavour stands awaiting Saturday's planned launch of the STS-127 mission. Photo Credit: (NASA/Bill Ingalls)

Space shuttle Endeavour is in place at Launch Pad 39A, Friday, June 12, 2009 at NASA's Kennedy Space Center in Cape Canaveral, Florida. Endeavour is undergoing final preparations for its upcoming 16-day mission to the International Space Station. Photo Credit: (NASA/Bill Ingalls)

Space shuttle Endeavour is in place at Launch Pad 39A, Friday, June 12, 2009 at NASA's Kennedy Space Center in Cape Canaveral, Florida. Endeavour is undergoing final preparations for its upcoming 16-day mission to the International Space Station. Photo Credit (NASA/Bill Ingalls)

Space shuttle Endeavour is in place at Launch Pad 39A, Friday, June 12, 2009 at NASA's Kennedy Space Center in Cape Canaveral, Florida. Endeavour is undergoing final preparations for its upcoming 16-day mission to the International Space Station. Photo Credit (NASA/Bill Ingalls)