Space shuttle Atlantis foreground sits on Launch Pad A and Endeavour on Launch Pad B at NASA's Kennedy Space Center.

Space shuttle Atlantis (foreground) sits on Launch Pad A and Endeavour on Launch Pad B at NASA’s Kennedy Space Center in Florida. At the left of each shuttle are the open rotating service structures with the payload changeout rooms revealed. The rotating service structures provide protection for weather and access to the shuttle. For the first time since July 2001, two shuttles are on the launch pads at the same time at the center. Endeavour will stand by at pad B in the unlikely event that a rescue mission is necessary during space shuttle Atlantis’ upcoming mission to repair NASA’s Hubble Space Telescope, targeted to launch Oct. 10. After Endeavour is cleared from its duty as a rescue spacecraft, it will be moved to Launch Pad 39A for its STS-126 mission to the International Space Station. That flight is targeted for launch Nov. 12. Photo credit: NASA/Troy Cryder