Scott Altman fits his helmet to his suit before heading for Launch Pad 39A at NASA's Kennedy Space Center.

STS-125 Commander Scott Altman fits his helmet to his launch-and-entry suit before heading for Launch Pad 39A at NASA's Kennedy Space Center in Florida. This launch will be Altman's fourth space shuttle flight. Liftoff is scheduled for 2:01 p.m. May 11 EDT. Atlantis' 11-day flight will include five spacewalks to refurbish and upgrade NASA's Hubble Space Telescope with state-of-the-art science instruments that will expand Hubble's capabilities and extend its operational lifespan through at least 2014. The payload includes a Wide Field Camera 3, fine guidance sensor and the Cosmic Origins Spectrograph. Photo credit: NASA/Kim Shiflett