CAPE CANAVERAL, Fla. - In the Operations and Checkout Building at NASA's Kennedy Space Center in Florida, STS-131 Mission Specialist Rick Mastracchio verifies that his helmet is functioning properly. The members of space shuttle Discovery's STS-131 crew put on their launch-and-entry suits before heading to the Astrovan for the ride to Launch Pad 39A. The crew is participating in the Terminal Countdown Demonstration Test, or TCDT, a dress rehearsal for launch. TCDT includes training on the emergency egress systems at the launch pad, driving practice of the M-113 armored personnel carrier and a simulated launch countdown. The crew will deliver the multi-purpose logistics module Leonard, filled with resupply stowage platforms and science racks, to the International Space Station. STS-131, targeted for launch on April 5, will be the 33rd shuttle mission to the station and the 131st shuttle mission overall. For information on the STS-131 mission and crew, visit http:__www.nasa.gov_mission_pages_shuttle_shuttlemissions_sts131_index.htm. Photo credit: NASA_Kim Shiflett