Expedition 24 crew members Tracy Caldwell and Doug Wheelock during ISS EVA 1 91027 training

JSC2009-E-226238 (28 Oct. 2009) --- Attired in training versions of their Extravehicular Mobility Unit (EMU) spacesuits, astronauts Tracy Caldwell, Expedition 23/24 flight engineer; and Doug Wheelock (mostly obscured), Expedition 24 flight engineer and Expedition 25 commander, are about to be submerged in the waters of the Neutral Buoyancy Laboratory (NBL) near NASA's Johnson Space Center. Divers are in the water to assist the crew members in their rehearsal, which is intended to help prepare them for work on the exterior of the International Space Station.