This close-up of astronaut and mission specialist Kathryn Thornton readies herself for submersion into the water in the Marshall Space Flight Center (MSFC) Neutral Buoyancy Simulator (NBS) where she is participating in a training session for the STS-61 mission. The NBS provided the weightless environment encountered in space needed for testing and the practices of Extravehicular Activities (EVA). Launched on December 2, 1993 aboard the Space Shuttle Orbiter Endeavor, STS-61 was the first Hubble Space Telescope (HST) serving mission. During the 2nd EVA of the mission, Thornton, along with astronaut and mission specialist Thomas Akers, performed the task of replacing the solar arrays. The EVA lasted 6 hours and 35 minutes.