Astronauts Jeffrey A. Hoffman (far left) and F. Story Musgrave (second left) monitor a training session from consoles in the control room for the Neutral Buoyancy Simulator (NBS) at the Marshall Space Flight Center (MSFC). Seen underwater in the NBS on the big screen and the monitors at the consoles is astronaut Thomas D. Akers. The three mission specialists, along with astronaut Kathryn C. Thornton, are scheduled to be involved in a total of five sessions of extravehicular activity (EVA) to service the Hubble Space Telescope (HST) in orbit during the STS-61 mission, scheduled for December 1993.