Stock Photo - Astronaut Stuart A. Roosa, backup crew command module pilot of the Apollo 17 lunar landing mission, participates in extravehicular activity simulation training under zero-gravity conditions aboard a U. S. Air Force KC-135 aircraft. A mock-up of the Scientific Instrument Module (SIM) bay of the Apollo 17 Service Module is used in the exercise. Here, Roosa simulates retrieving the film cassette of the Mapping Camera from the SIM bay. Astronaut Ronald E. Evans, Apollo 17 prime crew command module pilot, is scheduled to receive film cassettes from the Mapping Camera, Panoramic Camera, and Lunar Sounder during Apollo 17 trans-Earth extravehicular activity.