S69-31060 (18 April 1969) --- Suited astronaut Neil A. Armstrong, wearing an Extravehicular Mobility Unit (EMU), participates in lunar surface simulation training on April 18, 1969 in building 9, Manned Spacecraft Center (MSC). Armstrong is prime crew commander of the Apollo 11 lunar landing mission. Here, he is opening the Modularized Equipment Stowage Assembly ( MESA).