Astronaut, designation, derived from the Greek words for “star” and “sailor,” commonly applied to an individual who has flown in outer space. More specifically, “astronaut” refers to those from the United States, Canada, Europe, and Japan who travel into space. Those Soviet and later Russian individuals who travel into space are known as cosmonauts (from the Greek words for “universe” and “sailor”). China designates its space travelers taikonauts (from the Chinese word for “space” and the Greek word for “sailor”).
Even though initially most U.S. astronauts were test pilots, this requirement had more to do with their ability to perform effectively in high-stress situations than with their piloting skills, since the spacecraft used in the Mercury, Gemini, and Apollo programs had limited maneuvering capability in orbit and came back to Earth using parachutes for reentry. Beginning in 1978, with the advent of the space shuttle, which functioned as a laboratory and operations centre when in orbit and then as a high-speed, difficult-to-control glider as it reentered the atmosphere and flew to a runway landing, the National Aeronautics and Space Administration (NASA) selected two types of individuals as astronaut candidates. One group was required to have extensive flying experience in jet aircraft. These astronaut candidates were trained to serve as shuttle pilots and eventually shuttle mission commanders. The second group was chosen to become mission specialist astronauts. These candidates were not required to be pilots (though some were); rather, they were individuals with advanced scientific, medical, or engineering training or experience. Beginning in 1992, in anticipation of participating in missions to the International Space Station (ISS), a number of individuals from various countries became international mission specialist astronaut candidates.
Mission specialists were trained to have primary responsibility during a mission for operating shuttle or space station systems and carrying out payload and experimental activities. Mission specialists also performed extravehicular activities (space walks).
Credit : Britannica
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