The NASA Astronaut Corps is a unit of the United States National Aeronautics and Space Administration (NASA) that selects, trains, and provides astronauts as crew members for U.S. and international space missions.

    The first U.S. astronaut candidates were selected by NASA in 1959, for its Project Mercury with the objective of orbiting astronauts around the Earth in single-man capsules. The military services were asked to provide a list of military test pilots who met specific qualifications. After stringent screening, NASA announced its selection of the "Mercury Seven" as its first astronauts. Since then, NASA has selected 20 more groups of astronauts, opening the corps to civilians, scientists, doctors, engineers, and school teachers. As of the 2009 Astronaut Class 61% of the astronauts selected by NASA have come from military service.[1]
    NASA selects candidates from a diverse pool of applicants with a wide variety of backgrounds. From the thousands of applications received, only a few are chosen for the intensive Astronaut Candidate training program. Including the “Original Seven”, 339 candidates have been selected to date