A NASA astronaut is a highly trained individual selected to participate in space missions conducted by the National Aeronautics and Space Administration (NASA). These astronauts undergo rigorous training in various fields, including science, engineering, and physical fitness, to prepare for the challenges of living and working in space. They may operate spacecraft, conduct experiments, and perform spacewalks. Astronauts can be classified into different roles, such as mission specialists, pilot astronauts, and payload specialists. Each role has specific responsibilities during a mission. NASA astronauts often collaborate with international space agencies and contribute to scientific research that benefits life on Earth and advances our understanding of the universe.