NASA astronauts are highly trained U.S. citizens selected by NASA to pilot spacecraft, conduct spacewalks, perform scientific experiments, and support human space exploration missions.[1][4][9] Derived from Greek words meaning "star sailor," they undergo rigorous multi-year training at NASA's Johnson Space Center, including spacecraft systems, robotics, survival skills, medical procedures, and T-38 jet piloting, with requirements like a STEM master's degree, three years of professional experience, and strong leadership abilities.[1][4] They hold specialized roles such as commander, pilot, mission specialist, flight engineer, and science officer, essential for operating the International Space Station (ISS), deploying satellites, maintaining equipment, and researching topics like cancer and human physiology in microgravity.[2][3][4][7] On the ISS, orbiting 240 miles above Earth, crews of 3-6 astronauts work 16-hour days on experiments, maintenance, and two hours of daily exercise to counter muscle and bone loss, while remaining on call 24/7.[4][6][7] Key achievements include advancing the Apollo program's Moon landings, constructing the ISS, and preparing for Artemis missions to the lunar South Pole, where astronauts will explore uncharted areas and conduct novel experiments.[4][5] The corps, comprising civil servants and military detailees with diverse skillsets, also contributes to mission design, crew assignments, and technical leadership.[5] Currently, NASA astronauts operate on the ISS, integrating with international partners via Soyuz or SpaceX Dragon spacecraft, and train for deep-space goals amid evolving needs from test pilots to versatile scientists.[4][5][7] As of recent selections, candidates spend two years in basic training before full qualification, ensuring readiness for Artemis and beyond.[4] (298 words)