Usually, astronauts go into space in groups called a crew. ... The responsibilities range from being the commander, the one in charge of the crew and the safety of the spacecraft, to being a mission specialist trained in repairing the spacecraft or retrieving satellites.
An astronaut is a person trained, equipped, and deployed by a human spaceflight program to serve as a commander or crew member aboard a spacecraft. Although generally reserved for professional space travelers, the terms are sometimes applied to anyone who travels into space, including scientists, politicians, journalists and tourists.