What is an astronaut?

Astronaut refers to someone who has been selected and trained by an agency or a company to fly aboard a spacecraft. It is not an honorary title or a single specialty: crews bring together test pilots, engineers, doctors, geologists and physicists. Basic training lasts between one and two years and includes survival skills, robotics, Russian, systems maintenance and hundreds of hours of pool diving to rehearse spacewalks.

The selection processes are extremely competitive. In the call that ESA closed in 2021, more than 22,500 valid applications were submitted, and only 17 people were selected in 2022: five career astronauts, eleven reserve astronauts and one candidate with a physical disability for a feasibility study. Years of training and waiting follow before assignment to an actual mission.

Being an astronaut means having flown, or training to fly, above a conventional boundary. The International Aeronautical Federation sets the edge of spaceflight at 100 km altitude, the so-called Kármán line; the United States has for decades used a lower threshold, 80 km, to recognize spaceflights. Between these two figures lie some famous suborbital flights, and with them, the debate over who deserves the label.

The word changes depending on the program: astronaut in the United States, Europe, Japan and Canada; cosmonaut in Russia; taikonaut in international usage for China. The job, however, is similar: operating the spacecraft, maintaining systems and carrying out other people's experiments. Suborbital tourism has added a new category of passengers who fly for a few minutes without years of training, which is why the US aeronautical authority stopped awarding its commercial astronaut wings and now simply publishes the list of those who have passed 80 km.