It is called “astronaut” in Europe and “cosmonaut” in Russia but these words mean the same thing. The job of astronaut is certainly the most dreaming of young people and many adults. It is also one of the riskiest trades in the world with that of submarine diver in extreme environment.
Because of these difficulties many astronauts are military pilots with a lot of experience, sometimes even test pilots.
The astronaut trade is open to all academics specializing in astronomy, applied physics, biology, medicine, and the amount of new science based on telecommunications and computing, to name only remote sensing.
Many astronauts are researchers in civil life who wrote to ESA or NASA to become an astronaut. After passing the entrance exams, they followed for a few years a physical training and advanced technical courses to know the astronautics and the mission that was going to be entrusted to them.
Then, in turn, they were lucky to be able to board a rocket or space shuttle to accomplish their mission. On their return some remain astronauts, others return to civilian life in their laboratory.