"Since there always has to be a certain number of astronauts manning the station at all times, one of the main aspects of the mission was to transport a new team to the station and bring back some members of the previous team back to Earth"

This quote by Philippe Perrin talks to the importance of having a specific number of astronauts manning the International Space Station (ISS) at all times. This indicates that the mission of carrying a new group to the station and bringing back some members of the previous team back to Earth is an important part of the objective. This is needed to make sure that the ISS is constantly staffed with the needed workers to perform its operations. The astronauts that are sent out to the ISS are extremely trained and experienced professionals who can performing the required tasks to keep the station running. The mission of carrying new astronauts to the station and reviving a few of the previous group back to Earth is a crucial part of the objective and is needed to guarantee that the ISS is always staffed with the necessary personnel.