Le coin des amatheurs de sciences version 2
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There are several types of ISS crews, and the organization changed with the years.
Until 2003
The permanent crews were the main ones : they stayed in the station to maintain it and to carry out scientist experiments. They generally stayed six months in orbit and were composed of three members : two Americans and a Russian or an American and two Russians (alternatively). They were carried by shuttles (Columbia, Discovery, Atlantis or Endeavour).
There were also the « taxi-crews ». A Soyuz is permanently attached to the station to permit the permanent crew to come back on Earth in case of problem. For safety, this ship was replaced roughly every six months. The taxi-crews were made to join the station with a new ship and leave it after a few days with the old one. They were composed of three persons (maximal capacity of Soyuz).
Finally, there are crews for deliveries : supply, new segments, material, ... This crews have a variable composition and can travel with Soyuz or a shuttle.
From 2003 to 2006
On February 1st, 2003 took place Columbia's accident. NASA cancelled all shuttle's flights. Then only Soyuz was available for orbital flights and the organization changed.
Taxi-crews have been suppressed : the changes of safe Soyuz were made with the changes of permanent crews. So the new permanent crew arrived in the station with a new Soyuz, that would serve him for safety, and the previous crew left the station with the old ship.
Moreover, the size of crews has to be reduced to two members, an American and a Russian. These changes concern the crew 7 to 12.
From 2006 to 2009
Because the return of Discovery on August 9, 2005 was succesful, shuttles are used again. It permitted to have permanent crews of three persons again (since 13th crew). However, the composition didn't become exclusively American and Russian, by giving access to European astronauts (a German one arrived on July 6, 2006).
Moreover, the idea of changing the Soyuz in the same time that the crew remained. Since this change, crews are changed in two steps. Two members are replaced by two persons coming with Soyuz ; the third crew member is replaced later, generally with a shuttle.
Since 2009
The return of shuttles also permitted to build the station again (Soyuz can't carry big segments), so in 2009 its capacity raised to 6 people. Then on May 29, three astronauts joined the 19th crew and they formed together the 20th crew. This event was also the occasion to have for the first time in the station an astronaut of each five partners of ISS (Canada, ESA, Japan, Russia, USA).
So here is the list of permanent crews, adapted from the site Astrocosmos and from NASA. The dates are indicated according to international schedule GMT. For each crew, the first indicated member is the commander. Click on a photograph to enlarge it