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The space station mission was kind of the culmination of all of my experience of being a NASA Astronaut, so it had brought all of my previous experience into play. I had to learn the Russian language to a fluent level so that I could function as the co-pilot of the Soyuz Spacecraft that we flew up and back from the space station. And then the challenge of being the Commander of the whole expedition, a six and a-half month flight aboard the international space station. I felt the burden of the whole mission on my shoulders, which was fine, and fortunately everything did go well.

Source: bigthink.com
The space station mission was kind of the culmination of all of my experience of being a NASA Astronaut, so it had brought all of my previous experience into play. I had to learn the Russian language to a fluent level