Thomas Marshburn

As an astronaut, when you're getting ready to go out of that hatch, you know that's the pinnacle of both your career and your life. The view completely blows you away. The real challenge is getting past the excitement and getting focused and down to work.

We have to be plumbers, electricians, construction engineers, or workers, on the space station, but at the same time running a laboratory, being scientists, being the best laboratory assistants we can be. It's all in a bundle; it's very exciting, it's a lot of fun.

When we're on the space station, we orbit the Earth 16 times per day, which means we're constantly moving to and away from the sun. From light to shadow, the temperature swings by 300 degrees. Of course we're protected by the gear we wear, but you can definitely feel this temperature change.