Astronauts Scott Parazynski and Chris Hadfield on mission STS-100

NASA Astronaut Scott E. Parazynski (centre) and Canadian Space Agency astronaut Chris A. Hadfield (partially obscured) prepare to unpack the new Space Station Remote Manipulator System (SSRMS) or Canadarm2 during the first of two mission STS-100 space walks on April 22, 2001. (Credit: NASA)