Astronaut training. Space shuttle astronauts Philippe Perrin and Franklin R. Chang-Diaz practising for construction of part of the International Space Station (ISS). They are training underwater to simulate the weightless (microgravity) conditions of orbit. This is training for mission STS-111, during which the Shuttle Endeavour docked with the ISS. The tasks the astronauts carried out included adding the Mobile Base System (part of the Canadarm2 robotic arm) and delivering supplies. Photographed in December 2001 at NASA's Neutral Buoyancy Laboratory, Johnson Space Center, Houston, Texas, USA.