ISS023-E-020621 (7 April 2010) --- Astronaut Alan Poindexter, STS-131 mission commander who has led the Discovery crew on its mission to the International Space Station, displays a pleasant countenance as the hatches come open and two crews begin their traditional handshakes aboard the orbital outpost. Behind Poindexter is Japan Aerospace Exploration Agency astronaut Naoko Yamazaki, mission specialist.