Butch and Yelena

NASA astronaut Barry 'Butch' Wilmore and Roscosmos cosmonaut Yelena Serova on the International Space Station doing refresher training.

Astronauts regularly refresh their skills during their six-month mission on the world's weightless research centre.

ESA astronaut Alexander Gerst took this picture during his six-month Blue Dot mission.

Follow Alexander and his mission via http://alexandergerst.esa.int