Expedition 51 backup crewmembers Sergey Ryazanskiy pose for pictures as part of pre-launch preparations.

In the Integration Building at the Baikonur Cosmodrome in Kazakhstan, Expedition 51 backup crewmembers Sergey Ryazanskiy of the Russian Federal Space Agency (Roscosmos, left) and Randy Bresnik of NASA (right) pose for pictures April 6 as part of pre-launch preparations. Ryazanskiy and Bresnik are serving as backups to the prime crew, Jack Fischer of NASA and Fyodor Yurchikhin of Roscosmos, who will launch April 20 on the Soyuz MS-04 spacecraft for a four and a half month mission on the International Space Station. NASA/Gagarin Cosmonaut Training Center/Andrey Shelepin