From left: ESA astronaut Alexander Gerst, Roscosmos commander Maxim Suarev, NASA astronauts Reid Wiseman and Terry Virts, Roscosmos cosmonaut Anton Shkaplerov and ESA astronaut Samantha Cristoforetti.
The three Expedition 40/41 astronauts (left) with their backup crew after the last press conference before their launch on 28 May.
Alexander, Maxim and Reid will be launched to the International Space Station at 19:56 GMT (21:56 CEST), arriving planned a mere five hours later: 02:14 GMT (04:14 CEST).
The backup crew will watch their colleagues ascend from the Baikonur cosmodrome in Kazakhstan. From then on Terry, Anton and Samantha will focus on their own Expedition 42/43.
Watch the launch live from 19:00 GMT (21:00 CEST) as 274 tonnes of rocket propellants are consumed to accelerate the three astronauts to 28 800 km/h.