Four astronauts are hours away from strapping into a spacecraft and departing the International Space Station about a month early after one of them experienced a health issue. The impending departure would mark the first time in the station's 25-year history that a crew on the orbital outpost has cut a mission short in order to be medically evacuated.

Four astronauts who left the International Space Station a month early are about to splash down off the coast of California - watch live above

American astronauts Mike Fincke and Zena Cardman, Russian cosmonaut Oleg Platonov and Japanese astronaut Kimiya Yui were set to undock from the ISS at 11.05am NZT, after five months in space.