Four astronauts have left the International Space Station a month early, in the first medical evacuation since the station was put into Earth's orbit in 1998.
The astronauts, known as Crew 11, are expected to splash down off the coast of California in the early hours of Thursday local time.
Their journey was cut short because of medical issue involving one crew member, Nasa said. The agency did not provide details about the crew member or the nature of the medical issue, but said they were in stable condition.
Control of the ISS has been handed over to Russian cosmonaut Sergey Kud-Sverchkov and two other crew members.
The astronauts, Mike Fincke and Zena Cardman, Japan's Kimiya Yui and cosmonaut Oleg Platonov, arrived on the ISS on 1 August expecting to complete a standard six and a half month stay. They were due to come home in mid-February.
