Three astronauts are due to return to Earth from the International Space Station (ISS), one month after a rocket failure delayed an earlier attempt.
The trio handed control of the ISS over to Russian cosmonaut Gennady Padalka, after more than 200 days in space.
Among them is Samantha Cristoforetti, who has set the record for most time in space on a single mission by a woman.
Their Soyuz spacecraft is due to undock from the ISS at 11:20 BST and land in Kazakhstan more than three hours later.
The commander of Expedition 43, Terry Virts, and his crewmates Anton Shkaplerov and Ms Cristoforetti have spent almost seven months on board the ISS carrying out scientific research and technology demonstrations.
According to a Nasa press release, they have travelled more than 84 million miles since their launch into space on 24 November.
They were originally due to leave a month ago, but their departure was delayed after the failure of a supply spaceship. The out-of-control unmanned Progress M-27M burnt up as it re-entered the Earth’s atmosphere.
The delay meant that on 6 June Samantha Cristoforetti set a new world record for most time spent in space by a woman on a single mission after clocking up more than 194 days.
She also famously introduced an espresso machine, which was specially adapted to work in space.
The hatch of the Soyuz spacecraft carrying the trio back to Earth closed at 08:04 BST.
Expedition 44 formally begins when the Soyuz undocks. It will be led by Mr Padalka, alongside fellow crew members US astronaut Scott Kelly and Russian cosmonaut Mikhail Kornienko.
Mr Kelly and Mr Kornienko are two-and-a-half months into a year-long tour of duty on the ISS, the longest continuous stay anyone will have had on board the 400km-high (250 mile) orbiting platform.
Three more astronauts are due to join them in July.