The US space agency’s Orion capsule is heading home.
The vehicle conducted a big engine burn on Monday in the vicinity of the Moon that now commits it to a splashdown in the Pacific Ocean on Sunday.
It was the last major powered maneuver for the next-generation crew ship on what has been, so far, a highly successful demonstration flight.
A trouble-free return at the weekend will see astronauts climb aboard Orion for its next mission in late 2024.
Nasa is planning a series of ever more complex outings for the capsule and its launch rocket – as part of its Artemis program.
This first flight, Artemis-1, has been all about testing systems in the absence of astronauts. They will get their opportunity on the next mission, Artemis-2.
But the whole plan depends on the current venture ending without incident.
Orion set off from the Kennedy Space Center in Florida on 16 November. It was put into an extended loop around the Moon that saw it reach some 430,000km (270,000 miles) beyond Earth – the furthest any spacecraft designed to carry humans has traveled.
Two big engine firings from Orion’s European Space Agency-provided propulsion unit – the first occurring last Thursday, and the second in the past few hours – have since turned the ship for home.
Nasa is describing the return as its “priority one” for the mission. Engineers want to see proof that the vehicle can survive the heat of re-entry into Earth’s atmosphere.