The countdown has begun for the launch of NASA's Artemis II mission around the moon.
The 32-storey Space Launch System (SLS) rocket is set to blast off from the Kennedy Space Centre in Florida on Wednesday, sending four astronauts on a 10-day flight ending with a splashdown in the Pacific Ocean.
At a briefing by NASA on Monday, Emily Nelson, chief flight director, said teams in mission control and crew members are "ready to go".
Artemis II: Everything you need to know
The Artemis I mission didn't have any astronauts on board but was successfully sent into orbit around the moon in November 2022.
Artemis II takes it a step further with a crew on board, but it won't be until Artemis III that astronauts will actually land on the moon.
The US space agency hopes to use Artemis to build a base camp on the surface and potentially use it to get a human to Mars.
After a liquid hydrogen leak during a practice launch in February, NASA was forced to delay the operation until Wednesday.
At 98m tall, the SLS rocket is roughly the height of Parliament's Elizabeth Tower, which houses Big Ben. Not since Apollo 17 in 1972 have humans touched down on the moon's surface.
The astronauts on board are NASA's Reid Wiseman, Victor Glover and Christina Koch, plus Jeremy Hansen of the Canadian Space Agency.
Read more from Sky News:
NASA's lunar base ambitions
Can moon mission bring us together?
Why is NASA returning to the moon?
British astronaut Major Tim Peake has said Europe, including the UK, is heavily involved in the Artemis programme.
"We were there on Artemis I... we built the European service module which powers the Orion spacecraft that provides all the electrical power, the life support systems, the propellant," he said.
NASA has the first six days of April to launch Artemis II before standing down until the end of the month.
(c) Sky News 2026: Artemis II: Countdown begins to NASA's trip around the moon, the first manned m
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