The BBC’s Science Editor Rebecca Morelle has spoken to the Artemis II crew ahead of their likely splashdown on Saturday.
As the astronauts pass behind the Moon they will experience a moment of silence and solitude as communication with the Earth is blocked.
Crew nears moon on historic flyby and sends back striking images of Earth.
The mission's last, big push on its lunar journey takes humans out of the Earth's orbit for the first time since 1972.