No-one will have been further from home than the Artemis astronauts.
But as the Earth shrinks ever smaller in their rear-view mirror, they’ve had a constant connection with mission control in Houston, Texas. The calm words from the Nasa team have given the crew a comforting link with home.
That link is about to be lost.
As the astronauts pass behind the Moon at about 23:47 BST (18:47 EDT) on Monday, the radio and laser signals that allow the back-and-forth communication between the spacecraft and Earth will be blocked by the Moon itself.
For about 40 minutes, the four astronauts will be alone, each with their own thoughts and feelings, travelling through the darkness of space. A profound moment of solitude and silence.
Artemis pilot Victor Glover told us he hopes the world will use the time to come together.
“When we’re behind the Moon, out of contact with everybody, let’s take that as an opportunity,” he told BBC News before the mission. “Let’s pray, hope, send your good thoughts and feelings that we get back in contact with the crew.”
More than 50 years ago, the Apollo astronauts also experienced the isolation brought by a loss of signal during their missions to the Moon.
Perhaps none more so than Apollo 11’s Michael Collins.
In 1969, while Neil Armstrong and Buzz Aldrin made history taking the first steps on the lunar surface, Collins was alone in the command module, orbiting the Moon.
As his craft passed behind the far side, contact with the pair on the lunar surface, as well as with mission control, vanished for 48 minutes.
He described the experience in his 1974 memoir Carrying the Fire, saying he felt “truly alone” and “isolated from any known life”, but that he did not feel fear or loneliness.
In later interviews, he described the peace and tranquillity brought by the radio silence, saying it offered a break from the constant requests from mission control.
More on Artemis II
Back on Earth, the blackout will be a tense time for those with the job of maintaining contact with the spacecraft.
At the Goonhilly Earth Station in Cornwall, in the south-west of England, a huge antenna has been collecting signals from the Orion capsule, carefully pinpointing its position throughout its journey, and feeding this information back to Nasa HQ.
Matt Cosby, Goonhilly’s chief technology officer, told the BBC: “This is the first time we’re tracking a spacecraft with humans on it.
“We’re going to get slightly nervous as it goes behind the Moon, and then we’ll be very excited when we see it again, because we know that they’re all safe.”
But the hope is these dropouts in communications could soon become a thing of the past. And Cosby says that will be essential as Nasa – and other space agencies around the world – begin to build a Moon base and ramp up further exploration.
“For a sustainable presence on the Moon, you need the full comms – you need the full 24 hours a day, even on the far side, because the far side will want to be explored as well,” he said.
Programmes like the European Space Agency’s Moonlight are planning to launch a network of satellites around the Moon to provide continuous and reliable communication coverage in the future.
For the Artemis astronauts, their time without contact with the Earth will allow them to devote all of their attention to the Moon.
They’ll spend the blackout dedicated to lunar observation – taking images, studying the Moon’s geology and simply gazing at its splendour.
When they emerge from the Moon’s shadow, and that signal is re-established, the world will breathe a collective sigh of relief.
And the history-making astronauts will be able to share their incredible views with everyone back home.
