Pallab Ghosh
Science correspondent

Right on schedule, Orion has reappeared from behind the Moon and checked back in with Earth.

First came the reassuring return of the radio signal on engineers' monitors, then a burst of data, and finally a clear voice from the capsule. The words were unremarkable - the relief in Mission Control was not.

"Houston, Integrity, comm check," mission specialist Christina Koch said as she broke the silence from Orion.

"It is so great to hear from Earth again."

During the 40 minutes of radio silence, the spacecraft had to look after itself.

Its onboard computers carried out a key engine burn on the far side – unseen and unheard from Earth – to bend Orion onto its return arc.

In human spaceflight there is always a tiny edge of uncertainty until you hear the crew again.

Families watching from the viewing gallery have spent the blackout poring over briefing notes, trying not to watch the clock.

Now that contact is restored, the data backlog will pour in.

Stored telemetry and images from the far side will be relayed through NASA’s Deep Space Network, ready for engineers and scientists to comb through in the coming days.

Early thumbnails hint at some of the most detailed views yet of the Moon’s hidden hemisphere.

For the crew, there is little time to savour the moment.

Rebecca Morelle
Science editor

We’ve been chatting to Nasa's science team and asking them what they're most looking forward to from the fly-by.

While they're definitely very excited to see the images the astronauts take, it's actually the audio that they really can't wait to hear.

As the astronauts fly around the far side of the Moon and train their eyes on the lunar landscape, they'll be saying what they see out loud and recording it into their tablets.

And these descriptions will be beamed back to Earth, so you can listen along at home.

"I just can't wait to hear how excited they are when they're actually looking at the Moon from close up," Dr Nicola Fox, Nasa’s Head of Science tells the BBC.

"So that's going to be the moment that's going to make me probably burst into tears."

Pallab Ghosh
Science correspondent

Scientists say this close pass will let Orion’s crew study the Moon as if they were doing a low‑altitude aerial survey, without ever touching down.

As they skim some 9,000 kilometres above the surface, the astronauts will be asked to "read the rocks" – picking out craters, cliffs and frozen lava flows, then photographing them in ultra‑high detail.

Those images, plus laser and camera data from Orion itself, should sharpen maps of the lunar surface and help geologists piece together how the Moon's crust was built and battered over billions of years.

Researchers are especially keen on views of the polar regions, where later missions hope to land near suspected deposits of water ice.

By watching how sunlight and shadow play across those pitted landscapes in real time, the crew can give planners a much better feel for which slopes look treacherous, which flat plains might take a lander, and where future astronauts should go hunting for resources.

Scientists will also be watching for any telltale glow from "lofted lunar dust", kicked up by sunlight and electrostatic forces, to understand how gritty particles move above the Moon’s surface.

Rebecca Morelle
Science editor

Image source, NASA

This is the last view from the Artemis II spacecraft, seen on the left of the photo, in the moments before connection was lost with the Earth - the small crescent on the right.

That silence is expected to last 40 minutes.

Throughout their epic journey, the astronauts' contact with mission control has been a constant link with home.

But now that link is lost, as the signal from the spacecraft is blocked by the Moon itself.

The 40 minutes without contact will be tense here at mission control. But for the four astronauts - so very far away from home - it will be just them and the Moon.

Pallab Ghosh
Science correspondent

Orion should be at its closest pass to the Moon – a sweeping fly-by that brought the spacecraft to within a few thousand miles of the surface. At that distance, the Moon fills the screen, with craters and mountain chains sliding past in slow, stately motion.

As well as taking vital scientific imagery, this part of the mission is also about grabbing gravity and using its force to hurl the astronauts back home, as if using the Moon like a slingshot.

The crew will be busy. Their cameras will be picking out features that lunar geologists back on Earth are desperate to scrutinise – fresh craters, ancient lava plains and scarps where the Moon’s crust has buckled.

The crew has also been asked to make quick pencil sketches and voice notes, capturing details that even the sharpest images can miss. It’s the kind of observational work that is normally done by astronomers on a mountaintop observatory.

Tonight, it is happening from a capsule sweeping round another world.

Pallab Ghosh
Science correspondent

Pilot Victor Glover's message just before loss of signal has echoes of the reading from the Book of Genesis from the Apollo 8 crew on Christmas Eve in 1968.

"In the beginning God created the heaven and the Earth. And the Earth was without form, and void; and darkness was upon the face of the deep."

Words that were all the more profound for those able to watch on TV, seeing live black-and-white images of the Moon and of the distant Earth as seen from their spacecraft

Command module pilot James (Jim) Lovell then took up the next verse followed by the commander, Frank Borman who signed off, with another iconic moment.

"And from the crew of Apollo 8, we close with good night, good luck, a Merry Christmas – and God bless all of you, all of you on the good Earth," followed by a crackle and long bleep, to punctuate this historic moment in human history.

Canadian astronaut Jeremy Hansen sent a message to family members in the Nasa viewing gallery, including his wife Catherine and his son Devon.

"I just wanted to let them know how much fun we're having out here," he says.

"It's extraordinary to be on the far side of the moon right now. Just see it hanging out there looking back at the Earth.

"Just wanted to say hi to all you guys, love you guys and we'll be heading back your way shortly."

Pallab Ghosh
Science correspondent

Orion has just slipped behind the bulk of the Moon and out of radio contact with Earth.

Engineers have always known this moment was coming – part of the flight plan – but when the signal drops, it's still a tense moment.

Right now, four astronauts are arcing round the far side of the Moon, further from home and more cut off than any humans have been for more than 50 years. There will be no comforting murmur for them from Mission Control, just the faint hum of fans and electronics as Orion follows its pre‑programmed path.

Outside the window, they are seeing landscapes we have only ever mapped with robots – steep‑walled craters, mountains thrown up by ancient impacts, and highlands pummelled by billions of years of debris.

For the next several minutes or so there is nothing anyone on Earth can do but wait. The spacecraft’s computers will handle the crucial engine burn that bends Orion onto its long loop home.

If everything goes to plan, the first sign that all is well will be a simple one: the signal returning followed by a cheery voice of one of the astronauts.

Houston begins speaking again and says it is a privilege to watch the astronauts.

Thank you to all of you for allowing us to be on this immense journey together pilot Victor Glover says.

"To all of you down there, we love you from the Moon," Glover speaks briefly about what he calls the most important mystery on earth "love".

Glover and the other astronauts will be out of communication for 40 minutes.

"Houston copies, we'll see you on the other side," Leah Cheshier Mustachio from NASA communications tells the astronauts.

Glover replies: "We will see you on the other side." Then there's just silence, as we all eagerly await to hear from the astronauts again.

Alison Francis
Senior science journalist

As the astronauts pass behind our celestial neighbour, the radio and laser signals that allow communication between the spacecraft and Earth, will be blocked by the Moon itself.

For about 40 minutes, the four astronauts will be totally alone.

They’ll spend the blackout dedicated to lunar observation – taking images, studying the Moon’s geology and simply gazing at its bleak beauty.

When they emerge and the signal is re-established, the world is expected to breathe a collective sigh of relief.

And the history-making astronauts will be able to share their incredible views with everyone back home.

Tara Mewawalla
Live reporter

When the crew woke up today, they listened to a special message recorded by Apollo 13 Commander Jim Lovell shortly before his death last year. "I'm proud to pass [this] torch on to you," he told them.

The Integrity spacecraft had already entered the lunar sphere of influence, meaning the pull of the Moon's gravity is stronger than that of the Earth.

The Artemis II astronauts set a new record for the furthest distance humans have ever travelled away from the Earth.

The record was previously held by the Apollo 13 crew, who travelled 248,655 miles from Earth in 1970. Artemis II will beat this record by about 4,102 miles, reaching a maximum distance of 252,757 miles at around 18:07 central time (22:07 GMT).

The crew named one of the Moon's craters after Commander Reid Wiseman's late wife Carroll, who died of cancer in 2020. They name another crater Integrity - after the Orion spacecraft which has carried them to the far side of the Moon.

The lunar observation period has begun and will last for around seven hours. Wiseman described his view of the earth as a "small crescent", while mission specialist Christina Koch told mission control she had an "overwhelming sense of being moved by the Moon".

In the coming hours, mission control is expecting Artemis II to temporarily lose communication with the crew as the Orion spacecraft passes behind the Moon.

Artemis II pilot and Nasa astronaut Victor Glover hears that his family is in the viewing gallery, listening to him give his "sit-rep" (situational report) to mission control.

When he is told Dionna Glover, his wife, is "all smiles", he replies: "Hey babe, I love you from the Moon... I'm glad you get to be there."

Mission specialist Christina Koch describes to mission control her lunar observation as an "incredible experience".

"At one point... I just had an overwhelming sense of being moved by looking at the Moon", she says.

She says this lasted "just a second or two" as something "drew me in suddenly into the landscape and it became real".

"The moon really is its own body in the Universe. It's not just a poster in the sky that goes by. It is a real place and when we have that perspective and we compare it to our home of the Earth it just reminds us how much we have in common.

"Everything we need the Earth provides and that is in and of itself truly a miracle."

Alison Francis
Senior science journalist

As we've just been reporting, the astronauts have been describing the colours they can see on the surface of the Moon.

The astronaut Harrison Schmitt was chosen for Apollo 17 because of his background as a geologist.

As he and Gene Cernan were collecting rock samples from the grey and bleakly beautiful lunar surface they were in for a surprise.

Schmitt suddenly said: “Hey wait a minute - it’s orange… there is orange soil… it’s all over.” A sample was brought back to Earth, and scientists think it’s microscopic glass beads that formed from lava "fire fountains" that rapidly cooled in the lunar vacuum.

The Artemis astronauts have a key objective to look for those nuances of colour on the surface of the Moon from the Orion spacecraft.

The eye of a well-trained person is one of the best scientific instruments for detecting those colours, as well as texture and geological features on the far side of the Moon.

Kelsey Young, Lunar Science Lead, told us: “When you really start to spend time and let your eyes get attuned to what you're seeing, you do see subtle shades of colour pop out, especially when you're close to the Moon, like our Artemis II astronauts will be.”

One of the astronauts tells mission control it's "truly awesome" the crew "now have the Moon and the Earth in window three simultaneously".

They say the Moon is a gibbous - when the illuminated part is greater than a semicircle and less than a circle - and the Earth is a crescent - the curved sickle shape.

"I'm guessing in about 45 minutes we'll have two identical crescents as we change our position in the universe," he adds.

Image source, NASA

In a "sit-rep" (situational report), astronaut Jeremy Hansen describes what it's like looking at the Moon.

"My eyes just now readjusted - the Moon is so bright when you come back to the window. I was in the interior of the cabin, I've come back to [the] window now."

He describes the colours he can see on the Moon's surface - including the darker and lighter greys that we are used to seeing.

He adds: "Right now, Aristarchus (a crater)... is hard for me to see from this window but that had greenish hues to me. It was very unique, I didn't see anything else like that anywhere else on this side of the Moon.

"And then I saw a lot of what i would call brownish hues."

The Artemis II crew are now calling down to mission control describing their observations of the Moon.

Astronaut Jeremy Hansen is speaking now - you can watch live at the top of the page.

Rebecca Morelle
Science editor

Image source, EPA

The Moon was born from the Earth.

About 4.5bn years ago, a huge Mars-sized body smashed into our planet, blasting off debris that then coalesced to form our celestial neighbour.

This means the Moon’s history is also our own - but this ancient archive is much better preserved in the lunar rocks.

With no plate tectonics, wind and rain, and oceans and vegetation to wipe this archive away, the Moon is a perfect time capsule.

Scientists are eagerly awaiting the images and observations that will be beamed back, but they’re even more excited about a future lunar landing, when rocks can be collected and brought home to their labs.

• Read more: First stop, the Moon. Next stop, Mars? Why Nasa's mission matters

Image source, NASA

The crew of the Artemis II mission have been sharing photographs of the Moon taken from on board the spacecraft.

Nasa says the below picture shows part of the far side of the moon.

The near side - the hemisphere we see from Earth - is visible on the right-hand-side in the photograph and is "identifiable by the dark splotches that cover its surface", Nasa says.

It adds: "These are ancient lava flows from a time early in the Moon’s history when it was volcanically active.

"The large crater west of the lava flows is Orientale basin, a nearly 600-mile-wide crater that straddles the Moon’s near and far sides. Orientale's left half is not visible from Earth, but in this image we have a full view of the crater.

"Everything to the left of the crater is the far side, the hemisphere we don’t get to see from Earth,"

Image source, NASA

Kevin Church
Videographer, BBC News

Image source, NASA

The astronauts have just been talking to mission control about photographs they are taking of the Moon - BBC videographer Kevin Church gives a run down of the camera kit they have at their disposal.

Compared to their Apollo predecessors, the Artemis crew have an array of digital cameras at their disposal.

They’ve brought three Nikon cameras: two D5s, one with a 14-24mm wide lens to capture the whole Moon and the other with an 80-400mm zoom lens that can pick out the finer details. They’ve also packed a Z9 with a 35mm lens, which takes images that are close to what the human eye can see.

There are GoPros mounted to the solar panels outside the spacecraft and each crew member has an iPhone to document the mission inside.

During the fly-by, the capsule’s lights will be dimmed to get the best possible pictures. However even these modern cameras will struggle to match the quality of the 70mm Hasselblad cameras used by the Apollo astronauts.

But packing one of these would mean bringing along multiple rolls of film, while a digital camera can store thousands of photos on a memory card the size of a postage stamp.