The crew of NASA’s Artemis II will make its closest approach to the moon Monday afternoon after launching from Kennedy Space Center last week.

It marks a critical milestone of the agency’s Orion space capsule, sending humans on a mission to the moon for the first time in more than 50 years. As the capsule loops around the moon, the astronauts will reach farther into space than humans have ever ventured.

The Orion spacecraft is now in the lunar sphere of influence, meaning the moon’s gravity has more pull on the vehicle than the Earth. At 1:46 p.m. ET, the crew will surpass the record for the farthest distance traveled from Earth by humans, which was set by the Apollo 13 mission at 248,655 statute miles from Earth. At 2:45 p.m., the crew will begin making observations of the surface of the moon during the flyby.

As the vehicle circles the far side of the moon, communication back to Earth is expected to be blocked for about 40 minutes. At 7:02 p.m., the crew is expected to have reached the mission’s maximum distance from Earth at 252,760 statute miles.

The flyby is scheduled to conclude at 9:20 p.m. and then the crew will be on its way home, with a planned splashdown in the Pacific Ocean off San Diego, Calif. on Friday at 8:07 p.m.

During the Artemis II flyby, the crew will pass over two previous human lunar landing sites — Apollo 12 and 14.

Lunar science observations

During the lunar flyby, the closest Orion will come to the surface of the moon is 4,070 miles. From that distance the crew will have a unique vantage point of the moon as a full disc — and the ability to take observations never before seen by human eyes.

NASA scientists have identified about 35 geological features for the crew to observe. Working in pairs, they will take photos of the sites and describe them in real time to scientists at Mission Control at the Johnson Space Center in Houston.

“They’re going to be absolutely buzzing,” said Artemis II lunar science lead Kelsey Young on Sunday. The team will be monitoring the observations and providing guidance to the crew.

“The science team will get to work right away, kind of synthesizing those [observations], and then we’ll actually downlink the rest of the descriptions overnight, in advance of a crew conference we’ll have the following morning to continue the science discussion.”

Artemis II has ten science objectives for the flyby. One is to observe color variations on the lunar surface. Changes in color can indicate the composition of the minerals on the surface. These changes are hard to detect with satellite images.

“This is something that human eyes are just incredibly good at teasing out nuances about,” said Young.

Satellites like the Lunar Reconnaissance Orbiter, which launched in 2009, have given scientists a better understanding of the lunar surface. The Artemis II crew’s observations will build on that knowledge.

“We understand, you know, what it’s made out of. We understand the topography, but we don’t know what the crew are going to see in these specific illumination conditions from a scientific perspective,” said Young. “And that’s exciting.”

NASA astronaut and Artemis II mission specialist Christina Koch peers out of one of the Orion spacecraft’s main cabin windows, looking back at Earth on Saturday, as the crew traveled towards the Moon.

NASA via Getty Images/Getty Images North America

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NASA via Getty Images/Getty Images North America

The observations will help future landing missions. One target site is a potential future landing area for an uncrewed payload mission. The crew will also get a small glimpse of the lunar south pole — where humans might land as early as 2028.

The mission so far

Artemis II is more than halfway through its slingshot mission around the moon and back. This is a test flight of the Orion space capsule, carrying a human crew for the first time.

“Our mission continues to go incredibly well,” said Lori Glaze, who leads NASA’s Artemis program.

Tests include manual control of the Orion spacecraft. Mission pilot Victor Glover practiced the maneuverability of the capsule for future rendezvous with lunar landing vehicles.

The crew tested the spacecraft’s life support systems, like the carbon dioxide scrubbers, and donned their space suits midflight — which future astronauts might have to do in an emergency.

The Artemis II mission is also testing the first deep-space toilet. NASA’s Universal Waste Management System is stowed in the floor of Orion and allows the crew to use the bathroom in private. So far, the hardware has had a few hiccups (not having enough water in the bowl and, at a different point, not being able to dump the waste overboard due to a frozen line), but those seem to be resolved.

“We’re continuing to proceed with the mission and the use of the toilet nominally,” said Artemis II flight director Rick Henfling, meaning the crew is allowed to use the onboard lavatory.