The Artemis II moon mission will see four astronauts go on a 685,000-mile, 10-day journey around the moon. Here is what the timeline looks like:

Day 1 is launch day. The astronauts lift off aboard NASA's newest spacecraft, Orion, which will sit atop the Space Launch System rocket. The spacecraft will reach initial orbit and then high-Earth orbit to make a push toward the moon.

Days 2 through 4 are transit days, with the journey to the moon taking three days. Over the course of the journey, the crew will continue to evaluate Orion's systems and practice emergency procedures, in addition to other activities.

On day 5, Orion will enter the lunar sphere of influence, meaning the moon is the main gravitational pull. On day 6, the crew will come its closest to the moon while traveling the farthest from Earth, according NASA.

Days 7 through 10 will see the astronauts make their way back to Earth before re-entering Earth’s atmosphere at high speed, up to 25,000 miles per hour.

The Orion spacecraft will deploy a series of parachutes once through the heat of re-entry to slow down and it will splash down in the Pacific Ocean The U.S. Navy will recover the capsule.

-ABC News’ Mary Kekatos

#Who are the Artemis astronauts?

Three Americans and one Canadian will be aboard the Orion spacecraft -- named "Integrity" -- over the course of 10 days.

The team consists of Victor Glover, Christina Hammock Koch and Reid Wiseman of NASA and Jeremy Hansen of the Canadian Space Agency.

Wiseman is the commander of the Artemis II mission, Glover is the mission pilot, and Koch and Hansen are mission specialists.

Glover and Koch will also be the first person of color and first woman, respectively, to eventually step foot on the lunar surface in future Artemis missions.

-ABC News' Julia Jacobo

Artemis II took astronauts around the moon for the first time in more than 50 years. The four-person crew launched from NASA's Kennedy Space Center on Merritt Island, Florida, on April 1 for a 10-day journey, with the splashdown set for Friday off the California coast.

The history-making trip will pave the way for future Artemis missions intended to eventually see astronauts set foot on the moon and the building of a permanent lunar base.

Read more here about what you need to know regarding the Artemis II mission, including who the astronauts are and how to watch.

NASA's Artemis II mission is scheduled to launch today between 6:24 p.m. ET and 8:24 p.m. ET from Florida's Kennedy Space Center Launch Complex 39B.

The crew of four astronauts – mission commander Reid Weisman, mission pilot Victor J. Glover Jr., and mission specialists Christina Koch and Jeremy Hansen – will board the Orion crew capsule, dubbed Integrity, atop the SLS (Space Launch System) rocket for a more than 600,000-mile, 10-day journey around the moon to test critical spacecraft systems ahead of the Artemis IV mission, which is intended to land astronauts near the moon's South Pole, a region never explored by humans, in 2028.

At mission's end, Orion will splash down in the Pacific Ocean, off the coast of San Diego, with recovery operations conducted by the U.S. Navy and NASA.

The Artemis II mission crew awoke Monday to a message from former astronaut Jim Lovell. Though perhaps best known as the commander of Apollo 13, Lovell also was the command module pilot of Apollo 8, which in December 1968 became the first crewed spaceflight to reach and orbit the moon.

"Welcome to my old neighborhood," Lovell begins the message. "When Frank Borman and Bill Anders and I orbited the moon on Apollo 8, we got humanity's first up-close look of the moon and got a view of the home planet that inspired and united people around the world."

"I'm proud to pass that torch on to you as you swing around the moon and lay the groundwork" for future missions, Lovell said.

"It's a historic day, and how busy you'll be. But don't forget to enjoy the view," the message concludes. "Good luck and Godspeed from all of us here on the good Earth."

Apollo 8, which launched Dec. 21, 1968, famously took the historic photograph of the first Earthrise over the lunar surface as seen by humans.

Lovell recorded his message to the Artemis II crew shortly before his death on Aug. 7, 2025, at age 97.