Members of the crew can be seen in their orange spacesuits now while at the controls of the Orion spacecraft ahead of their reentry.

Here's a look at the "carefully timed sequence" of the final stages of Orion's descent, according to NASA. All times Eastern.

7:33 p.m.: Orion's crew module will separate from the European Service Module, exposing the heat shield that will protect the spacecraft as it travels through the Earth's atmosphere.

7:37 p.m.: Orion will perform an 18-second raise burn that fine-tunes the reentry angle of the spacecraft to minimize the time the heat shield will experience high temperatures.

7:53 p.m.: Orion will make first contact with the upper atmosphere, beginning a planned 6-minute communications blackout. The crew is expected to experience up to 3.9 Gs as the spacecraft travels nearly 35 times the speed of sound.

7:59 p.m.: NASA will regain communications with the crew.

8:03 p.m.: At around 22,000 feet in altitude, drogue parachutes will deploy to help slow the capsule ahead of splashdown.

8:04 p.m.: Three main parachutes will deploy at around 6,000 feet, reducing Orion's speed to less than 136 mph.

8:07 p.m.: Orion will splash down in the Pacific Ocean, off the coast of San Diego, having slowed to 20 mph.

The U.S. Geological Survey warned residents of Southern California that they should expect to hear a sonic boom from the Artemis II reentry in a few hours.

The sonic boom is expected between approximately 5-5:15 p.m. PT, it said.

It will take Orion about 14 minutes to travel the 400,000 feet from space to splashdown off the coast of San Diego.

Everyone inside the spacecraft will be laser-focused on monitoring the onboard systems during their descent through the atmosphere, according to retired NASA astronaut Barry "Butch" Wilmore.

The astronauts train for "all types of failures," so their mindset is just to concentrate on the jobs at hand, he said.

"You can't let apprehension involve you in those time frames," Wilmore told ABC News. "You have to focus on your task, whatever that might be, and you have to perform because if you don't, the consequences are pretty dire."

-ABC News' Briana Alvarado

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.