The Artemis II mission is now less than a day away from entering the pivotal lunar flyby part of the journey.

After days of travel, NASA leaders provided an update on Artemis II’s progress, along with new insight into what astronauts will be observing on the moon and beyond during Monday’s lunar flyby.

According to NASA flight director Rick Henfling, Orion is on an exceptionally precise trajectory toward the moon, which led to the cancellation of its first two planned course-correction burns.

“We found that Orion was on such a pinpoint trajectory that we didn't need to do the first two correction maneuvers,” Henfling said during Sunday’s news conference.

A third adjustment is still scheduled for Sunday at 11:03 p.m. ET. It is expected to be a brief, 14-second firing designed to keep the spacecraft perfectly aligned ahead of the flyby.

Just hours later, around 12:40 a.m. ET Monday, Orion will officially cross over into the lunar sphere of influence. This is the point where the moon’s gravity takes over from Earth’s. From there, the crew will begin a carefully choreographed sequence of observations as they pass by the lunar surface.

-ABC News' Briana Alvarado

Artemis II astronauts Reid Wiseman, Victor Glover Jr., Christina Koch and Jeremy Hansen are now donning their Orion Crew Survival System (OCSS) suits and beginning their operational demo.

The crew will practicing donning and removing the suits quickly in the event of a depressurization emergency within the spacecraft.

The demo affords an opportunity to see the Artemis II crew wearing their spacesuits as they travel ever closer to the moon ahead of Monday's lunar flyby.

-ABC News' Briana Alvarado

The Artemis II mission officially entered its fifth and final day before the highly anticipated lunar flyby as the crew awoke Sunday to the CeeLo Green song "Work."

The astronauts also heard from Apollo 16 astronaut Charlie Duke, who once landed on the moon on a different kind of Orion — a lunar module bearing the same name.

"I'm glad to see a different kind of Orion helping return humans to the moon as America charts the course to the lunar surface," Duke said in his message to the four-person crew.

"Below you, on the moon, is a photo of my family. I pray it reminds you that we in America and all of the world are cheering you on," Duke added. "Thanks to you and the whole team on the ground for building on our Apollo legacy with Artemis. Godspeed and safe travels home."

With the moon flyby just a day away, Sunday marks the final stretch of preparations before the big moment.

On Saturday, the crew received their full list of lunar targets, which includes 30 specific sites they’ll observe as they pass by the moon. During the observation period, the crew will go through a total of five shifts during what NASA is calling the lunar flyby sequence.

For the crew, the first four of those shifts are all about observing the lunar surface. This is when the windows will be pointing right at the moon. The astronauts will capture everything using their cameras and personal computers onboard the Orion crew module.

-ABC News' Briana Alvarado

Overnight, the Artemis II crew wrapped up a busy stretch of work in deep space, including a hands-on test of Orion's controls and more prep for Monday's lunar flyby.

According to NASA, the crew began a manual piloting demonstration at 9:09 p.m. ET, with mission specialists Christina Koch and Jeremy Hansen taking turns flying the spacecraft.

For about 41 minutes, they tested how Orion responds in different thruster modes to see how it handles both full, free movement and more limited steering. The goal is to give engineers a better sense of how the spacecraft performs when astronauts are actively flying it, NASA said.

NASA said the test is part of a series of evaluations, with commander Reid Wiseman and pilot Victor Glover expected to run a similar demonstration later in the mission -- on April 9 -- to give teams on the ground more data from different pilots.

Earlier in the day, the crew also spent time going over their plan for the lunar flyby. According to NASA, they reviewed a list of specific features on the moon's surface that scientists want them to photograph and describe.

That work will come into play on Monday, when Orion begins its flyby at 2:45 p.m. ET.

All of this is setting the stage for one of the most anticipated parts of the mission: when astronauts will see the moon up close and help document it in real time for scientists back on Earth.

The crew shared a new photo of the moon during day 4 of their mission, capturing parts of the lunar far side including Orientale basin peeking through from the right side of the lunar disk.

"This mission marks the first time the entire basin has been seen with human eyes," NASA said in an Instagram post.

-ABC News' Briana Alvarado

Orion's crew module has separated from the European Service Module, exposing the heat shield that will protect the spacecraft during its high-speed travel through the Earth's atmosphere.

That shield will withstand temperatures of up to 5,000 degrees Fahrenheit during the high-speed entry.