'Welcome home, Artemis': Crew celebrates historic 10-day moon mission

Despite all the preparation, safety systems and redundancies, the nature of human spaceflight is inherently risky, according to experts.

"I think it'd make everybody feel comfortable to say that all the risk was knocked down to zero," Danny Olivas, former NASA astronaut and engineer, told ABC News. "The truth is it is not and never will be."

NASA is using a variety of tools and systems to ensure crew safety from launch to splashdown, including customized lifesaving spacesuits, a launch abort system, radiation monitoring, an emergency egress system and other contingencies.

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-ABC News' Briana Alvarado

The Artemis II mission, set to lift off as early as Wednesday and fly around the moon, is the latest chapter in a long history of lunar exploratory space missions launched by NASA over the last six decades.

In the same way that Artemis II serves as the first crewed spaceflight to test technology for future missions to the moon and Mars, Apollo 8, which launched on Dec. 21, 1968, was the first crewed spaceflight to reach the moon and also served as a lunar landing preparation mission, preceding Apollo 11's July 20, 1969, lunar landing.

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-ABC News' Mason Leib

Weather is expected to be a green light at the Kennedy Space Center in Cape Canaveral, Florida, for the Artemis II mission to launch.

The two-hour window from 6:24 to 8:24 p.m. will feature temperatures in the mid to low 70s, forecasters say.

Winds will be between 8 and 16 mph, with a rare gust up to 20 mph, max.

There will be a mix of clouds and clear skies with no forecast chance for rain or lightning.

-ABC News’ Kenton Gewecke

As NASA engineers and astronauts prepare to launch the Artemis II rocket to the moon today, here are some key numbers regarding the mission.

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-ABC News' Julia Jacobo