The four astronauts of NASA's Artemis II mission entered the moon's gravitational sphere of influence early Monday morning as they cruised along a path that will soon take them over the shadowed, lunar far side to become the farthest-flying humans in history.

The Artemis II crew, flying in their Orion capsule since launching from Florida last week, are due to awake around 10:50 a.m. ET Monday for their sixth flight day. By 7:05 p.m., they will reach the mission's maximum distance from Earth of roughly 252,757 miles, 4,102 miles beyond the record held by the Apollo 13 crew for 56 years.

As NASA astronauts Reid Wiseman, Victor Glover and Christina Koch and Canadian astronaut Jeremy Hansen approach the distance record, they will be sailing around the moon's far side, witnessing it from roughly 4,000 miles above its darkened surface as it eclipses a basketball-sized Earth in the distant background.

The milestone is a climactic point in the nearly 10-day Artemis II mission, the first crewed test flight of NASA's Artemis program. The multibillion-dollar series of missions aims to return astronauts to the moon's surface by 2028 before China and establish a long-term U.S. presence there over the next decade, building a moon base that would serve as a proving ground for potential future missions to Mars.

Officially starting at 2:34 p.m. ET, the lunar flyby will plunge the crew into darkness and brief communications blackouts as the moon blocks them from NASA's Deep Space Network, a global array of massive radio communications antennas the agency has been using to talk to the crew.

The flyby will last about six hours, during which the astronauts will use professional cameras to take detailed photos through Orion's window of the silhouetted moon, showing a rare and scientifically valuable vantage point of sunlight filtering around its edges in what will effectively be a lunar eclipse.

They will also have the chance to photograph a rare moment in which their home planet, dwarfed by their record-breaking distance in space, will rise from the lunar horizon as their capsule emerges from the other side, a celestial remix of a moonrise seen from Earth.

A team of dozens of lunar scientists positioned in the Science Evaluation Room at NASA's Johnson Space Center in Houston will be taking notes as the astronauts, who studied an array of lunar phenomena as part of mission training, describe their view in real time.

-Reporting by Joey Roulette; Editing by Don Durfee and Aurora Ellis/Reuters