In Washington, just three days into this historic mission, the four astronauts were reported to be in high spirits. As they adjusted to the routines of space travel, they prepared for a brief engine firing designed to refine their lunar trajectory. Meanwhile, mission scientists on Earth were busy selecting the moon’s geological features to capture during the upcoming flyby.

The mission began in dramatic fashion when NASA’s Space Launch System (SLS) rocket, with the Orion spacecraft aboard, launched from Kennedy Space Center in Florida at 6:35 p.m. EDT on April 1. This marked the start of a planned 10-day test flight that will see the crew circumnavigate the moon before returning to Earth.

Leading the crew is Commander Reid Wiseman, accompanied by Pilot Victor Glover, Mission Specialist Christina Koch, and Canadian Space Agency astronaut Jeremy Hansen. Together, they represent the first group of astronauts to venture beyond Earth’s orbit since the Apollo missions concluded in 1972.

On Thursday, Orion’s main engine executed a critical five-minute-and-50-second burn, completing the translunar injection and propelling the crew out of Earth’s orbit towards their lunar destination. By Monday, Wiseman and his team are expected to reach the moon, continuing their groundbreaking exploration.

As of midmorning Friday, Wiseman and his crew were 100,000 miles from Earth and were quickly gaining on the moon with another 160,000 miles to go. They should reach their destination on Monday.

Later Friday, the crew was scheduled to fire Orion’s thrusters in the first outbound trajectory correction burn, set for 6:49 p.m. EDT. But NASA decided to cancel the correction burn because Orion’s trajectory is on the right flight path.

The mission has not been without its tense moments. A cabin leak alert earlier in the flight alarmed the crew, though flight director Judd Frieling said it turned out to be a false indication. “We quickly knew that there was no leak,” Frieling said at a briefing at Johnson Space Center. Hansen said the alarm definitely got the crew’s attention, as they briefly wondered whether they might have to cut the mission short.

Meanwhile, the lunar science team on the ground was assembling a targeting plan for Monday’s flyby, selecting geologic features on the moon’s surface that will be visible as Orion loops around it. The plan will focus on features that can help scientists understand how the moon and solar system formed, including craters, ancient lava flows, and ridges and cracks created as the moon’s outer layer shifted over billions of years.

During the roughly six-hour lunar science observation window, the sun, moon and spacecraft will be aligned so the crew can view about 20% of the moon’s far side — the hemisphere never visible from Earth — lit by the sun. Features expected to come into view include the full Orientale basin, Pierazzo crater and Ohm crater, none of which have ever been seen by the unaided human eye.

The mission is also expected to break Apollo 13’s human spaceflight record for distance from Earth. NASA’s updated estimate has the Artemis II crew reaching approximately 252,021 statute miles from Earth — surpassing the 1970 record by more than 3,000 miles.

During the flyby, the crew will also witness a solar eclipse lasting nearly an hour, during which the sun will be hidden behind the moon from Orion’s perspective.

Following a successful lunar flyby, the crew is set to return to Earth and splash down in the Pacific Ocean off the coast of San Diego. The mission’s 10th and final day is scheduled for April 10.

The Associated Press contributed to this report.