NASA readies for crucial rehearsal ahead of its upcoming moon launch

As NASA makes final preparations to send four astronauts on a journey around the moon, a critical test Monday will reveal whether its enormous moon rocket is truly ready to fly.

Known as a “wet dress rehearsal,” the test is essentially an elaborate launch day walkthrough. NASA will fully fuel its next-generation Space Launch System rocket, going through each step as it would on the actual day up until roughly 30 seconds before liftoff.

The results will allow engineers and mission managers to assess the performance and readiness of the booster.

The much anticipated Artemis II mission is scheduled to launch no earlier than Sunday and send four astronauts on a 10-day journey around the moon. The path will take the crew farther from Earth than any humans have gone before.

But the official launch date is highly contingent on the outcome of the wet dress rehearsal.

“We’ll take some time after wet dress, we’ll review the data, and and then we’ll set up for our launch attempt,” Artemis launch director Charlie Blackwell-Thompson said in a news briefing last month.

If all goes well, NASA could announce a targeted liftoff in the coming days. If issues crop up, however, the space agency may be forced to delay the mission.

Engineers and mission managers will count down to a simulated launch time of 9 p.m. ET Monday. In the hours before, more than 700,000 gallons of cryogenic propellant will be loaded into the rocket.

As part of the practice run, mission managers will hold and resume the countdown several times in the final 10 minutes. These stops and starts help engineers evaluate the health of the rocket, including the automatic systems that are designed to kick in and take over control of the booster roughly 30 seconds before liftoff.

Artemis II will be the second trip to space for NASA’s Space Launch System rocket and Orion capsule. But it will be the first time they carry humans, making the mission a crucial step toward realizing NASA’s goal of returning astronauts to the lunar surface.

The Artemis II crew — NASA astronauts Reid Wiseman, Christina Koch and Victor Glover and Canadian astronaut Jeremy Hansen — have spent the last week and half in quarantine at NASA’s Johnson Space Center in Houston to keep them healthy ahead of the mission.

NASA rolled the Space Launch System rocket, topped with the Orion capsule, out to the launchpad at the Kennedy Space Center in Florida on Jan. 17. The agency had originally planned to conduct the wet dress rehearsal Saturday but pushed the timing back to wait out uncharacteristically frigid weather. A weekend cold snap sent temperatures plunging across the Southeast and up through the mid-Atlantic.

As such, NASA ruled out the first two launch opportunities (Friday and Saturday) in this month’s window, which extends through Feb. 11. The space agency has said there are possible launch windows in March and April, if needed.

To keep the launch on track for this month, the wet dress rehearsal likely needs to go off without a hitch.

If the test uncovers issues that require additional work, however, NASA may need to roll the rocket back to its Vehicle Assembly Building. The uncrewed Artemis I flight around the moon in 2022 was delayed six months because of hydrogen leaks identified during its first wet dress rehearsal.

This article was originally published on NBCNews.com