NASA said Friday it is now targeting February 2022 for the uncrewed lunar mission Artemis 1, the first step in America’s plan to return humans to the Moon later this decade. The space agency had initially wanted to launch the test flight by the end of this year, with astronauts on the ground by 2024 on Artemis 3, but the timeline has slipped back.

It achieved a major milestone Wednesday when it stacked the Orion crew capsule atop its Space Launch System megarocket, which now stands 322 feet (98 meters) tall inside the Vehicle Assembly Building at NASA Kennedy Space Center in Florida.

After further tests, it will be wheeled out to the launch pad for a final test known as the “wet dress rehearsal” in January, with the first window for launch opening in February, officials told reporters on a call.

“The February launch period opens on the 12th and our last opportunity in February is on the 27th,” said Mike Sarafin, Artemis 1 mission manager.

The next windows are in March and then April.

These potential launch periods are dependent on orbital mechanics and the relative position of the Earth with respect to its natural satellite.

The mission duration is expected to be four to six weeks.

It will also deploy a number of small satellites, known as CubeSats, to perform experiments and technology demonstrations.

Although likely to be pushed back, Artemis 2 is technically scheduled for 2023 and Artemis 3 for 2024, humanity’s return to the Moon for the first time since the Apollo 17 mission in 1972.

NASA says the moonwalkers will include the first woman and first person of colour to make the trip.

The space agency is seeking to establish a sustainable presence on the Moon, and use the lessons it learns to plan a crewed trip to Mars in the 2030s.