CAPE CANAVERAL, United States (AFP) — The National Aeronautics and Space Administration (NASA) in the United States (US) began its two-day countdown Monday ahead of what is slated to be its first crewed moonshot in more than half a century, a long-anticipated loop around Earth’s satellite that is to pave the way for future exploration.

The first window to launch from the Kennedy Space Center in Florida opens Wednesday, April 1 at 6:24 pm (2224 GMT), and NASA officials said the countdown began at 4:44 pm.

“The vehicle is ready, the system is ready. The crew is ready,” Amit Kshatriya, the US space agency’s associate administrator, said in a briefing.

“Behind this flight stands a campaign,” he continued, noting recently announced plans including constructing a lunar base.

If Wednesday’s launch is cancelled or delayed for any reason, there are more liftoff opportunities through April 6.

As of Monday evening, NASA officials voiced confidence that engineering operations and final preparations were proceeding smoothly.

“We’ll fly when this hardware is ready,” launch director Charlie Blackwell-Thompson told journalists.

“But certainly all indications are right now we are in excellent, excellent shape.”

The four astronauts set to carry out the Moon voyage — Americans Reid Wiseman, Victor Glover and Christina Koch, along with Canadian colleague Jeremy Hansen — are in quarantine ahead of their journey.

NASA officials said Monday evening that they would have the opportunity to have dinner with their families at a Florida beach house.

– Cloudy with a chance of history –

The odyssey will mark a series of firsts: the first time a woman, a person of color and a non-American will venture on a Moon mission.

It is also the inaugural crewed flight of NASA’s new lunar rocket, dubbed SLS.

The mammoth orange-and-white rocket is designed to allow the United States to repeatedly return to the Moon in years to come, with the goal of establishing a permanent base that will offer a stepping stone for further exploration.

But getting it off the ground has not been simple. The Artemis 2 mission was originally due to take off as early as February but repeated setbacks stalled that goal and even necessitated rolling the rocket back to its hangar for analysis and repairs.

And then there is the weather: as of Monday, NASA reported that the forecast shows “an 80 percent chance of favorable weather conditions.”

“Cloud coverage and potential for high winds on the ground” were their primary concerns, the agency said.

Teams are also monitoring solar weather.

“I’m just gonna make an appeal to the space gods, okay?” Kshatriya said to laughter on Monday.