CAPE CANAVERAL, Fla. — NASA began a two-day practice countdown Saturday leading up to the fueling of its new moon rocket, a crucial test that will determine when four astronauts blast off on a lunar flyby.

Currently in quarantine to avoid germs, Commander Reid Wiseman and his crew will be the first individuals to launch to the moon since 1972. They will monitor the dress rehearsal from their Houston base before flying to Kennedy Space Center once the rocket is cleared for flight.

The 322-foot Space Launch System rocket has been positioned on the launch pad for two weeks. If Monday’s fueling test proves successful, NASA could attempt a launch within the next week. This milestone will mark the filling of the rocket’s tank with over 700,000 gallons of super-cold fuel, stopping just half a minute short of when the engines would ignite.

Weather issues, particularly a bitter cold spell, delayed the fueling demo and launch by two days, now setting February 8 as the earliest possible launch date.

On board the Orion capsule atop the rocket, U.S. and Canadian astronauts will make a swift trip around the moon, returning directly back without any planned stops until splashdown in the Pacific, with the entire mission expected to last nearly 10 days.