CAPE CANAVERAL, Fla. (AP) — NASA commenced a two-day practice countdown on Saturday in preparation for the fueling of its new moon rocket, a critical test that will dictate when four astronauts will embark on a lunar flyby.

Commander Reid Wiseman and his crew are already quarantined to prevent exposure to germs and will be the first humans to fly to the moon since the Apollo program in 1972. They will monitor the dress rehearsal from their base in Houston before heading to Kennedy Space Center once the rocket receives the green light for flight.

The towering 322-foot (98-meter) Space Launch System rocket, which was moved to the launch pad two weeks ago, is set to be fueled with over 700,000 gallons of super-cold propellant. The countdown will culminate just short of a fully ignited launch, with Monday's fueling test being a significant factor in determining the timing of the launch, potentially as early as a week from now.

A cold snap previously postponed the fueling demonstration, also affecting the planned launch timeline. The earliest opportunity for liftoff is now pegged for February 8.

Onboard the Orion capsule situated atop the rocket, the American and Canadian astronauts will circle around the moon and return directly back to Earth without any stops, in a mission that is expected to last approximately 10 days.

Since the conclusion of the Apollo program, which sent 24 astronauts to the moon, of whom 12 walked on its surface, the Artemis II mission signifies a new chapter in lunar exploration for NASA.