The Space Launch System (SLS) rocket and the Orion spacecraft are seen at the Kennedy Space Center in Cape Canaveral, Fla., on Sunday. Miguel J. Rodriguez Carrillo/AFP via Getty Images hide caption toggle caption Miguel J. Rodriguez Carrillo/AFP via Getty Images Preparations are underway to begin critical testing of NASA spacecraft for the Artemis II mission that will send four astronauts around the moon. Fuel testing is set to begin Monday, NASA says. The fueling phase of prelaunch testing known as a “wet dress rehearsal” was delayed because of freezing temperatures at the launch pad located at NASA’s Kennedy Space Center in Florida. Here is what to know about preparations and the mission. What exactly is a wet dress rehearsal? A wet dress rehearsal is a designated time before launch when engineers and crew conduct testing of the spacecraft. During this final test, the Orion spacecraft that will house the astronauts and the Space Launch System (SLS) rocket will be checked over the course of a detailed countdown schedule. A countdown clock began at 8:13 …