The Atlas V Centaur arrives on Launch Complex 41 at Cape Canaveral Air Force Station in Florida.

The Atlas V/Centaur arrives on Launch Complex-41 at Cape Canaveral Air Force Station in Florida. The Atlas was rolled to the launch pad from the Vertical Integration Facility in preparation for the wet dress rehearsal, or countdown test, which means being fully loaded with propellants including liquid hydrogen, liquid oxygen and RP-1 fuel. The launch vehicle will be rolled off the pad and returned to the VIF on May 16. The Atlas V/Centaur is the launch vehicle for NASA's Lunar Reconnaissance Orbiter, or LRO, and NASA's Lunar CRater Observation and Sensing Satellite, known as LCROSS. They will be mated with the Atlas in late May. LCROSS and LRO are the first missions in NASA's plan to return humans to the moon and begin establishing a lunar outpost by 2020. Launch is scheduled for no earlier than June 17. Photo credit: NASA/Kim Shiflett