SpaceX’s Dragon spaceship, carrying more than 4,100 pounds of cargo and research specimens, descended to a predawn splashdown Monday in the Pacific Ocean southwest of Los Angeles, completing the first re-flight of one of SpaceX’s unpiloted supply ships to the International Space Station.

Ground crews transferred an Antares rocket out of an assembly building to a launch pad on Virginia’s Eastern Shore in a major step before liftoff on Orbital Sciences’ third flight to resupply the International Space Station.

Orbital ATK’s Antares rocket will deliver the commercial Cygnus supply ship to an orbit with an altitude between 117 miles (189 kilometers) and 184 miles (296 kilometers) within about nine minutes of liftoff Saturday from Virginia’s Eastern Shore.