Photos: Gantry retracted from Atlas 5

The nation’s existing Atlas and Delta launch sites are vying for a future when United Launch Alliance completes its modernization with a new rocket system and downsizing to one pad on each coast.

United Launch Alliance teams loaded super-cold liquid hydrogen and liquid oxygen into an Atlas 5 rocket Friday at Cape Canaveral during a countdown dress rehearsal for a planned launch next month with the Solar Orbiter mission, a robotic spacecraft to study the origins of the solar wind and image the sun’s poles for the first time.

A space-bound NASA satellite was hauled aboard a military transport aircraft from a Southern California factory to the launch site in Florida on Friday and its United Launch Alliance Atlas 5 rocket booster arrived by sea from the manufacturing plant in Alabama today.