Live coverage: Atlas 5 countdown and launch journal

Towering more than 30 stories tall, the mobile gantry structure at the Delta 4-Heavy rocket’s launch pad at Cape Canaveral was wheeled into position for liftoff of the triple-core launcher Thursday with a classified payload for the National Reconnaissance Office.

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.

The full broadcast of the Atlas 5 NROL-55 / Cubsat launch. (Membership required)