Live coverage: Atlas 5 countdown and launch journal

This video released by United Launch Alliance shows the Delta 4-Heavy rocket’s predawn liftoff Aug. 12 from the perspective of a downward-facing camera, capturing dazzling views of the fiery takeoff and the dramatic separation of the launcher’s two hydrogen-fueled boosters.

Arianespace’s third Ariane 5 launch of the year was set liftoff Friday from Kourou, French Guiana, but an issue with a sensor on the rocket’s first stage liquid hydrogen tank caused officials to scrub the launch attempt. The Ariane 5 is poised to carry three U.S.-built commercial satellites into orbit, while testing a few rocket upgrades, including a modified fairing needed for the launch of the James Webb Space Telescope next year.

United Launch Alliance teams rolled the Mobile Service Tower away from a Delta 4-Heavy rocket at Cape Canaveral’s Complex 37B launch pad Wednesday in preparation for liftoff on a national security mission.