Photos: Predawn launch of Atlas 5

On its third flight Monday night, SpaceX’s Falcon Heavy rocket will fly to three different orbits with two dozen spacecraft on a mission set to last more than six hours, prompting SpaceX founder Elon Musk to declare it the company’s “most difficult launch ever.”

Following delivery to the launch pad, the United Launch Alliance Atlas 5 rocket stands poised for the NROL-61 mission for the National Reconnaissance Office from Cape Canaveral on Thursday morning.

China launched a Beidou navigation satellite Friday using a Long March 3C rocket, adding another node to a growing space-based network that Chinese officials say will broadcast positioning and timing signals around the world next year.