Photos: Atlas 5 rocket soars from West Coast

Poised for its one and only satellite launch of the year, the National Reconnaissance Office will conduct a hush-hush flight Thursday using a United Launch Alliance Atlas 5 rocket from California.

SpaceX’s Falcon 9 rocket ignited its main engines at Cape Canaveral’s Complex 40 launch pad Thursday night, clearing a major hurdle before liftoff May 31 with the SES 12 communications satellite.

A team of United Launch Alliance and NASA engineers worked through Delta 2 launch day fueling procedures during a simulated countdown Wednesday for what should be the second-to-last time before the venerable rocket’s final liftoff next month from California’s Central Coast.