Watch a live view of the Atlas 5 launch pad with countdown audio (members only)

Launch of an Atlas 5 rocket from Cape Canaveral with a U.S. Air Force infrared surveillance satellite was scrubbed Thursday evening after engineers encountered a balky valve associated with the first stage’s liquid oxygen system.

A United Launch Alliance Atlas 5 rocket with a new type of solid rocket booster emerged from its hangar Tuesday evening for the 1,800-foot rollout to pad 41 at Cape Canaveral, moving into position for liftoff Wednesday with a classified National Reconnaissance Office payload.

A United Launch Alliance Atlas 5 rocket blasted off from Cape Canaveral at 6:28 a.m. EDT (1028 GMT) today to deploy the Mexican Morelos 3 mobile communications satellite.