The satellite, built by Lockheed Martin, will join other SBIRS satellites to detect and track missile launches around the world.
About 42 minutes later, the rocket deployed a 10,000-pound addition to an Air Force constellation that serves as a "bell-ringer" warning of ballistic missile launches around the globe, potentially including nuclear threats. But forecasters said the weather is 90 percent favorable for a launch.
The planned flight of a United Launch Alliance Atlas V 411 rocket has been scrubbed by at least 24 hours due to unspecified reasons.
A ULA statement said: "SBIRS, considered one of the nation's highest priority space programs, is created to provide global, persistent, infrared surveillance capabilities to meet 21st century demands in four national security mission areas: missile warning, missile defence, technical intelligence and battle-space awareness". The satellite is set to launch January 18 from Cape Canaveral Air Force Station, FL, at 7:52 p.m. and will fly on a United Launch Alliance Atlas V rocket.
The Atlas V, made and operated by United Launch Alliance, launched the three previous SBIRS satellites that all went to the same orbit.
The ULA has already confirmed that the countdown to launch is underway, adding that this is one of the USA's "highest priority" missions.
The Air Force's SBIRS includes a combination of satellites in GEO orbit and hosted payloads in Highly Elliptical Orbit (HEO).