The launch of the Delta IV rocket from Cape Canaveral Air Force Station has been scrubbed on Wednesday because of an issue during fueling.
The 206-foot Delta IV, equipped with two strap-on solid rocket motors, is carrying the first of two pairs of Air Force satellites will boost into the vicinity of geosynchronous orbit 22,300 miles over the equator, where satellites appear stationary from the ground.
Flying above and below that belt, the Geosynchronous Space Situational Awareness Program spacecraft will watch out for potential threats to critical military and commercial assets and possibly help diagnose any problems those satellites experience.
The rocket is also carrying a small, experimental Air Force satellite called ANGELS, which will perform maneuvers around the rocket's spent upper stage in a higher orbit, demonstrating technologies that also could be used to inspect satellites.
The launch would be the 27th by a Delta IV rocket, and Colorado-based ULA's 33rd for the U.S. Air Force.
It's not clear when a new launch date will be set.