WASHINGTON — The launch of three U.S. Air Force satellites July 23 was postponed 24 hours because of a ground system problem at the launch pad, according to a United Launch Alliance spokeswoman.

The trio of satellites comprising the Air Force Space Command (AFSC)-4 mission was scheduled to lift off from Cape Canaveral Air Force Station in Florida shortly after 7 p.m. EDT aboard a United Launch Alliance Delta 4 rocket.

But ULA spokeswoman Jessica Rye said in a statement “an issue with the ground support equipment environmental control system that supports the launch vehicle” forced a scrub with less than two hours left before the planned liftoff.

ULA has rescheduled the launch, pending a solution to the environmental control problem, for July 24 at 6:59 p.m., although weather forecasts only show a 30 percent chance of favorable conditions then, she said.

The primary payload onboard the Delta 4 are two satellites that will serve as the first-generation of the Geosynchronous Space Situational Awareness Program, a previously classified space surveillance system first disclosed in February by Gen. William Shelton, commander of Air Force Space Command.

The rocket will also carry the Automated Navigation and Guidance Experiment for Local Space, or ANGELS, satellite. Managed by the Air Force Research Lab at Kirtland Air Force Base in New Mexico, the satellite is intended to test multiple techniques “for providing a clearer picture of the environment around our vital space elements,” according to an Air Force ANGELS fact sheet.

All three satellites onboard the rocket were built by Orbital Sciences Corp. of Dulles, Virginia.

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Mike Gruss is a senior staff writer for SpaceNews. He joined the publication in January 2013 to cover military space. Previously, he worked as a reporter and columnist for The Virginian-Pilot in Norfolk, Va. and The Journal Gazette in Fort Wayne, Ind. He...