The U.S. Air Force and United Launch Alliance (ULA) have discovered an anomaly in an RS-68 engine, prompting officials to delay for one day plans to launch a military wideband communications satellite.

“A unit recently experienced an anomaly in vibration testing and it was determined that this anomaly was caused by variability in how some wiring is installed within the Engine Control Unit,” says ULA spokeswoman Jessica Rye of Boeing’s fifth Wideband Global Satcom (WGS) spacecraft. ULA builds and operates the Delta IV vehicle family.

Launch aboard a Delta IV was slated for May 22. It has now been rescheduled for a 32-min. window starting at 8:28 EDT May 23, Rye says.

ULA is replacing the engine control unit on the Delta IV slated for the WGS-5 mission with one that has been “inspected and confirmed to not have the suspect condition that caused the recent anomaly in acceptance testing,” Rye says.

WGS-5 is the final satellite required to declare full operational capability for the constellation; this is likely early next year.

Once called the Wideband Gapfiller Satellite program, the project originally was only intended to plug a gap in capability. But the Air Force eventually decided to buy 10 of the spacecraft.

WGS-5 will be placed in geosynchronous orbit over the East Coast; the first four satellites were placed between the Eastern Atlantic Ocean and Western Pacific Ocean to service deployed forces.

Though WGS is replacing the legacy Defense Satellite Communications System constellation, some of those satellites are still operational.

WGS will service U.S. forces in addition to partners that have participated financially in the project. They are Australia, Canada, Denmark, Luxembourg, the Netherlands and New Zealand.