WASHINGTON — The U.S. Air Force is investigating an anomaly with the propulsion system on its first Advanced Extremely High Frequency (AEHF) secure communications satellite and may alter its orbital maneuvering plan, the service announced Aug. 20.

The satellite was launched Aug. 14, and an unspecified problem occurred when operators fired the spacecraft’s thrusters to boost it to its designated testing orbit, Air Force Col. Dave Madden, the service’s military satellite communications program director, said in a press release. The satellite and all its subsystems remain safe and stable, and engineers are considering possible changes the orbital boosting process, it said.

The long-delayed AEHF constellation, built by Lockheed Martin Space Systems of Sunnyvale, Calif., will replace the military’s existing Milstar fleet for handling the most critical U.S. military communications. Lockheed Martin is under contract to deliver four AEHF spacecraft.