Advanced Extremely High Frequency (AEHF) is a constellation of communications satellites operated by the United States Space Force.

They incorporate frequency-hopping radio technology, as well as phased array antennas that can adapt their radiation patterns in order to block out potential sources of jamming.

[5] When complete, the space segment of the AEHF system will consist of six satellites, which provides coverage of the surface of the Earth between latitudes of 65° north and 65° south.

It extends the "cross-links" among AEHF of earlier Milstar satellites, which makes it much less vulnerable to attacks on ground stations.

As a geosynchronous satellite over the equator, it still needs to be supplemented with additional systems optimized for polar coverage in high latitudes.

Phased array antennas provide super high-gain earth coverages, enabling worldwide unscheduled access for all users, including small portable terminals and submarines.

[citation needed] The payload flight software contains approximately 500,000 lines of real-time, distributed, embedded code executing simultaneously on 25 on-board processors.

With Boeing as the prime contractor and L-3 Communications and Rockwell Collins as major subcontractors, the first FAB-T (Increment 1) was delivered, for use on the B-2 Spirit aircraft, in February 2009.

[14] The program was restructured in October 2004, when the National Security Agency (NSA) did not deliver key cryptographic equipment to the payload contractor in time to meet the launch schedule.

[16] The satellite vehicle's liquid apogee engine (LAE) provided by IHI failed to raise the orbit after two attempts.

[18] While this is believed to have been the primary cause of the failure, a U.S. Department of Defense Selected Acquisition Report adds that fuel loading procedures and unmet thermal control requirements could also have contributed.

Completion of checkout of AEHF-2 was announced on 14 November 2012 and control turned over to the 14th Air Force for operations for an expected 14-year service life through 2026.

[27] The sixth AEHF satellite was launched on 26 March 2020 at 20:18 UTC by an Atlas V 551 from Cape Canaveral Space Force Station (CCSFS), SLC-41.