Advanced Extremely High Frequency (AEHF) is a series of communications satellites operated by the United States Air Force Air Force Space Command. The spacecraft will be used to relay secure communications for the Armed Forces of the United States, the British Armed Forces, the Canadian Forces and the military of the Netherlands. The system will consist of six spacecraft in geostationary orbits, of which two have been launched. AEHF will replace the older Milstar system and will operate at 44 GHz Uplink (EHF band) and 20 GHz Downlink (SHF band).
AEHF spacecraft use a large number of narrow spot beams directed towards the Earth to relay communications to and from users. Crosslinks between the satellites will allow them to relay communications directly without the need to relay them to a ground station first. The satellites are designed to provide jam-resistant communications with a low probability of interception, and incorporate frequency-hopping. The spacecraft are equipped with adaptive antennas which can be used to cast antenna nulls towards sources of jamming.
AEHF incorporates the existing Milstar low data-rate and medium data-rate signals, providing 75–2400 bit/s and 4.8 kbit/sec–1.544 Mbit/s respectively. It also incorporates a new signal, allowing data rates of up to 8.192 Mbit/s. When complete, the space segment of the AEHF system will consist of six satellites. which will provide coverage of the surface of the Earth between latitudes of 65 degrees north and 65 degrees south.
The initial contract for the design and development of the AEHF satellites was awarded to Lockheed Martin Space Systems and Northrop Grumman Space Technology in November 2001, and covered the System Development and Demonstration phase of the program. The contract covered the construction and launch of three satellites, and the construction of a mission control segment. The contract was managed by the MILSATCOM Program Office of the United States Air Force Space and Missile Systems Center. Like the Milstar system, AEHF will be operated by the 4th Space Operations Squadron, located at Schriever Air Force Base.
Read more about Advanced Extremely High Frequency: First AEHF Satellite (USA-214), Second AEHF Satellite (USA-235)
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