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AEHF

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AKA: Advanced Extremely High Frequency. First Launch: 2010-08-14. Last Launch: 2013-09-18. Number: 3 . Gross mass: 6,168 kg (13,598 lb).

In Nov. 2001, the U.S. Air Force awarded Lockheed Martin Space Systems and Northrop Grumman Space Technology (Formerly TRW Space & Electronics) a $2.698 billion contract to begin the System Development and Demonstration (SDD) phase of the Advanced Extremely High Frequency (Advanced EHF) Program.

The SDD phase was to have deployed two Advance EHF satellites and the Advance EHF mission control segment. The new mission control segment supported both Milstar and AEHF. Lockheed Martin was the developer of the ground segment, satellite bus provider, space vehicle integrator and overall systems integrator and prime contractor. Northrop Grumman provided the payload and associated components (digital processor and RF equipment).

The Advanced EHF Program was the follow-on to the DoD's Milstar highly secure communication satellite program, which had a four-satellite operational constellation. The last Milstar satellite was successfully launched in April 2003.

The fully operational Advanced EHF constellation was to consist of four cross-linked satellites providing coverage of the Earth from 65 degrees north latitude to 65 degrees south. A fifth satellite was to be built as a spare or launched to provide additional capability to the envisioned constellation. This original constellation and ground segment were to cost $5 billion. This was cut back to three satellites in-orbit and no spare in 2002 when AEHF was expected to be replaced by the TSAT (Transformational Satellite communications system). After expenditure of $2.5 billion, TSAT was cancelled in 2005 and AEHF was increased to three on-orbit satellites and one spare. However cost ballooned to over $10 billion and date of the first satellite launch slipped from 2007 to late 2010.

Advanced EHF satellites provided 10 times greater total capacity and offered channel data rates six times higher than that of Milstar II communications satellites. The higher data rates permitted transmission of tactical military communications such as real-time video, battlefield maps and targeting data.

Advanced EHF added new higher data rate modes to the low data rate and medium data rate modes of Milstar II satellites. The higher data rate modes provided data rates up to 8.2 million bits of data per second (Mbps) to Advanced EHF Army terminals. Each Advanced EHF satellite employed more than 50 communications channels via multiple, simultaneous downlinks. For global communications, the Advanced EHF system used inter-satellite crosslinks, eliminating the need to route messages via terrestrial systems.

The three AEHF communication services were: the new high data rate (HDR) at up to 8.192 Mbps per user; and the previous Milstar Low Data Rate (LDR) services (75 – 2400 bits per second) and Milstar Medium Data Rate (MDR) services (4.8 kbit/s – 1.544 Mbit/s).