Encyclopedia Astronautica

The Advanced Extremely High Frequency (AEHF) satellite program was the next generation of global, highly secure, survivable communications system for all services of the US Department of Defense, replacing the Milstar series. The first was finally launched three years behind schedule at a cost that had doubled from the original $5 billion estimate.

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 provideed 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 crosslinked 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 permited 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 providd 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).

AKA: Advanced Extremely High Frequency.
Status: Operational.
Gross mass: 6,168 kg (13,598 lb).
First Launch: 2010.08.14.
Last Launch: 2010.08.14.
Number: 1 .

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Associated Countries
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Associated Launch Vehicles
Associated Launch Sites
  • Cape Canaveral America's largest launch center, used for all manned launches. Today only six of the 40 launch complexes built here remain in use. Located at or near Cape Canaveral are the Kennedy Space Center on Merritt Island, used by NASA for Saturn V and Space Shuttle launches; Patrick AFB on Cape Canaveral itself, operated the US Department of Defense and handling most other launches; the commercial Spaceport Florida; the air-launched launch vehicle and missile Drop Zone off Mayport, Florida, located at 29.00 N 79.00 W, and an offshore submarine-launched ballistic missile launch area. All of these take advantage of the extensive down-range tracking facilities that once extended from the Cape, through the Caribbean, South Atlantic, and to South Africa and the Indian Ocean. More...

AEHF Chronology

2010 August 14 - . 11:07 GMT - . Launch Site: Cape Canaveral. Launch Complex: Cape Canaveral LC41. Launch Pad: SLC41. LV Family: Atlas V. Launch Vehicle: Atlas V 531.
  • USA 214 - . Payload: AEHF SV-1. Nation: USA. Agency: Martin. Class: Communications. Type: Military communications satellite. Spacecraft: AEHF. USAF Sat Cat: 36868 . COSPAR: 2010-039A. Apogee: 51,018 km (31,701 mi). Perigee: 12,053 km (7,489 mi). Inclination: 9.9000 deg. Period: 1,224.50 min. First USAF Advanced EHF communications satellite. Placed in an initial 221 x 50179 km x 22.2 deg geosynchronous transfer orbit by the Atlas Centaur upper stage. However the satellite's main BT-4 engine failed, meaning the secondary hydrazine thrusters were used to much more satellite raise the spacecraft to geosynchronous orbit.

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