Advanced Extremely High Frequency
Encyclopedia
Advanced Extremely High Frequency (AEHF) is a series of communications satellite
s 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 four spacecraft in geostationary orbit
s, of which one has 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 antenna
s 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 four satellites. which will provide coverage of the surface of the Earth between latitude
s 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
.
The first satellite, USA-214
, was successfully launched by an Atlas V
531 rocket on 14 August 2010, from Space Launch Complex 41 at the Cape Canaveral Air Force Station
. This occurred four years behind scheduled; when the contract was awarded in 2000 the first launch was expected to occur in 2006. The National Security Agency
has supposedly been blamed for being insufficiently responsive in providing cryptographic unit
s..
Although the launch was successful, the satellite vehicle's Liquid Apogee Engine has failed to accelerate the vehicle after 2 attempted burns. The Liquid Apogee Engine was meant to raise the satellite vehicle into the correct orbit. The satellite is now being raised to the correct orbit with smaller electric Hall current thrusters, but it will take longer than it would with the LAE. This has caused delays, as the second and third satellite vehicle LAEs had to be analyzed. The investigation into the propulsion anomaly has been completed (but not yet publicly released) and the remaining launch vehicles have been declared flight ready.
A Government Accounting Office report released in July 2011 stated that the blocked fuel line in the Liquid Apogee Engine was most likely caused by a piece of cloth inadvertently left in the line during the manufacturing process.
Additionally, satellite access will also be delayed to no earlier than October of 2011, which will push system testing to a later date.
Communications satellite
A communications satellite is an artificial satellite stationed in space for the purpose of telecommunications...
s operated by the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
Air Force
United States Air Force
The United States Air Force is the aerial warfare service branch of the United States Armed Forces and one of the American uniformed services. Initially part of the United States Army, the USAF was formed as a separate branch of the military on September 18, 1947 under the National Security Act of...
Air Force Space Command
Air Force Space Command
Air Force Space Command is a major command of the United States Department of the Air Force, with its headquarters at Peterson Air Force Base, Colorado. AFSPC supports U.S. military operations worldwide through the use of many different types of satellite, launch and cyber operations....
. The spacecraft will be used to relay secure communications for the Armed Forces of the United States, the British Armed Forces
British Armed Forces
The British Armed Forces are the armed forces of the United Kingdom of Great Britain and Northern Ireland.Also known as Her Majesty's Armed Forces and sometimes legally the Armed Forces of the Crown, the British Armed Forces encompasses three professional uniformed services, the Royal Navy, the...
, the Canadian Forces
Canadian Forces
The Canadian Forces , officially the Canadian Armed Forces , are the unified armed forces of Canada, as constituted by the National Defence Act, which states: "The Canadian Forces are the armed forces of Her Majesty raised by Canada and consist of one Service called the Canadian Armed Forces."...
and the military of the Netherlands
Military of the Netherlands
The Armed forces of the Netherlands consist of the Army, Navy, and Air Force.The service branches consist of:* Koninklijke Landmacht , Royal Netherlands Army....
. The system will consist of four spacecraft in geostationary orbit
Geostationary orbit
A geostationary orbit is a geosynchronous orbit directly above the Earth's equator , with a period equal to the Earth's rotational period and an orbital eccentricity of approximately zero. An object in a geostationary orbit appears motionless, at a fixed position in the sky, to ground observers...
s, of which one has been launched. AEHF will replace the older Milstar system and will operate at 44 GHz Uplink (EHF
EHF
EHF may stand for:* EHF – therapy * Extremely High Frequency, a radio frequency band* Ebola hemorrhagic fever, an illness* European Handball Federation, the European governing body for handball...
band) and 20 GHz Downlink (SHF
Super high frequency
Super high frequency refers to radio frequencies in the range of 3 GHz and 30 GHz. This band of frequencies is also known as the centimetre band or centimetre wave as the wavelengths range from ten to one centimetres....
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 antenna
Antenna (radio)
An antenna is an electrical device which converts electric currents into radio waves, and vice versa. It is usually used with a radio transmitter or radio receiver...
s 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 four satellites. which will provide coverage of the surface of the Earth between latitude
Latitude
In geography, the latitude of a location on the Earth is the angular distance of that location south or north of the Equator. The latitude is an angle, and is usually measured in degrees . The equator has a latitude of 0°, the North pole has a latitude of 90° north , and the South pole has a...
s 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
Lockheed Martin
Lockheed Martin is an American global aerospace, defense, security, and advanced technology company with worldwide interests. It was formed by the merger of Lockheed Corporation with Martin Marietta in March 1995. It is headquartered in Bethesda, Maryland, in the Washington Metropolitan Area....
and Northrop Grumman Space Technology
Northrop Grumman
Northrop Grumman Corporation is an American global aerospace and defense technology company formed by the 1994 purchase of Grumman by Northrop. The company was the fourth-largest defense contractor in the world as of 2010, and the largest builder of naval vessels. Northrop Grumman employs over...
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
Space and Missile Systems Center
The Space and Missile Systems Center is a part of Air Force Space Command of the United States Air Force. SMC is the Air Force’s product center for the development and acquisition of space and missile systems...
. Like the Milstar system, AEHF will be operated by the 4th Space Operations Squadron
4th Space Operations Squadron
The United States Air Force's 4th Space Operations Squadron is a satellite operations unit located at Schriever AFB, Colorado...
, located at Schriever Air Force Base
Schriever Air Force Base
Schriever Air Force Base is a base of the United States Air Force located approximately 10 miles east of Peterson AFB near Colorado Springs in El Paso County, Colorado, United States.-Overview:...
.
The first satellite, USA-214
USA-214
USA-214, known before launch as Advanced Extremely High Frequency 1 or AEHF SV-1, is a military communications satellite operated by the United States Air Force...
, was successfully launched by an Atlas V
Atlas V
Atlas V is an active expendable launch system in the Atlas rocket family. Atlas V was formerly operated by Lockheed Martin, and is now operated by the Lockheed Martin-Boeing joint venture United Launch Alliance...
531 rocket on 14 August 2010, from Space Launch Complex 41 at the Cape Canaveral Air Force Station
Cape Canaveral Air Force Station
Cape Canaveral Air Force Station is an installation of the United States Air Force Space Command's 45th Space Wing, headquartered at nearby Patrick Air Force Base. Located on Cape Canaveral in the state of Florida, CCAFS is the primary launch head of America's Eastern Range with four launch pads...
. This occurred four years behind scheduled; when the contract was awarded in 2000 the first launch was expected to occur in 2006. The National Security Agency
National Security Agency
The National Security Agency/Central Security Service is a cryptologic intelligence agency of the United States Department of Defense responsible for the collection and analysis of foreign communications and foreign signals intelligence, as well as protecting U.S...
has supposedly been blamed for being insufficiently responsive in providing cryptographic unit
Encryption
In cryptography, encryption is the process of transforming information using an algorithm to make it unreadable to anyone except those possessing special knowledge, usually referred to as a key. The result of the process is encrypted information...
s..
Although the launch was successful, the satellite vehicle's Liquid Apogee Engine has failed to accelerate the vehicle after 2 attempted burns. The Liquid Apogee Engine was meant to raise the satellite vehicle into the correct orbit. The satellite is now being raised to the correct orbit with smaller electric Hall current thrusters, but it will take longer than it would with the LAE. This has caused delays, as the second and third satellite vehicle LAEs had to be analyzed. The investigation into the propulsion anomaly has been completed (but not yet publicly released) and the remaining launch vehicles have been declared flight ready.
A Government Accounting Office report released in July 2011 stated that the blocked fuel line in the Liquid Apogee Engine was most likely caused by a piece of cloth inadvertently left in the line during the manufacturing process.
Additionally, satellite access will also be delayed to no earlier than October of 2011, which will push system testing to a later date.