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USS Lake Champlain, a Ticonderoga-class Aegis guided missile cruiser, launched in 1987. This version is equipped with the MK 41 VLS system, whereas earlier versions were equipped with the Mark-26 twin-arm missile launcher system.

The Aegis Combat System is an integrated naval weapons system developed by the Missile and Surface Radar Division of RCA, and now produced by Lockheed Martin. It uses powerful computers and radars to track and guide weapons to destroy enemy targets.

Initially used by the United States Navy, Aegis is now used also by the Japan Maritime Self-Defense Force, Spanish Navy, Royal Norwegian Navy, and Republic of Korea Navy. Over 100 Aegis-equipped ships have been deployed in five navies worldwide. The Royal Australian Navy has selected the Aegis system for placement on its new Air Warfare Destroyers.

The word "Aegis" is a reference that dates back to Greek mythology, with connotations of a protective shield.



Combat Information Center (CIC) consoles aboard USS Normandy, 1997.

The Aegis Combat System (ACS) is an advanced command and control (Command and Decision, or C&D, in Aegis parlance), and Weapon Control System (WCS) that uses powerful computers and radars to track and guide weapons to destroy enemy targets.

The ACS is composed of the Aegis Weapon System (AWS), the fast-reaction component of the Aegis Anti-Aircraft Warfare (AAW) capability, along with the Phalanx Close In Weapon System (CIWS), the MK 41 VLS[1], Anti-Submarine Warfare (ASW) systems, and Tomahawk Land Attack Cruise Missiles (TLAM). Shipboard torpedo and naval gunnery systems are also integrated.

AWS, the heart of Aegis, comprises the AN/SPY-1 Radar, MK 99 Fire Control System, WCS, the Command and Decision Suite, and SM-2 Standard Missile systems. The Aegis Combat System is controlled by an advanced, automatic detect-and-track, multi-function three-dimensional passive electronically scanned array radar, the AN/SPY-1. Known as "the Shield of the Fleet", the SPY high-powered (six megawatt) radar is able to perform search, tracking, and missile guidance functions simultaneously with a track capacity of well over 100 targets at more than 100 nautical miles (190 km).[2]

The Aegis system communicates with the Standard missiles through a radio frequency (RF) uplink using the AN/SPY-1 radar for midcourse guidance of the missile during engagements, but still requires the AN/SPG-62 radar for terminal guidance. This means that with proper scheduling of intercepts, a large number of targets can be engaged simultaneously.

The computer-based command-and-decision element is the core of the Aegis Combat System. This interface makes the ACS capable of simultaneous operation against almost all kinds of threats. The Aegis Ballistic Missile Defense System program is intended to enable the Aegis system to act in a Sea-based Ballistic Missile Defense function, to counter short- and medium-range ballistic missiles of the variety typically employed by a number of potential opponent states.


Aegis was initially developed by the Missile and Surface Radar Division of RCA, which was then acquired by General Electric. The division responsible for the Aegis systems became Government Electronic Systems. This, and other GE Aerospace businesses, were sold to Martin Marietta in 1992.[3] This became part of Lockheed Martin during 1995.

Large screen displays on USS Vincennes, typical of early Aegis platforms

By the late 1950s, the US Navy replaced guns with guided missiles on its ships. These were sufficient weapons but by the late 1960s, the U.S. Navy recognized that reaction time, firepower, and operational availability in all environments did not match the anti-ship missile threat.[citation needed]

As a result, the US Navy decided to develop a program to defend ships from anti-ship missile threats. An Advanced Surface Missile System (ASMS) was promulgated and an engineering development program was initiated to meet the requirements. ASMS was re-named "Aegis" in December 1969 after the aegis, the shield of the Greek god Zeus. The name was invented at the suggestion of Captain L. J. Stecher, a former Tartar Weapon System manager, after an internal U.S. Navy contest to name the ASMS program was initiated. Captain Stecher also submitted a possible acronym of Advanced Electronic Guided Interceptor System although this definition was never used.[4] While many other meanings have been attributed to the name Aegis, the name is not an acronym: it is named for a mythological shield possessed by the Greek god Zeus. The main manufacturer of the Aegis combat system, Lockheed Martin, makes no mention of it being an acronym, nor does the U.S. Navy.

Because the Aegis combat system is the key component of several cruiser and destroyer class vessels, the ships are often incorrectly referred to as "Aegis class cruisers" or "Aegis class destroyers". In reality, the radar system and the class of ship it is installed on are unrelated to each other.

Large screen displays on USS John S. McCain, circa 1997. Destroyers have two displays while cruisers have four.

The first Engineering Development Model (EDM-1) was installed in a test ship, the USS Norton Sound, in 1973. During this time frame, the Navy envisioned installing the Aegis combat system on both a nuclear powered "Strike Cruiser" (or CSGN) and a conventionally powered destroyer (originally designated DDG 47). The CSGN was to be a new, 17,200 ton cruiser design based on the earlier California- and Virginia-class cruisers. The Aegis destroyer design would be based on the gas turbine powered Spruance class. When the CSGN was cancelled, the Navy proposed a modified Virginia class design (CGN 42) with a new superstructure designed for the Aegis combat system and with a displacement of 12,100 tons. As compared to the CSGN, this design was not as survivable and had reduced command and control facilities for an embarked flag officer. Ultimately this design was also cancelled during the Carter Administration due to its increased cost compared to the non-nuclear DDG 47. With the cancellation of the CGN 42, the DDG 47 Aegis destroyer was redesignated as CG 47, a guided missile cruiser.

The first cruiser of this class was the Ticonderoga, which uses two twin-armed Mark-26 missile launchers, fore and aft. The commissioning of the sixth ship of the class, the Bunker Hill opened a new era in surface warfare as the first Aegis ship outfitted with the Martin Marietta Mark-41 Vertical Launching System (VLS), allowing a wider missile selection, more firepower, and survivability. The improved AN/SPY-1B radar went to sea in the Princeton, ushering in another advance in Aegis capabilities. The Chosin introduced the AN/UYK-43/44 computers, which provide increased processing capabilities.

During 1980, a destroyer was designed using an improved sea-keeping hull form, reduced infrared, and radar cross-section and upgrades to the Aegis Combat System. The first ship of the Arleigh Burke class, the USS Arleigh Burke, was commissioned during 1991.

Flight II of the Arleigh Burke class, introduced in 1992, incorporated improvements to the SPY radar, and to the Standard missile, active electronic countermeasures, and communications. Flight IIA, introduced in 2000, added a helicopter hangar with one anti-submarine helicopter and one armed attack helicopter. The Aegis program has also projected reducing the cost of each Flight IIA ship by at least $30 million.

Iran Air Flight 655

Layout of the Combat Information Center of early Aegis Cruisers.

The Aegis system was involved in a disaster in which USS Vincennes shot down Iran Air Flight 655 during 1988 resulting in 290 civilian deaths. The system has never defended a ship from a real threat.

It was determined by a formal military investigation[5] that the Aegis system was completely operational and did not have any maintenance problems. The investigation ruled that had the Commanding officer relied on the complete tactical data displayed by the Aegis system the engagement might never have occurred. Additionally, psychological effects of the crew subconsciously manipulating the data to accord with a predefined scenario greatly contributed to the false identification. The investigation found that the Aegis Combat System did not contribute to the incident, but did aid in the investigation by means of recorded target data. The discrepancies are as follows:

Aegis Data Report Personnel Report To CO
Iran Air Flight 655 continuously ascended in duration of flight Iran Air Flight 655, after attaining 9000 to 12,000 ft (3,700 m)., reportedly descended on an attack vector on USS Vincennes
Iran Air Flight 655 continuously squawked Mode III (Civilian Airliner) identification, friend or foe (IFF) in duration of flight Iran Air Flight 655 reportedly squawked Mode II (Iranian F-14 Tomcat) IFF for a moment; personnel proceeded to re-label the target from "Unknown Assumed Enemy" to "F-14"
Iran Air Flight 655 held consistent climb speed in duration of flight Iran Air Flight 655 was reported to increase in speed to an attack vector similar to an F-14 Tomcat

Aegis in other navies

Ship Class Operator Total Ships
Atago  JMSDF 2
Kongō  JMSDF 4
King Sejong the Great Naval Jack of South Korea.svg ROKN 2
Álvaro de Bazán  AE 6
Fridtjof Nansen  RNoN 5
Arleigh Burke  USN 57 (70)
Ticonderoga  USN 22
Total 98
  • The Australian government, by its Sea 4000 project to acquire three air warfare destroyers, decided during August 2004 that Aegis would be the core of the combat system for the Royal Australian Navy ships.

On 20 June 2007, the Spanish government announced it had selected the Navantia F-100 Álvaro de Bazán class design over a variant of the Arleigh Burke design. The Australian variant will be known as the Hobart class.

  • The Japanese government operates four Kongō-class destroyers of a modified Arleigh Burke design from 1993. Two improved units known as the Atago class were purchased in 2000 and the first ship of this class, DDG 177 Atago, was commissioned March 15, 2007.
  • The government of Norway is procuring five ships of Spanish manufacture which include a U.S. sourced Aegis system integrated onto the ships, as the Fridtjof Nansen class. The first unit of this type, Fridtjof Nansen, was launched on June 3, 2004. The second of five Norwegian Nansen class frigates, the Roald Amundsen, completed its sea trials and entered service in June 2007. The 5,200 ton Nansen class ships are being built in Spain and cost $600 million each.
  • Republic of Korea is building Aegis variants of its KDX destroyers, called KDX-III. The first ship of the class, King Sejong the Great, was launched on May 25, 2007. The second Aegis destroyer was launched in November 2008 and was given the name Yulgok Yi I. South Korea commissioned a third KDX-III in September of 2008 which is scheduled to be completed in 2012.
  • The government of Spain is currently operating four Álvaro de Bazán class Aegis frigates, with a fifth ship under construction.

See also


  1. ^ Originally, the first five ships of the United States' Aegis equipped Ticonderoga class cruisers were outfitted with Mark-26 twin-arm missile launchers; however, the ships with this system have been decommissioned and are no longer in service.
  2. ^ "Aegis Combat System". The Warfighter Encyclopedia. Warfighter Response Center. 2003-10-08. Retrieved 2006-08-10. .
  3. ^ Lenorovitz, Jeffrey. "GE Aerospace to merge into Martin Marietta" Aviation Week & Space Technology. 1992-11-30. Accessed on 2007-07-19
  4. ^ Lockheed Martin. "Aegis Heritage". Presentation. November 20, 2002.
  5. ^ Fogarty, William M. (July 28, 1988), Formal Investigation into the Circumstances Surrounding the Downing of Iran Air Flight 655 on 3 July 1988, 93-FOI-0184,, retrieved 2006-03-31 

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