Patriot Credit - via Andreas Parsch

Surface-to-air missile. IOC: 1982. Country: USA. Status: Active. Department of Defence Designation: MIM-104. Popular Name: Patriot.

Standard Army surface-to-air missile. Later versions had anti-tactical missile capability.

Historical Essay © Andreas Parsch

Raytheon MIM-104 Patriot

The MIM-104 Patriot is the most advanced medium/long-range surface-to-air missile in current operational U.S. Army inventory, and is the only SAM to have intercepted ballistic missiles in combat. The Patriot system, complemented by the new PAC-3 missile, will remain the Army's main tactical air-defense system for some time in the future.

Studies for an advanced surface-to-air missile to supplement and eventually replace the MIM-23 Hawk already began in 1961 under the FABMDS (Field Army Ballistic Missile Defense System) program. The name was later changed to AADS-70 (Army Air-Defense System - 1970), and finally in 1964 to SAM-D (Surface-to-Air Missile - Development). Specifications were vague and changed frequently, but always included not only the ability to counter aircraft threats of all types, but also an anti-TBM (Theater Ballistic Missiles, a.k.a. short-range ballistic missiles) capability. In May 1967, Raytheon was selected as prime contractor for SAM-D development, and firing trials of SAM-D test missiles began in November 1969. The engineering development phase began in 1973, but in January 1974, a major change in the requirements occurred. It was directed that SAM-D should use Track-Via-Missile (TVM) guidance, i.e. target tracking information is not received by the ground radar directly, but by the missile which transmits it to the ground control station. Because the missile is always nearer to the target than the ground radar, this method significantly enhances accuracy and the ability to discriminate decoys from the real threat. This new requirement of course significantly delayed the development, and full-scale development didn't start until January 1976, after TVM had been demonstrated in tests in 1975. Around that time, the official designation XMIM-104A was assigned, and in May 1976, SAM-D was named Patriot. Testing of the missile and the Patriot ground equipment continued through the late 1970s, and in October 1980, the first production contract for the MIM-104A Patriot missile was issued. In 1984, the Patriot finally reached Initial Operation Capability with its first U.S. Army units.

The MIM-104A missile is powered by a single Thiokol TX-486-1 solid-fueled rocket motor, and armed with a high-explosive blast-fragmentation warhead. The missile is launched from canisters, four of which make up the M901 launching station transported on an M860 semi-trailer. In mid-course, the Patriot is inertially guided with command updates, and for the terminal phase a semi-active radar homing guidance with TVM is employed. The main item of the ground equipment is the AN/MPQ-53 G-band pulse-doppler phased-array multipurpose radar, which is controlled by the AN/MSQ-104 ECS (Engagement Control Station). The ECS is the central control agency for all missiles of a Patriot unit, and automatically coordinates the assignment of missiles to identified targets, and the launches of the individual missiles. The AN/MPQ-53 is used for tracking, IFF, and target-illumination purposes, and also includes the command uplink and TVM downlink channels. The TVM guidance method is particularly efficient in long-range and/or low-altitude engagements, when the ground radar can "see" much less of the energy reflected from the target than the MIM-104's monopulse seeker. Then the "radar image" in the missile's seeker can be used, together with the high computing power of the ECS, to discriminate decoys and calculate the interception path. At the interception point, the missile's warhead is detonated by a radar-proximity fuze.

The MIM-104B, fielded in the late 1980s, is also known as the SOJC (Standoff Jammer Countermeasures) missile and uses a modified guidance and navigation hardware. The MIM-104B adds a surface-to-surface capability against ground-based radar jamming sources to the Patriot system. The missile can fly an optimized (lofted) trajectory towards the jammer, and use its seeker to select the strongest emitter for terminal homing. The anti-aircraft/anti-missile capability is the same as for the MIM-104A.

The most important changes to the Patriot system were made by the PAC (Patriot Advanced Capability, originally Patriot Anti-TBM Capability) program. The interim PAC-1 modification, first flight tested against an MGM-52 Lance target missile in September 1986, incorporated only software changes to the search and track algorithms and the phased-array radar (the maximum elevation angle of the latter was increased from 45° to almost 90°). Because the Patriot missile itself was unchanged, no new MIM-104 designation was allocated. The first PAC-1 systems were fielded in July 1988.

The PAC-2 upgrade includes further software changes, and an improved MIM-104C missile. The MIM-104C has a blast-fragmentation warhead with larger fragments (45 g compared to 2 g for the MIM-104A/B warhead) to increase lethality against ballistic missile warheads. It also has a new pulse-doppler proximity fuze with two beams, a narrow one for missiles, and a broader one for slower aircraft targets. The first test firing of an MIM-104C (against another Patriot missile!) occurred in November 1987, and the first PAC-2 systems were delivered to the field in late 1990. During Operation Desert Storm (ODS) in 1991, PAC-1 and PAC-2 systems were used against Iraqi "Al-Hussein" (modified SS-1 Scud) SRBMs. In most of the ODS engagements, two missiles were automatically fired at an incoming target. The success rate was not bad, but not as overwhelmingly good as the first reports suggested. Furthermore, the "Al-Hussein" was far from the state-of-the-art in missile and countermeasures technology.

The MIM-104D, also known as PAC-2/GEM (Guidance Enhanced Missile), is a further improved MIM-104C. It has a seeker with better performance against low-RCS targets, and an improved fuze against high-speed ballistic missiles. The MIM-104D entered production in 1994.

The designation MIM-104E has been allocated to a variant with further improved detection capability and lethality. I have no details about the upgrades, and don't know whether the MIM-104Es are new-built missiles or conversions of older rounds.

The PAC-3 system incorporates many changes to the ground equipoment and the missile, and is fielded in incremental steps, called Configuration 1, 2, and 3. PAC-3/Conf.1 was first fielded in 1995, and incorporates changes to the ECS, a new pulse-doppler radar processor, and the MIM-104D missile. PAC-3/Conf.2, introduced in 1996, includes Link 16 JTIDS (Joint Tactical Information Distribution System) compatibility and further radar improvements against low-RCS targets and anti-radiation missiles.

The ultimate PAC-3/Conf.3 includes radar upgrades to increase detection in high-clutter environments, an to improve discrimination of closely spaced objects (better decoy recognition). The most important feature of this new Patriot system, however, will be a completely new missile, a variant of the Lockheed-Martin ERINT (Extended Range Interceptor) commonly called PAC-3 (which is a bit confusing because the interim PAC-3 systems don't use this missile). The PAC-3 missile is highly optimized for the anti-missile role (employing a hit-to-kill capability enhanced by a fragmentation warhead), so that operational PAC-3 Patriot units will probably be equipped eventually with both MIM-104D and ERINT/PAC-3 missiles. The latter is significantly smaller than an MIM-104, so that 16 missiles instead of four can be carried in a single launch station. ERINT was first flight-tested in 1992, and selected as the ultimate PAC-3 missile in 1994. The PAC-3/ERINT integration tests took place from 1995 to 1997, and the missile is currently in LRIP (Low Rate Initial Production) status. The operational testing phase began in late 2001, and Initial Operational Capability is currently planned for 2003 (four years after the originally planned date). However, the operational tests in the first half of 2002 were only partially successful, and the decision for full-rate production, initially expected for mid-2002, may be postponed. The PAC-3/ERINT was also selected as the missile component of the joint US/European MEADS (Medium Extended Air Defense System).

A detailed description of the ERINT/PAC-3 missile, which has for unknown reasons not yet received a standard missile designation (as of February 2002), is outside the scope of this article about the MIM-104.

More than 12000 MIM-104 Patriot missiles have been built so far by Raytheon, and production is continuing with the MIM-104D version.

Note: Data given by several sources show slight variations. Figures given below may therefore be inaccurate!

Data for MIM-104A/B, ERINT/PAC-3 (except where noted):

[1] Bill Gunston: "The Illustrated Encyclopedia of Rockets and Missiles", Salamander Books Ltd, 1979
[2] Hajime Ozu: "Missile 2000 - Reference Guide to World Missile Systems", Shinkigensha, 2000
[3] Bernard Blake (ed.): "Jane's Weapon Systems 1987-88", Jane's, 1988
[4] Redstone Arsenal Historical Information Website
[5] HAWK Site Denmark

Manufacturer: Raytheon. Version:

MIM-104A. IOC: 1982. Department of Defence Designation: MIM-104A. Popular Name: Patriot.

Command-guided / semi-active radar-homing. Range 160 km in PAC-1 with software changes. PAC-2 modification with bigger warhead.

Total Mass: 902 kg (1,988 lb). Core Diameter: 0.40 m (1.31 ft). Total Length: 5.34 m (17.51 ft). Span: 0.91 m (2.98 ft). Standard warhead mass: 90 kg (198 lb). Maximum range: 69 km (42 mi). Boost Propulsion: Solid rocket. Boost engine: TX-486. Guidance: Command + Inertial; Semi-active Radar Homing. Maximum speed: 3,390 kph (2,100 mph). Ceiling: 24,400 m (80,000 ft). Development Cost $: 2,210.100 million. in: 1982 average dollars. Recurring Price $: 1.367 million. Total Number Built: 6217. Flyaway Unit Cost $: 1.255 million. in: 1982 unit dollars. Version:

PAC-3. Anti-ballistic missile. Department of Defence Designation: MIM-104A.

In EMD. PAC-3 version has limited Theater Ballistic Missile Defense capability.

Historical Essay © Andreas Parsch

Lockheed Martin Patriot PAC-3

The PAC-3 (Patriot Advanced Capability 3) missile is the ATBM (Anti Theater Ballistic Missile) component of the U.S. Army's Patriot air defense system, and will complement the existing MIM-104 Patriot missiles.

The PAC (Patriot Advanced Capability) program was begun in 1986 to develop a series of significant upgrades to the Patriot system (see the MIM-104 Patriot page for general information on Patriot and more details about the PAC program). The ultimate step is PAC-3/Configuration 3, which introduces an upgraded AN/MPQ-65 radar to increase detection in high-clutter environments, and to improve discrimination of closely spaced objects (better decoy recognition). The most important feature of this new Patriot system, however, will be a completely new missile, a variant of the Lockheed Martin ERINT (Extended Range Interceptor) commonly called PAC-3 (which is a bit confusing because the earlier PAC-3 configurations systems don't use this missile). The PAC-3 missile is highly optimized for the anti-missile role (employing a hit-to-kill capability enhanced by a fragmentation warhead), so that operational PAC-3 Patriot units will be equipped eventually with both MIM-104 and PAC-3 missiles. The latter is significantly smaller than an MIM-104, so that 16 missiles instead of four can be carried in a single launch station. ERINT was first flight-tested in 1992, and selected as the ultimate PAC-3 missile in 1994. The PAC-3/ERINT integration tests took place from 1995 to 1997, and the missile is currently in LRIP (Low Rate Initial Production) status. The PAC-3 missile was also selected as the missile component of the joint US/European MEADS (Medium Extended Air Defense System).

The PAC-3 is a solid-propellant rocket-powered missile controlled by both aerodynamic fins and small forebody-mounted ACM (Attitude Control Motor) rockets for increased terminal agility. For mid-course guidance it uses essentially the same TVM (Track Via Missile) guidance as the MIM-104 Patriot, but for more accurate terminal homing, it is equipped with a Ka-Band active radar seeker. The PAC-3 missile is primarily a hit-to-kill vehicle designed to knock down incoming ballistic missiles with its kinetic energy, but it is also equipped with a high-explosive fragmentation warhead to enhance the kill probability against "conventional" targets like aircraft or cruise missiles.

The operational testing phase of the PAC-3 missile began in late 2001, and Initial Operational Capability is currently planned for 2003 (four years after the originally planned date). Although the operational tests in the first half of 2002 were only partially successful, the PAC-3 missile was declared combat-ready in August 2002. About 40 missiles have been delivered to the Army by October, and current contracts cover the production of about 120 more. In March 2003, the PAC-3 was used in combat for the first time when it intercepted Iraqi short-range SSMs during the war in the Gulf.

Designation Note: For unknown reasons, the PAC-3 has not yet received a standard missile designation (MIM-nnn) by April 2003, although it is now in operational service.

Note: Data given by several sources show slight variations. Figures given below may therefore be inaccurate!

Data for PAC-3:

[1] Hajime Ozu: "Missile 2000 - Reference Guide to World Missile Systems", Shinkigensha, 2000
[2] Lockheed Martin Missiles and Fire Control Website