MIM-104 Patriot

Competitors:
SA-20 GARGOYLE / S300PMU/2/3  Compare
SA-12 Gladiator/Giant S300V  Compare
SA-21 GROWLER / S400 Triumph Long Range TABM/SAM  Compare

PAC- 1 PAC- 2 PAC- 3
MIM-104A MIM-104C PAC- 3
Type Land-mobile, surface-
to-air guided weapon system Single-stage,
low-to-high-altitude Single-stage, short-range, low-to high-altitude
Launcher four-round
Mobile trainable semi-trailer eight-round
Mobile trainable semi-trailer
Manufacturer Raytheon Raytheon (Prime contractor), Lockheed, Siemens, Mitsubishi. Lockheed Martin Vought Systems
Status Not in production In production In production
Length 5.3m 5.18m 5.2m
Diameter 41cm 41cm 25cm
Wingspan 92cm 50cm
Fins four delta shaped fins
Launch Weight 914 kg 900kg 312kg
Propulsion Single-stage solid
propellant rocket motor Single-stage solid
propellant rocket motor Single-stage solid
propellant rocket motor with special attitude-control mechanism for in-flight maneuvering
Guidance Command guidance and semi-active homing, track-via-missile (TVM) Command guidance with TVM and semi-active homing Inertial/Active
millimeter-wave radar
terminal homing
Warhead HE
single 90 kg 91kg HE blast/
fragmentation with proximity fuze hit-to-kill +
lethality enhancer
73 kg HE blast/fragmentation
with proximity fuze]
Max speed Supersonic
(in excess of Mach 3) Mach 5 Mach 5
Time of flight minimum nine seconds
maximum three and a half minutes

Min altitude 60 meters
Max attitude NA 24 km 10-15 km
Min range NA 3 km --
Max range - anti-air 70 km 160 km 15 km
Max range - anti-missile 15-45 km

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.

Major Components

1. Phased array radar. It's beam is electronically aimed at a different piece of the sky every few microseconds. No moving parts. Extremely difficult to jam.

2. Engagement Control Station (ECS). Where the computer and the operators fight the air battle. Man-machine interaction options here can range from letting the computer assist in target identification and prioritization to leaving the ECS and letting the computer fight the entire air battle itself.

3. 6 to 8 missile launchers. Missiles come factory packed in containers which are loaded directly onto the launcher. The Launcher can be located up to 1 kilometer away from the ECS/Radar, receiving commands automatically via microwave data link.

4. Patriot missile. Achieves supersonic speed within 20ft of leaving the launcher. Range: 100+ km. It can outmaneuver any manned aircraft and most missiles. It is controlled in flight automatically by the computer.

Patriot-unique equipment at the Headquarters and Headquarters Battery (HHB) includes the information and coordination central (ICC), communications relay groups (CRGs), antenna mast groups (AMGs), trailer mounted electric power units (EPUs), and guided missile transporters (GMT). The Patriot firing battery equipment includes the AMG, radar set (RS), engagement control station (ECS), truck mounted electric power plant (EPP), and up to sixteen launching stations (LSs). Both the battalion and firing batteries are equipped with a semitrailer maintenance center.

(1) The ICC is manned during air battle operations and provides necessary command and control links to interface with higher echelon, lateral and subordinate battalions, and its own firing units.

(2) The ECS is the only manned station in the battery during the air battle and is the operations control center of the Patriot battery. The ECS contains the weapons control computer (WCC), man/machine interface and various data and communication terminals. Its prime mover is a 5-ton tactical cargo truck.

(3) The RS is a multifunction, phased-array radar mounted on an M860 semitrailer. The prime mover is an M983 10-ton heavy expanded mobility tactical truck (HEMTT) tractor.

(4) The LS is a remotely operated, fully self-contained unit, carrying integral on-board power. The launcher is mounted on an M860 semitrailer towed by a M983 HEMTT 10-ton tractor. Each LS may be loaded with four PAC-2 missile rounds (MRs), or 16 PAC-3 missile rounds if the LS is PAC-3 modified. The MR consists of a Patriot missile mounted within a sealed aluminum canister that functions both as a shipping and storage container and as a launch tube. Canisters are either single or 4-packs and are mounted two by two on the launcher.

(5) The CRG provides a multi-routed, secure, two-way data relay capability between the ICC and its assigned fire units and adjacent units. The CRG also provides the capability for both data and voice exit and entry point communications with elements external to the Patriot ADA battalion.

(6) The AMG consists of four ultra high frequency (UHF) antennas used for communications between the ICC, CRG, ECS and adjacent units and or higher echelons. The AMG can be remotely controlled in azimuth from within the ECS.

(7) The EPP consists of two 150-kw generator sets, a power distribution unit (PDU), cables, and accessories mounted on a modified HEMTT. The PDU is stored between the generators and contains a parallel powerbus and power contractors to supply prime power to the ECS and RS.

The MIM-104A 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. The Patriot missile is inertially guided with command updates, using TVM for high terminal accuracy. 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 the new GEM+ version, and many existing PAC-2 rounds (MIM-104C/D) will be upgraded to MIM-104E standard by replacement of the missile forebody. The upgrade consists of a new low-noise front end to increase seeker sensitivity (improving acquisition and tracking of small RCS targets) and a modernized fuzing system for better performance against ballistic missile targets. Reliability of the GEM+ missile is also improved by replacement of older components with new technology. The first MIM-104Es were delivered to the U.S. Army in November 2002.

The PAC-3 system incorporates many changes to the ground equipment 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 upgrades to the radar (now designated AN/MPQ-65) 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). It is commonly called PAC-3 (q.v. for further details), which is a bit confusing because the interim PAC-3 systems don't use this missile.

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

Testing of Patriot's response to a unique, advanced electronic countermeasure (ECM) technique exposed an air defense system weakness and recommended corrective measurees. Over 155 Patriot surveillance investigations and 6 missile firings were completed in extensive ECM environments consisting of stand-off jamming, selfscreening jamming, and chaff.

The AN/MPQ-53 is a frequency-agile multifunction G/H- Band radar group which performs surveillance, Identification Friend-or-Foe (IFF), tracking and guidance, and Electronic Counter Measures (ECM) functions entailed in the Patriot tactical air defence missile system. The antenna array is a 2.44 m diameter, 5,161-element phased-array planar configuration carried on a semi-trailer chassis. The antenna unit has separate arrays for target detection and tracking, missile guidance and IFF functions. The last of these tasks is carried out by an AN/TPX-46(V)7 interrogator, using a supplementary array adjacent the main circular search and track array on the antenna unit. Other supplementary arrays are for sidelobe cancellation and missile guidance signal reception.

The interrogator set AN/TPX-46(V)7 consists of the central processing/receiver-transmitter chassis and Mode 4 control panel chassis which accomodates interrogator computer KIR-1A/TSEC. Contractor designed antenna is integral to radar set face (LIN r18815, BOIP 770208). The IFF is designed for automatic operation under control of the engagement control station (ECS) weapon control computer. The Interrogator Set Mark XII/SIF equipment utilizes AN/TPX-46(V)7 technology for dedicated application to the Patriot system. The IFF provides a rapid secure means of identifying suitably equipped friendly aircraft, and thereby avoid their destruction by friendly fire. It is employed by Patriot fire unit, and is controlled and monitored by the engagement control station (ECS).

PATRIOT battalions with PAC-3 fire units were employed in Operation Iraqi Freedom (OIF) against TBMs. In OIF, PAC-3 interceptors were ripple-fired against ballistic missile threats, a user requirement that was not demonstrated during operational testing. This eliminated the need for a follow-on test to demonstrate this capability. All PATRIOT engagements were conducted in a complex operational environment. There were three instances of erroneous engagements between PATRIOT batteries and friendly aircraft. System performance against TBMs appears to have been highly effective and consistent with expectations documented in DOT&E’s beyond low-rate initial production report submitted to Congress in October 2002. PATRIOT performance during OIF is detailed in the classified FY03 BMDS annual report.

In November 2004 there were no major issues during the Patriot PAC-3 Missile Segment Enhancement preliminary design review, which will be followed by one more review, the critical design review, in late summer 2005.