MIM-104 Patriot, US Surface to Air Missile

The MIM-104 Patriot is a surface-to-air missile (SAM) system, the primary of its kind used by the United States Army and several allied nations. It is manufactured by the Raytheon Company of the United States. The Patriot System replaced the Nike Hercules system as the U.S. Army's primary High to Medium Air Defense (HIMAD) system, and replaced the MIM-23 Hawk system as the U.S. Army's medium tactical air defense system. In addition to these roles, Patriot has been given the function of the U.S. Army's anti-ballistic missile (ABM) system, which is now Patriot's primary mission.

MIM-104 Patriot uses an advanced aerial interceptor missile and high performance radar systems. Patriot was developed at Redstone Arsenal in Huntsville, Alabama, which had previously developed the Safeguard ABM system and its component Spartan and Sprint missiles. The symbol for Patriot is a drawing of a Revolutionary War-era Minuteman.

MIM-104 Patriot systems have been sold to Taiwan, Egypt, Germany, Greece, Israel, Japan, Kuwait, the Netherlands, Saudi Arabia, United Arab Emirates, and Spain. Poland hosts a battery of Patriot launchers in Morąg since 24 May 2010. The system will be integrated into the Polish air defence system until 2012. The Republic of Korea is also in the process of purchasing several second-hand Patriot systems after North Korea test-launched ballistic missiles to the Sea of Japan and proceeded with underground nuclear testing in 2006.

Patriot missile
Type	Surface-to-air missile
Place of origin	United States
Production history
Designer	Raytheon
Unit cost	US$ 1 to 6 million
Number built	over 8,600
Variants	Standard, ASOJ/SOJC, PAC-2, PAC-2 GEM, GEM/C, GEM/T (or GEM+) and PAC-3
Specifications (PAC-1)
Weight	700 kg
Length	5,800 mm
Diameter	410 mm
Warhead	M248 Composition B HE blast/fragmentation with two layers of pre-formed fragments and Octol 75/25 HE blast/fragmentation
Warhead weight	200 lb (90 kg)
Detonation mechanism	Proximity fuze
Wingspan	920 mm (3 ft 0 in)
Propellant	Solid-fuel rocket
Operational range	PAC - 1 :70 km PAC - 2 :70-160 km PAC - 3 :15 km
Flight altitude	79,500 feet (24,200 m)
Speed	Mach 5.0
Guidance system	Radio command with Track Via Missile semi-active homing
Launch platform	mobile trainable four-round semi-trailer

MIM-104 Patriot equipment

The Patriot system has four major operational functions: communications, command and control, radar surveillance, and missile guidance. The four functions combine to provide a coordinated, secure, integrated, mobile air defense system.

The Patriot system is modular and highly mobile. A battery-sized element can be emplaced in less than 1 hour. All components, consisting of the fire control section (radar set, engagement control section, antenna mast group, electric power plant) and launchers, are truck- or trailer-mounted. The radar set and launchers (with missiles) are mounted on M860 semi-trailers, which are towed by M983 HEMTTs.

Missile reload is accomplished using an M985E1 truck with a crane on the back. This crane is bigger than the standard crane found on most HEMTTs. This crane, called a Guided Missile Transporter (GMT), removes spent missile canisters from the launcher and then replaces them with fresh missiles. Because the crane nearly doubles the height of the HEMMT when not stowed, crews informally refer to it as the "scorpion tail." A standard M983 with a regular-sized crane is referred to as the Large Repair Parts Transporter (LRPT).

The heart of the Patriot battery is the fire control section, consisting of the AN/MPQ-53 or -65 Radar Set, the AN/MSQ-104 Engagement Control Station (ECS), the OE-349 Antenna Mast Group (AMG), and the EPP-III Electric Power Plant. The system's missiles are transported on and launched from the M901 Launching Station, which can carry up to four PAC-2 missiles or up to sixteen PAC-3 missiles. A Patriot battalion is also equipped with the Information Coordination Central (ICC), a command station designed to coordinate the launches of a battalion and uplink Patriot to the JTIDS or MIDS network.

The AN/MPQ-53 and AN/MPQ-65 Radar Set

The AN/MPQ-53/65 Radar Set is a passive electronically scanned array radar equipped with IFF, electronic counter-countermeasure (ECCM), and track-via-missile (TVM) guidance subsystems.

The AN/MPQ-53 Radar Set equips PAC-2 units, while the AN/MPQ-65 Radar Set equips PAC-3 units. The main difference between these two radars is the addition of a second traveling wave tube (TWT), which gives the -65 radar increased search, detection, and tracking capability. The radar's antenna array consists of over 5,000 elements that "flash" the radar's beam many times per second. Additionally, the radar's antenna array contains an IFF interrogator subsystem, a TVM array, and at least one "sidelobe canceller" (SLC), which is a small array designed to decrease interference that might affect the radar. Patriot's radar is somewhat unique in that it is a "detection-to-kill" system, meaning that a single unit performs all search, identification, track, and engagement functions. This is in contrast to most SAM systems, where several different radars are necessary to perform all functions necessary to detect and engage targets.

The beam created by the Patriot's flat phased array radar is comparatively narrow and highly agile compared to a moving dish. This gives the radar an unmatched ability to detect small, fast targets like ballistic missiles, or low radar cross section targets such as stealth aircraft or cruise missiles. Additionally, the power and agility of Patriot's radar is highly resistant to countermeasures, including electronic countermeasures (ECM) radar jamming and radar warning receiver (RWR) equipment. Patriot is capable of quickly jumping between frequencies to resist jamming.

The AN/MSQ-104 Engagement Control Station

The AN/MSQ-104 Engagement Control Station (ECS) is the nerve center of the Patriot firing battery. The ECS consists of a shelter mounted on the bed of an M927 5-Ton Cargo Truck or on the bed of a Light Medium Tactical Vehicle (LMTV) cargo truck. The main sub-components of the ECS are the Weapons Control Computer (WCC), the Data Link Terminal (DLT), the UHF communications array, the Routing Logic Radio Interface Unit (RLRIU), and the two manstations that serve as the system's man-to-machine interface. The ECS is air conditioned, pressurized (to resist chemical/biological attack), and shielded against electromagnetic pulse (EMP) or other such electromagnetic interference. The ECS also contains several SINCGARS radios to facilitate voice communications.

The WCC is the main computer within the Patriot system. It is a 24-bit parallel militarized computer with fixed and floating point capability. It is organized in a multiprocessor configuration that operates at a maximum clock rate of 6 megahertz. This computer controls the operator interface, calculates missile intercept algorithms, and provides limited fault diagnostics. Compared to modern personal computers, it has somewhat limited processing power, although it has been upgraded several times during Patriot's service life.

The DLT connects the ECS to Patriot's Launching Stations. It uses either a SINCGARS radio or fiber optic cables to transmit encrypted data between the ECS and the launchers. Through the DLT, the system operators can remotely emplace, slew or stow launchers, perform diagnostics on launchers or missiles, and fire missiles.

The UHF communications array consists of three UHF radio "stacks" and their associated patching and encrypting equipment. These radios are connected to the antennas of the OE-349 Antenna Mast Group, which are used to create UHF "shots" between sister Patriot batteries and their associated ICC. This creates a secure, real-time data network (known as PADIL, Patriot Data Information Link) that allows the ICC to centralize control of its subordinate firing batteries.

The RLRIU functions as the primary router for all data coming into the ECS. The RLRIU gives a firing battery an address on the battalion data network, and sends/receives data from across the battalion. It also "translates" data coming from the WCC to the DLT, facilitating communication with the launchers.

Patriot's crew stations are referred to as Manstation 1 and 3 (MS1 and MS3). These are the stations where Patriot operators interface with the system. The manstations consist of a monochrome (green and black) screen surrounded by various Switch Indicators. Each manstation also has a traditional QWERTY keyboard and isometric stick, a tiny joystick that functions much like a PC mouse. It is through these switch indicators and the Patriot user interface software that the system is operated.

The OE-349 Antenna Mast Group

The OE-349 Antenna Mast Group (AMG) is mounted on an M927 5-Ton Cargo Truck. It includes four 4 kW antennas in two pairs on remotely controlled masts. The antennas can be controlled in azimuth, and the masts can be elevated up to 100 feet 11 inches (30.76 m) above ground level. Mounted at the base of each pair of antennas are two high-power amplifiers associated with the antennas and the radios in the collocated shelter. It is through these antennas that the ECS and ICC send their respective UHF "shots" to create the PADIL network.

The EPP-III Electric Power Plant

The EPP-III Diesel- Electric Power Plant (EPP) is the power source for the ECS and Radar. The EPP consists of two 150 kilowatt diesel turbine engines(the same turbines that power Apache helicopters) with 400 hertz generators that are interconnected through the power distribution unit. The generators are mounted on a modified M977 HEMTT. Each EPP has two 75-gallon (280 L) fuel tanks and a fuel distribution assembly with grounding equipment. Each diesel engine can operate more than 8 hours with a full fuel tank. The EPP delivers its power to the Radar and ECS through cables stored in reels alongside the generators.

The M901 Launching Station

The M901 Launching Stations are remotely-operated, self-contained units. The ECS controls operation of the launchers through each launcher's DLT, via fiber optic or VHF (SINCGARS) data link.

Integral leveling equipment permits emplacement on slopes of up to 10 degrees. Each launcher is trainable in azimuth and elevates to a fixed, elevated launch position. Precise aiming of the launcher before launch is not necessary; thus, no extra lags are introduced into system reaction time. Each launcher is also capable of providing detailed diagnostics to the ECS via the data link.

The launching station contains four major equipment subsystems: the launcher generator set, the launcher electronics module (LEM), the launcher mechanics assembly (LMA), and the launcher interconnection group (LIG). The generator set consists of a 15 kW, 400 Hz generator that powers the launcher. The LEM is used for the real-time implementation of launcher operations requested via data link from the ECS. The LMA physically erects and rotates the launcher's platform and its missiles. The LIG connects the missiles themselves to the launcher via the Launcher Missile Round Distributor (LMRD).

MIM-104 Patriot Guided Missile

The first fielded variant was the round MIM-104A, "Standard." It was optimized solely for engagements against aircraft and had very limited capability against ballistic missiles. It had a range of 70 km (44 miles), and a speed in excess of Mach 3. The MIM-104B "anti-standoff jammer" (ASOJ) is a missile designed to seek out and destroy ECM emitters.

The MIM-104C PAC-2 missile was the first Patriot missile that was optimized for ballistic missile engagements. The GEM series of missiles (MIM-104D/E) are further refinements of the PAC-2 missile. The PAC-3 missile is a new interceptor, featuring a Ka band active radar seeker, employing "hit-to-kill" interception (in contrast to previous interceptors' method of exploding in the vicinity of the target, destroying it with shrapnel), and several other enhancements which dramatically increase its lethality against ballistic missiles. It has a substantially lower range of 15 km. The specific information for these different kinds of missiles are discussed in the "Upgrades" section.

The first seven of these are in the larger PAC-2 configuration of a single missile per canister, of which four can be placed on a launcher. PAC-3 missile canisters contain four missiles, so that sixteen rounds can be placed on a launcher. The missile canister serves as both the shipping and storage container and the launch tube. Patriot missiles are referred to as "certified rounds" as they leave the factory, and additional maintenance is not necessary on the missile prior to its being launched.

The PAC-2 missile is 5.8 metres (19 ft 0 in) long, weighs about 900 kilograms (2,000 lb), and is propelled by a solid-fueled rocket motor at speeds in excess of Mach 5.0.

MIM-104 Patriot missile design

The PAC-2 family of missiles all have a fairly standard design, the only differences between the variants being certain internal components. They consist of (from front to rear) the radome, guidance section, warhead section, propulsion section, and control actuator section.

The radome is made of slip-cast fused silica approximately 16.5 millimetres (0.65 in) thick, with nickel alloy tip, and a composite base attachment ring bonded to the slip cast fused silica and protected by a molded silicone rubber ring. The radome provides an aerodynamic shape for the missile and microwave window and thermal protection for the RF seeker and electronic components.

The Patriot guidance section consists primarily of the modular digital airborne guidance system (MDAGS). The MDAGS consists of a modular midcourse package that performs all of the required guidance functions from launch through midcourse and a terminal guidance section. The TVM seeker is mounted on the guidance section, extending into the radome. The seeker consists of an antenna mounted on an inertial platform, antenna control electronics, a receiver, and a transmitter. The Modular Midcourse Package (MMP), which is located in the forward portion of the warhead section, consists of the navigational electronics and a missile-borne computer that computes the guidance and autopilot algorithms and provides steering commands according to a resident computer program.

The warhead section, just aft of the guidance section, contains the proximity fused warhead, safety-and-arming device, fuzing circuits and antennas, link antenna switching circuits, auxiliary electronics, inertial sensor assembly, and signal data converter.

The propulsion section consists of the rocket motor, external heat shield, and two external conduits. The rocket motor includes the case, nozzle assembly, propellant, liner and insulation, pyrogen igniter, and propulsion arming and firing unit. The casing of the motor is an integral structural element of the missile airframe. It contains a conventional, casebonded solid rocket propellant.

The Control Actuator Section (CAS) is at the aft end of the missile. It receives commands from the missile autopilot and positions the fins. The missile fins steer and stabilize the missile in flight. A fin servo system positions the fins. The fin servo system consists of hydraulic actuators and valves and an electrohydraulic power supply. The electrohydraulic power consists of battery, motor pump, oil reservoir, gas pressure bottle, and accumulator.