MIM-104 Patriot

Four Patriot missiles like the one shown here can be fired from this mobile launcher between loadings.

The MIM-104 PATRIOT is a medium-range surface-to-air missile (SAM) system manufactured by the Raytheon Company of the United States. It replaced the Nike-Hercules Missile for high and medium altitude air defense in the US Army arsenal, and supplements the HAWK system as the US Army's low-altitude tactical mobile air defense system. The weapon became well-known during its use in the Persian Gulf War. The Patriot SAM and radar system was developed by the US Army Missile Command at Redstone Arsenal in Huntsville, Alabama, which had previously developed the Spartan and Safeguard ABM systems. Thus, the Patriot was developed upon the experience with these systems. An earlier code-name for the Patriot was the "SAM-D".

PATRIOT is the only combat-proven Tactical Ballistic Missile defense system, although the Israelli Arrow missile defense system is also operational. The latest PATRIOT PAC-3 is regarded as an advanced and successful surface-to-air missile, however combat effectiveness of earlier versions has been controversial regarding tactical ballistic missile defense. PATRIOT's radar is the world's highest performance radar system (in terms of track quality) and PATRIOT missiles can outmaneuver and intercept any current air threat. The symbol for the Patriot system is a drawing very similar to that of a New England Minuteman.

The PATRIOT is short for "Phased Array TRacking to Intercept Of Target" although this is possibly a backronym.

Introduction

The MIM-104 PATRIOT was conceived in the late 1960s as a system combining multiple new technologies, including the phased array radar and track-via-missile guidance. Full-scale development of the system began in 1976 and it was deployed in 1984, used as an anti-aircraft system. In 1988 it was upgraded to provide limited capability against anti-ballistic missile role as PAC (PATRIOT Advanced Capability). The most recent upgrade called PAC-3 is a totally new missile using the same ground equipment. PAC-3 is the first PATRIOT system designed from the outset to intercept tactical ballistic missiles.

The PATRIOT system is built around 8 combined transporter-launchers (called "Launching Stations"), each carrying 4 "certified rounds", fully contained missile cans that require no external maintenance. 8 Launching Stations are typically assigned to a Firing Battery, thus giving it a total missile inventory of 32 missiles. The newest PAC-3 upgrade is actually a totally different missile which uses some of the previous ground equipment. The PAC-3's smaller size allows for 16 missiles to be carried on each Launching Station, (4 missiles are now carried where one once was). The Launching Station is mounted on a M-860 semi-trailer, which is towed by a HEMTT. Other major system components, called the "big four", inclue the AN/MSQ-104 Engagement Control Station (ECS), mounted on a 5-ton truck or LMTV, AN/MPQ-53 Radar Set, likewise mounted on a M-860 semi-trailer and towed by a HEMTT, and the Antenna Mast Group, mounted on a 5-ton truck.

The PATRIOT system uses Track-via-Missile guidance to guide its missiles. PAC-3 has been upgraded with active radar terminal homing. Phased array radar technology is used to track targets. The electronic steering of the radar beams is critical to its functioning, as phased array systems can redirect the radar beams quickly enough to track very fast missiles, an impossible achievement with mechanically steered radar antennas.

The PAC-2 missile is 5.31 meters long, weighs 900 kg and is propelled by a solid-fueled rocket motor at speeds up to Mach 5. It is armed with a 91 kg blast-fragmentation warhead with a proximity fuze.

The PAC-3 missile is smaller, faster and (for a missile target) uses a non-explosive "hit to kill" warhead which destroys the target by collision. For slower, larger, lower-altitude targets (fighter plane, cruise missile, etc) the PAC-3 has a small explosive warhead to enhance lethality of the kinetic warhead. The PAC-3 is much more accurate than the previous Patriots, and is capable of hit-to-kill on theater ballistic missiles. The effective range is around 60 km.

Patriot systems have been sold to Israel, Germany, the Netherlands, Belgium, Japan, and Spain.

Radar

File:AN MPQ-53 radar (b030310f).jpg

A detailed view of an AN/MPQ-53 radar set

All radar functions in the PATRIOT system are concentrated in the battery-level AN/MPQ-53 radar set (unlike most SAM systems, which use separate radars, at various organizational levels, for different stages of target engagement).

The AN/MPQ-53 is a phased array, agile beam, G-band radar system providing "detection-to-kill" functioning. It can detect and track up to 100 targets, and it can command missiles going at up to 6 targets.

The agile, narrow beam characteristics of the AN/MPQ-53 radar allow it to detect small targets at long ranges. Furthermore, it is harder for RWR systems to detect a beam that hits the receiver so randomly and sporadically.

The AN/MPQ-53 set has an integrated IFF subsystem.

The AN/MPQ-65 radar set

The PAC-3 upgrade uses an improvement to the AN/MPQ-53 radar set, the AN/MPQ-65, which has better ability to discriminate real targets from decoys and to perform engagements in highly cluttered environments.

Operation

System operation, for PAC-2, in a single missile, single target scenario is as follows:

1) A target is detected by the AN/MPQ-53 radar. It identifies it by the IFF subsystem, acquires it and commences tracking of it.

2) In the AN/MSQ-104 Engagement Control Station, a computer or human operators decide to launch a missile at the target.

3) A missile is launched from one of the launchers in the battery.

4) The AN/MPQ-53 radar commences concentration of tracking energy on the target, and illuminates the target.

5) The monopulse receiver in the missile's nose receives the reflection of illumination energy from the target. It then sends data regarding it, via a downlink antenna in the missile's tail, to the AN/MPQ-53 set.

6) In the AN/MSQ-104 Engagement Control Station, computers calculate maneuvers that the missile should perform in order to maintain a trajectory to the target.

7) Guidance commands are sent via uplink antennas in the AN/MPQ-53 set to the missile, which then corrects its trajectory accordingly.

8) The missile's warhead is detonated in the vicinity of the target by a radar proximity fuze.

Usage during the 1991 Gulf War

Trial by fire

Prior to the Persian Gulf War, ballistic missile defense was an unproven concept in war. PATRIOT was assigned to shoot down incoming Iraqi Scud or Al Hussein short range ballistic missiles launched at Israel and Saudi Arabia. The first combat use of PATRIOT occurred 18 January 1991 when it successfully intercepted and destroyed an Iraqi Scud missile fired at Saudi Arabia. This was the first time an air defense system destroyed a hostile theatre ballistic missile (TBM).

Failure at Dharan

On February 25, 1991 an Iraqi Scud hit the barracks in Dharan, Saudi Arabia, killing 28 soldiers from the US Army's 14th Quartermaster Detachment.

A government investigation revealed that the failed intercept at Dharan had been caused by a software error in the system's clock. The Patriot missile battery at Dharan had been in operation for 100 hours, after which time the clock had drifted by one third of a second, equivalent to a position error of 600 meters on a target moving as quickly as an inbound TBM. The radar system detected the Scud and predicted where to look for it next, but because of the time error, looked in the wrong part of the sky and found no missile. With no missile, the initial detection was assumed to be a spurious track and the missile was removed from the system. At the time, the Israelis had already identified the problem and informed the US Army and the PATRIOT Project Office (the software manufacturer) on February 11, 1991, but no upgrade was present at the time. As a stopgap measure, the Israelis recommended rebooting the system's computers regularly, however, Army officials did not understand how often they needed to do so. The manufacturer supplied updated software to the Army on February 26; the day after the Scud struck the Army barracks.

Success rate vs. accuracy

The U.S. Army claimed an initial success rate of 80% in Saudi Arabia and 50% in Israel. Those claims were eventually scaled back to 70 and 40%. However, when President George H. W. Bush traveled to Raytheon's Patriot manufacturing plant in Andover, Massachusetts during the Gulf War, he declared, the ""Patriot is 41 for 42: 42 Scuds engaged, 41 intercepted!" [1]. The President's claimed success rate was thus over 97% during the war.

On April 7, 1992 Theodore Postol of the Massachusetts Institute of Technology, and Reuven Pedatzur of Tel Aviv University testified before a House Committee stating that, according to their independent analyses, the Patriot system had a success rate of below 10%, and perhaps even a zero success rate. In response to this testimony and other evidence, the staff of the House Government Operations Subcommittee on Legislation and National Security reported, "The Patriot missile system was not the spectacular success in the Persian Gulf War that the American public was led to believe. There is little evidence to prove that the Patriot hit more than a few Scud missiles launched by Iraq during the Gulf War, and there are some doubts about even these engagements. The public and the Congress were misled by definitive statements of success issued by administration and Raytheon representatives during and after the war." [2]

Also on April 7, 1992 Charles A. Zraket of the Kennedy School of Government, Harvard University and Peter D. Zimmerman of the Center for Strategic and International Studies testified about the calculation of success rates and accuracy in Israel and Saudi Arabia and discounted many of the statements and methodologies in Postol's report.

Success Rate – the percentage of Scuds destroyed or deflected to non-populated areas

Accuracy – the percentage of hits out of all the Patriots fired

It is important to note the difference in terms when analyzing the performance of the system during the war.

According to Zimmerman, in accordance with the standard firing doctrine on average four Patriots were launched at each incoming Scud – in Saudi an average of three Patriots were fired. If every Scud were deflected or destroyed the success rate would be 100% but the Accuracy would only be 25% and 33% respectively.

Both testimonies state that part of the problems stem from its original design as an anti-aircraft system. PATRIOT was designed with proximity fuzed warheads, which are designed to explode immediately prior to hitting a target spraying shrapnel out in a fan in front of the missile, either destroying or disabling the target. These missiles were fired at the target's center of mass. With aircraft this was fine, but considering the much higher speeds of TBMs, as well as the location of the warhead (usually in the nose), PATRIOT would most often hit closer to the tail of the Scud due to the delay present in the proximity fuzed warhead, thus not destroying the TBM's warhead and allowing it to fall to earth.

The Iraqi redesign of the Scuds also played a role. Iraq had redesigned its Soviet-style Scuds to be faster and longer ranged, but the changes weakened the missile and it was more likely to break up upon re-entering the atmosphere. This presented a larger number of targets as it was unclear which piece contained the warhead.

What all these factors mean, according to Zimmerman, is that the calculation of "Kills" becomes more difficult. Is a kill the hitting of a warhead or the hitting of a missile? If the warhead falls into the desert because a PATRIOT hit its Scud, is it a success? What if it hits a populated suburb? What if all four of the engaging PATRIOT missiles hit, but the warhead falls anyway because the Scud broke up?

According to the Zraket testimony there was a lack of high quality photographic equipment necessary to record the interceptions of targets. Therefore, PATRIOT crews recorded each launch on videotape, and damage assessment teams recorded the Scud debris that was found on the ground. Crater analysis was then used to determine if the warhead was destroyed before the debris crashed or not. Furthermore, part of the reason for the 30% improvement in success rate in Saudi Arabia compared to Israel is that the PATRIOT merely had to push the incoming Scud missiles away from military targets in the desert or disable the Scud's warhead in order to avoid casualties, while in Israel the Scuds were aimed directly at cities and civilian populations. The Saudi Government also censored any reporting of Scud damage by the Saudi press. The Israeli Government did not institute the same type of censorship. Furthermore, PATRIOT's success rate in Israel was examined by the IDF (Israel Defense Forces) who did not have a political reason to play up PATRIOT's success rate. The IDF counted any Scud that exploded on the ground (regardless of whether or not it was diverted) as a failure for the Patriot. Meanwhile, the U.S. Army who had many reasons to support a high success rate for PATRIOT, examined the performance of PATRIOT in Saudi Arabia.

A Canadian Broadcasting Corporation documentary quotes the former Israeli Defense Minister as saying the Israeli government was so dissatisfied with the performance of the missile defense, that they were preparing their own military retaliation on Iraq regardless of US objections. That response was cancelled only with the cease fire with Iraq.

Psychological effects of the system

Saddam Hussein had vowed to rain down missiles on Israel with hopes of provoking Israel to attack, thus aligning Iraq with the Arab's common cause and possibly causing those who were members of the coalition to withdraw. If this occurred the United States and its allies would lose crucial support and in Hussein's mind would not be able to continue the war.

Israel was concerned over the use of biological or chemical agents in the Scuds. The Patriot gave the Israeli government a way to calm their people in the early days of the war.

In the Iraqi bombardments on Israel two people were killed and several hundred were injured. In contrast, seven Israelis suffocated while wearing gas masks out of fear that the Scuds would be laden with chemical agents.

Patriot upgrades

As of 2002, Israel currently uses PATRIOT as part of a two-tier anti-ballistic missile defense system, with the Arrow missile in the role of high-altitude interceptor and the PATRIOT for point defense (Arrow is not yet in full operational service). PATRIOT is deployed around Israel's nuclear reactor and nuclear weapons assembly point at Dimona.

Later upgrades include the PAC-2 or PATRIOT ADVANCED CAPABILITY 2. It too is a proximity fuzed weapon, but it features numerous performance upgrades over Standard and PAC-1 missiles, including a new proximity device with a shorter fuze, which helps to curtail the problems arising from the speed of TBMs.

The GEM (guidance enhanced missile) is an addition to the PAC-2 that upgrades the speed at which the missile communicates with the ECS, thus allowing more of a chance for the missile to correct itself in-flight. It also provides the missile itself with a small computer, allowing it to compute certain interception algorithms which would otherwise have to be sent from the ECS.

The PAC-3 missile is a totally new and different design from previous PATRIOT missiles. It is smaller than the earlier PATRIOT rounds, and is more accurate due to its high maneuverability and use of terminal Active radar homing. This means the missile contains a fully functional radar which can detect the target at short ranges (during the terminal phase of flight) and make trajectory corrections immediately before impact. Thus, PAC-3 is a hit-to-kill missile which can specifically target the warhead of an inbound TBM. It contains only a small amount of explosive, and relies on its kinetic energy to destroy the incoming warhead. Because of the reduced size, a launcher trailer can carry sixteen PAC-3 missiles (four canisters with four missiles per canister) rather than the four missiles carried by the PAC-1 or PAC-2 trailers (four canisters with one missile per canister). However, some believe the PAC-3 is less effective against fixed-wing aircraft and cruise missiles due to its smaller size and smaller explosive warhead. The PAC-3 missile system has about seven times the area coverage of the original Patriot missile system. [3]

Many improvements have been made to the Patriot's software. Raytheon has created a software only upgrade that allows the PAC-1 to target incoming MLRS attacks. This was done primarily as a counter to North Korea's heavy build-up of the MLRS capable units. Secondly it gives both the military and Raytheon a marketing tool to sell the system and stockpiled PAC-1s (left over from the Iraq Containment Operations in Saudi Arabia and Kuwait from 1991 to 2003) to South Korea. By 2012, Medium Extended Air Defense System (MEADS) will replace Patriot in the US Army and NATO.

Usage during Operation "Iraqi Freedom" of 2003

OIF was described as "a substantial success" for PATRIOT in the report to the Defense Science Task Force. PATRIOT batteries had at least eight independently confirmed TBM kills during the campaign, and PATRIOT batteries themselves reported successfully shooting down all eleven Iraqi TBMs that threatened coalition assets, including one TBM that would have struck a high-level command group location. Echo Battery, 2nd Battalion, 43rd Air Defense Artillery fired and successfully engaged with the first PAC-3 missiles in combat. PATRIOT also provided radar surveillance for coalition assets who lacked a clear picture over much of Iraq.

PATRIOT PAC-3 had a very high sucess rate intercepting Al Samoud-2 and Ababil-100 tactical ballistic missiles during operation Iraqi Freedom[4]. However no longer-range Scud missiles were fired during that conflict. One CSSC-3 "Seersucker" sea-skimming cruise missile was not intercepted, but it was outside PATRIOT radar range so it was never attempted. The missile struck a seawall in Kuwait City, doing minimal damage.

PATRIOT had two fratricides in Iraq, one against a British RAF Tornado GR4A, the other against an F/A-18 Hornet. The Tornado was engaged because the system mistakenly classified it as an anti-radiation missile (ARM). This was a result of mistakes on many different levels. First, the Tornado was inbound for landing at the time of the incident, which took it directly over the PATRIOT firing battery. Second, RAYTHEON PATRIOT planners had made the parameters by which the system classifies ARMs too wide, which allowed for a track appearing like the Tornado to be classified as an ARM by the system. Third, and probably most significantly, the Tornado did not have its IFF transponder on, which could have been an instant indication of the misclassification.

The other fratricide, on an F/A-18 Hornet, was a PATRIOT system error resulting from a misclassified TBM. The system engaged the Hornet automatically after the software, in conjunction with the PATRIOT radar, incorrectly classified the aircraft as a TBM. The PATRIOT system software classified the F/A-18 Hornet as a TBM, and its flight path showed it inbound to the Karbala Gap region. The aircraft was engaged by the PAC-III PATRIOT missile shortly after the launching stations were brought into operation. The aircraft that was flying with the F/A-18 Hornet was almost engaged by a rear PATRIOT unit as well, until the order was given to disregard.

A third Blue-on-blue incident occurred when a USAF F-16 Falcon incorrectly identified a PATRIOT battery as an SA-2 battery, after the battery's radar signature was detected by the F-16. At the time, the PATRIOT battery was protecting the 101st Airborne Division's Headquarters near the Forward Line of Troops (FLOT). The F-16 fired an AGM-88 HARM missile, which struck directly in front of the PATRIOT Radar Set, rendering it non-mission capable. The affected PATRIOT unit was forced to swap its radar set with another unit's in the immediate area; it must be noted that the replacement radar set had not fully undergone a testing period after receiving its PAC-3 upgrade/enhancements. The same battery was later responsible for the fratricide of the F/A-18 mentioned above.

Operation Iraqi Freedom marks the first use of PATRIOT to manuever with and cover the forward combat elements in a large operation - previously, it had been thought that the system was too large to be quickly redeployed, and its use was restricted to defending primarily stationary assets. Tactics were refined during the years between Desert Storm and Opperation Iraqi Freedom, and several PATRIOT batteries successfully managed to protect the airspace above the forward push towards Baghdad in the first weeks of the war.

External links and references