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Patriot Missile Failure, Gulf War

Benji Boban

SYSM 6309: Advanced Requirements EngineeringSpring 2012

2/25/2012

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Table of Contents1. Patriot Missile System – Description

2. Use in the Gulf War

3. Failures of the Patriot Missile System

4. Cause of the Failure

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Patriot Missile System• “Phased Array Tracking Radar to Intercept on Target” or

“Patriot” • Its initial purpose was as an anti-aircraft system, but it

quickly became used as anti-tactile ballistic missiles. • The Patriot Missile system consists of an advanced

radar system and an anti-ballistic missile.• The system consists of 4 functions:

– Communications,

– Command and Control,

– Radar surveillance

– Missile guidance.

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Patriot Missile System, cont..• AN/MPQ -53 or 65 radar set

– Consists of a • scanned array radar with Identification Friend or Foe technology

• Electronic Counter Countermeasure (ECCM)

• TVM (Track Via Missile) guidance system

– The AN/MPQ is a singe unit, as opposed to multiple radars for the system. Basically it is the only array used from missile detection to the missile engagement/destruction.

• AN/MSQ-104 engagement control station– Consists of

• Weapons control computer (WCC) - The computer of the patriot missile systems

• Data Link Terminal – The interface to the missile launchers

• UHF communications array – Creates the medium for network communications between the patriot missile systems

• RLRIU (Routing Logic Radio Interface Unit) – Router for all the data traffic of the patriot system

• Two computer manstations - stations where humans (operators) interface with the system

– It is contained in a mobile shelter capable of withstanding Electromagnetic Interference, chemical/biological attacks, and also acts as protection against the elements.

http://en.wikipedia.org/wiki/MIM-104_Patriot#cite_note-DACS_Working_Paper-12

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Patriot Missile System cont…• OE-349 Antenna Mast Group

– Consists of a • mobile platform• 4 antennas in two pairs with it’s associated amplifiers and radios.

– It is used to create the patriot communications network.

• M901 Launching Station– Launching stations which contain the missile and the launchers– Remotely controlled– Self contained

• Patriot Missile– MIM-104A – solely for anti-aircraft purpose– MIM104C/D/E (PAC-2) - for anti-missile; intended to explode on engagement

• Version MIM104C was used in the Gulf War

– MIM104F (PAC-3) – latest version; hit to engage– They consist of 4 sections

• Radome – the tip of the missile, contains the window and protection for the RF seeker

• Guidance section – Consists of the auto-guidance systems and also the Track via guidance System (from ground control)

• Warhead section

• Propulsion section

• Control actuator section – controls the fins of the missile for stability and steering

http://en.wikipedia.org/wiki/MIM-104_Patriot#cite_note-DACS_Working_Paper-12

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Use in the Gulf War• The Persian Gulf War was the first usage of the Patriot missile

system to shoot down ballistic missiles as opposed to only aircraft.• It was used 40 times to shoot down missiles, primarily Scud or Al

Hussein short range ballistic missiles.• The first engagement, which was initially reported as successful,

occurred on January 18, 1991.• Two camps debated the success of the program

– Theodore Postol of MIT and Reuven Pedatzur of Tel Aviv University stated less then 10% success rate conducted via video tape analysis

– Charles A Zraket of Harvard University and Peter D. Zimmerman of the Center for Strategic and International Studies debated the calculation method of the success rate and accuracy.

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Failures of the Patriot Missile Systems

• The initial launch was actually a computer glitch

• The worst failure was when an army barracks in Dhahran, Saudi Arabia was hit by a Scud missile and 28 people died.

• There was a difference between the calculation of the success rate between Saudi Arabian setups and the Israeli setups.– The Saudi Arabian setups considered

deflections as success– The Israel setups, due to the targets

being civilian areas, considered only annihilation of the missile as success.

http://www.sitesatlas.com/Maps/Maps/604.htm

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Cause of Failure• The generally accepted conclusion is a software based round-off error occurred

causing the failure• The WCC was a 24bit machine. • The algorithm used to calculate the path of the Scud Missile was called the Range-

Gate Algorithm.• Velocity and time are the two variables need to calculate the position of the missile.

The current time of the system was recorded in tenths of a second in whole integers. The velocity was also stored.

• However since it was only 24bit machine, there was a loss in precision as the time increased or the velocity has significantly higher.

• The WCC uses the Range-Gate output to calculate the location of the Scud. If the Scud is not in the location determined by the output, then it is deemed to not be a Scud and therefore not a threat.

• The System had been on for over 100 hours and therefore the Range-Gate algorithm was significantly off and no missile was detected in the Dhahran attack.

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Cause of Failure cont…

([2], Page 7)

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Reason of the Cause of Failure

• Requirements:– How was success defined? In the requirements?

• Does success imply destruction of warhead, engagement of the material, or even deflection of the warhead?

– How is Accuracy defined?• If three Patriot missiles are fired at one Scud; how would the accuracy be defined?

• Testing– Was there a way to test the drift of the system?

• The agility of the upgrade– It was rumored the fix upgrade was available, but did not arrive until the day

after the fatal attack at Dhahran.

• Was the System used out of specifications?– Considered a mobile unit. Should not be running for long periods of time.

• Using Outdated equipment?– The equipment was designed from the 1970’s, i.e. 24bit computer.

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Bibliography

[1] MIM-104 Patriot ://en.wikipedia.org/wiki/MIM-104_Patriot#Patriot_in_the_Persian_Gulf_War.2FOperation_Desert_Storm_.28January-February_1991.29

[2] Patriot Missile Defense: Software Problem Led to System Failure at Dhahran, Saudi Arabia, GAO/IMTEC-92-26 Patriot Missile Software Problem, http://www.gao.gov/assets/220/215614.pdf (February 1992)

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Questions