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Patriot Missile Failure

Benji Boban

SYSM 6309: Advanced Requirements EngineeringSpring 2012

5/19/2012

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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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Reason of the Cause of Failure• First step to resolving any problem is to clearly

define the problem– As we are looking at the problem in Hindsight, it is relatively easy

• Problem Statement: “System failed to identify a enemy missile after the system had been running continuously for over 100 hours”

• If we assume the Patriot Missile Systems was correctly working on the European War front prior to the Persian Gulf War, then these problems can be considered as requirements creep.

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Problems4 major areas in which there were problems:

1. Domain/Environment Change2. Software

1. Software clock drift/Round-off error2. Reboot time3. Software delivery time 4. Software upgrade time

3. Hardware1. No Recorder2. Difference in Ballistic Missiles versus Aircraft/Cruise Missiles

4. User Ware1. No Auditory Alarms2. Information on Operation doctrine

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Domain/Environment Change• Environment change – Changes were accounted for during the conflict. “As

information from all sources became available, software changes were made from August 1990 to February 199 1 by the Patriot Project Office in Huntsville, Alabama, to adapt the system to the Desert Storm environment.” [1]

• The major change needed was the reduction of the dependence of the system to its mobile characteristic. “The Patriot system was originally designed to operate in Europe against Soviet medium- to high-altitude aircraft and cruise missiles…To avoid detection it was designed to be mobile and operate for only a few hours at one location.” [1] – THIS IS A SIGNIFICANT REQUIREMENTS CREEP.

http://www.probertencyclopaedia.com/photolib/maps/Map%20of%20Soviet-Finnish%20Front%20During%20Second%20World%20War%201945.htm

http://images.suite101.com/736632_com_mapdeserts.png

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Software1. Software clock drift/Round-off error – Root Cause2. Reboot time3. Software delivery time 4. Software upgrade time

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Software cont…• The generally Root Cause Analysis conclusion is a software based round-off error

occurred causing the failure• The algorithm used to calculate the path of the Scud Missile was called the Range-

Gate Algorithm.• However since it was only 24bit machine, there was a loss in precision as the time

increased or the velocity has significantly higher.• 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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Software cont…• Reboot time to reset the clock

– At the beginning of the War, only about a two minute window to actually detect and track the missile. A reboot took 1.5 to 2 minutes, therefore a chance to miss an incoming missile.

• Software delivery time– The upgrade patch took 10 days to reach onsite.

• Software upgrade time– 1 – 2 hours of downtime. If I was a captain on the front lines, this would

be very dangerous.

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Hardware• Missile Requirements

– Went from Mach 2 to Mach 5– Solved via Software upgrade. Establishes presence of some

form of feedback loop.

• Recorder– Not a requirement in the initial build.– External recorders available, but Army officials did not want use

it because of worry of causing system failures. However, Israeli’s used one and found the problem a lot sooner (14 days before the disaster)

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User• Audible Alarm

– The operators had to stare at the DCC, no audible alarm to inform them of an incoming missile.

– This may/may not have affected the above described problem, but does show a lack of end level user feedback/resolution

• Operation Doctrine not explained to operators– “The Patriot system was originally designed to operate in Europe

against Soviet medium- to high-altitude aircraft and cruise missiles…To avoid detection it was designed to be mobile and operate for only a few hours at one location.” [3]

– If this was explained to operators, then they may have been more amiable to looking of problems.

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User• Operation Doctrine not explained to operators

– “The Patriot system was originally designed to operate in Europe against Soviet medium- to high-altitude aircraft and cruise missiles…To avoid detection it was designed to be mobile and operate for only a few hours at one location.” [3]

– If this was explained to operators, then they may have been more amiable to looking of problems.

• Communications process were broken down– Two main areas:

1. Field Users to Army Officals• When the Patriot Office told the Army, extended use can cause miscalculations, they

ignored the memo and did not tell the field users because they thought the Patriot System was still being used as a mobile system. [2]

2. Israeli Army to US Army Officials• The US Army described the Israeli use as atypical [2]

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User cont…

Patriot Missile System

Operator

US Army Officials

Israeli ArmyOfficials

Communications process were broken downTwo main areas:

1. Field Users to Army Officals• When the Patriot Office told the Army, extended use can cause miscalculations, they ignored the

memo and did not tell the field users because they thought the Patriot System was still being used as a mobile system. [2]

2. Israeli Army to US Army Officials• The US Army described the Israeli use as atypical [2]

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Life Cyclehttp://www.utdallas.edu/~chung/SYSM6309/process.pdf Page 9

• It was obvious, the army and the contractor had gone through a few cycles of this, i.e. 6 software updates during the war• However, if just one more round had occurred faster with the information of the system being used to guard barracks, then the problem may have been avoided.

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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