Chapter VII : Case Study # 3 : Patriot Missile Failure

1.)With the benefit of hindsight, what steps could have been taken during development of the Patriot software to avoid the problems that led to the loss of life? Do you think these steps would have improved the Patriot's effectivenessenought to make it obvious taht the missile was a strong deterrent against the Scud? Why or why not?

The Patriot is a surface-to-air defence missile system manufactured by Raytheon³ and used by the United States Army, originally designed to protect against Soviet cruise missiles and medium to high altitude aircraft. In order to avoid detection it was mobile and would only operate for a few hours at a time.

During Operation Desert Shield (the operation to move forces to the Gulf region), Patriot battalions were deployed in strategic locations in Saudi Arabia and Israel to defend key assets, military personnel, and citizens against Scud missiles launched by Iraqi forces.

Each battalion usually comprised of six batteries, with each battery containing a number of components including a single ground based radar unit used for surveillance target detection and tracking, an Engagement Control Station to control missile interceptors, eight missile launchers, as well as various communications and relay components.⁴

The Patriot’s weapon control computer performs crucial system functions for tracking and intercepting targets, as well as other control tasks. The system tracked and intercepted missiles in a number of stages:

1. The system was instructed to search for airborne objects with Scud missile characteristics (based on information such as velocity, latitude, longitude, azimuth, and altitude) on its radar.
2. A range gate, an electronic device in the radar, calculates an area in the air space for where the system should look next for the incoming missile. The missile is tracked by the system as it approaches.
3. The Patriot would launch one of it’s own missiles once the incoming missile was in range.

http://sydney.edu.au/engineering/it/~alum/patriot_bug.html

2.)What ethical decisions do you think the U.S Military made in choosing to deploy the Patriot missile to Israel and Saudi Arabia and in reporting the effectiveness of the Patriot system?

Shortly after Operation Desert Shield began, Patriot battalions were deployed to Saudi Arabia and then to Israel. These battalions were generally placed in permanent positions to defend key assets, military personnel, and citizens against Iraqi Scud missiles.
Because this was the first time the Patriot had been used to defend against Scud missiles, which fly at approximately MACH 5 (3750 mph), the Army had much to learn about tracking and intercepting them. To obtain Scud data, the Army relied on operational experience conveyed by Patriot users as well as other intelligence sources. With the launch of each Scud, the Army became more and more knowledgeable about the Scud's flight characteristics. Recorded data is another more useful tool that could have provided detailed data on the Patriot's actual performance. However, obtaining recorded performance data from Patriot units was hindered for two reasons.
First, the Patriot was not equipped with an embedded (internal) data recorder to retain system performance information. Second, although portable, external data recorders were available, U.S. commanders decided not to use them because they believed the recorders could cause an unanticipated system shutdown. However, Israeli commanders used data recorders on the Patriot systems they controlled and provided this data to the U.S. Army.

http://www.fas.org/spp/starwars/gao/im92026.htm

3.)What key lessons from this example of safety-critical software development could be applied to the development of business information system software?


Software development tools have direct and growing impact on the effective and efficient development of complex, safety-critical, real-time avionics systems and consequently on the safety of the flying public.  The developed avionics system software must be shown to comply with airworthiness requirements, which include functional, quality of service, and safety requirements.  The development processes performed by modern software development tools can be extremely complex and provide opportunities to automate the collection and documentation of evidence that the system requirements are met and that the development processes do not compromise the developed software requirements. 

http://www.tc.faa.gov/its/worldpac/techrpt/ar0636.pdf