The computer used to control the Patriot missile is based on a 1970s design and uses 24-bit arithmetic. The Patriot system tracks its target by measuring the time it takes for radar pulses to bounce back from them. Time is recorded by the system clock in tenths of a second, but is stored as an integer. To enable tracking calculations the time is converted to a 24-bit floating point number. Rounding errors in the time conversions cause shifts in the system's ``range gate", which is used to track the target.

1. The Dhahram Patriot
Missile Failure

2. Introduction
•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.

3. When it was developed and the cost of
it...
● Full-scale development of the system began in 1976.
● And it was deployed in 1984.
● Patriot was used initially as an anti-aircraft system, but during 1988, it
was upgraded to provide limited capability against tactical ballistic
missiles.
● And Talking about the unit cost,it over 2 million dollars.

4. What is the purpose
● 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.

5. What Was The Failure
The cause was an inaccurate calculation of computer arithmetic errors.
A small timing error in the system’s clock accumulated to the point that
after 14 hours, the tracking system was no longer accurate.In the Dhahran
attack, the system had been operating for more than 100 hours.
The software truncated the 24-bit numbers when converting to binary
This truncation error grew the longer the system ran.

6. Cost of Failure
Because the system had been on so long, the resulting inaccuracy in the
time calculation caused the range gate to shift so much that the system
could not track the incoming Scud. Consequently, Alpha Battery did not
engage the Scud, which then struck an Army barracks and killed 28
American soldiers. Around 100 people were injured.

8. Any Questions
?

9. Thank you