Re: [SystemSafety] The Patriot Missile Failure (was Re: systemsafety Digest, Vol 34, Issue 5)

From: Matthew Squair < >
Date: Wed, 6 May 2015 09:11:07 +1000


Hi Martyn,

The time, along with position and velocity, is used in the calculation of a parameter called the range gate which is used in track while scan radar systems to tell the radar where to expect (correlate) a radar return for a tracked object. Clock drift can cause the gate to drift away from the actual radar return's location, once the difference gets past a certain threshold the radar return and track will decorrelate and the radar will loose (or drop) the track.

The actual details of how this occurred on the day are a little more complex, if you're interested see the case study at the link for more detail http://wp.me/ax0Kp-2tK.

On Tue, May 5, 2015 at 6:56 PM, Martyn Thomas < martyn_at_xxxxxx

> Why did they need to keep the time, over a period of 100 hours, in order
> to determine how far away an incoming missile is? The two things appear to
> me to be unrelated.
>
> Martyn
>
> On 04/05/2015 21:57, Steve Tockey wrote:
>
>
> Can static analysis catch this kind of defect:
>
> https://www.ima.umn.edu/~arnold/disasters/patriot.html
>
>
>
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-- 
*Matthew Squair*
MIEAust CPEng

Mob: +61 488770655
Email: MattSquair_at_xxxxxx
Website: www.criticaluncertainties.com <http://criticaluncertainties.com/>



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