Re: Patriot Missile Software Problem

Re: Patriot Missile Software Problem

[Harry Erwin]

Reminds me of the Thanksgiving rollover problem on Site Defense.
   Cheers,
-- 
Harry Erwin
Internet: erwin@trwacs.fp.trw.com

Re: Patriot Missile Software Problem

[Bill Hefley]

In article <9204172209.AA05774@ajpo.sei.cmu.edu> SAHARBAUGH@ROO.FIT.EDU writes:
>You may find this report interesting and thought provoking:
>
>GAO/IMTEC-92-26 Patriot Missile Software Problems, 
>16 pages, available from 
>US General Accounting Office
>PO Box 6015
>Gaithersburg, MD 20877
>or call (202) 275-6241
>1st copy free, additional $2 each
>
I don't want to quibble with Sam, as he not only points out the software
deficiency, but also questions how else this problem might have been
encountered and whether it could have been influenced by language and hardware
choices. 

Careful readers, trying to understand WHY this terrible incident happened,
need to look beyond just the technological problems, though.   Page 9 of this
GAO has a section entitled "Patriot Project Office Response to Anomaly."  This
sectionpoints out that Army officials assumed Patriot users were not running
their systems for more than 8 hours at a time.

Direct quote:
"On February 21, 1991, the Patriot Project Office sent a message to Patriot
users stating that very long run times could cause a shift in the range gate,
resulting in the target being offset.  The message also said a software change
was being sent that would improve the system's targeting. However, the message
did not specify what constitutes very long run times.  According to Army
officials, they presumed that the users would not continuously run the
[Patriot] batteries for such extended periods of time that the Patriot would
fail to track targets. Therefore, they did not think that more detailed
guidance was required."

These problems are independent of any implementation language or hardware --
they have to do with understanding the operational environments of our
systems, defining clearly and precisely what we mean (requirements), and
communicating these to those who need to know (requirements specs). From this
report, the Army program office knew of the difficulty of "very long run
times," but it isn't clear that they understood the implication in the
operational setting, nor forcefully communicated guidance to alleviate the
problem.