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From: Rune Allnor on 13 Sep 2009 15:10 On 13 Sep, 20:52, Richard Owlett <rowl...(a)pcnetinc.com> wrote: > steveu wrote: > > >> Dirk Bell wrote: > > >>> On Sep 10, 8:08 pm, "steveu" <ste...(a)coppice.org> wrote: > > >>>> The kinds of things people do in military systems tends to be a lot > >>>> different from most non-military work. I guess that in the 70s, 90% of > > all > >>>> copies of O&S and Rabiner and Gold sold to people in military work, who > > had > >>>> not studied anything about DSP at college - because very few colleges > > had > >>>> begun DSP courses - and who needed to get a clue what they were doing. > > Its > >>>> a while since I looked at either book, but I remember once reflecting > > on > >>>> how the contents seemed to reflect that heritage. > > >>> Having read both books in the early 80's, I didn't get that > >>> impression. > >> I don't have Rabiner and Gold at hand right now, but IIRC it is biased > >> towards the radar signal processing. When they give an example of a > >> technique, they often mention some kind of military application. And > >> yes, R&G used to be a handbook of people who actually worked on radars. > > > Ah, those were the days. With Rabiner and Gold in one hand, and Skolnick > > in the other, we fought the evils of communism. :-) > > > Steve > > IIRC NORAD radar system once reported massive incoming missile > attack from "nowhere" (or more definitively 'no place') > > OOOPS, moon rise > > Later blamed on "computer error" related to anomalous return time > of echoes. > Might it have more with moving from a 'continuous' to 'discrete' > domain? Don't know about NORAD, but a similar story circulated about Soviet early warning systems: http://www.wired.com/science/discoveries/news/2007/09/dayintech_0926 This particular story seems to have been caused by people looking for a particular signature associated wuth ICBMs without realizing that there might be other non-related sources of similar signatures. This is, of course, the perpetual Achilles heel of 'smart' systems: They only work as long as the underlying assumptions actually hold. Don't be surprised if at least some of the NORAD stories were caused by similar reasons. Rune
From: Jerry Avins on 13 Sep 2009 15:38 Rune Allnor wrote: > On 13 Sep, 20:52, Richard Owlett <rowl...(a)pcnetinc.com> wrote: >> steveu wrote: >> >>>> Dirk Bell wrote: >>>>> On Sep 10, 8:08 pm, "steveu" <ste...(a)coppice.org> wrote: >>>>>> The kinds of things people do in military systems tends to be a lot >>>>>> different from most non-military work. I guess that in the 70s, 90% of >>> all >>>>>> copies of O&S and Rabiner and Gold sold to people in military work, who >>> had >>>>>> not studied anything about DSP at college - because very few colleges >>> had >>>>>> begun DSP courses - and who needed to get a clue what they were doing. >>> Its >>>>>> a while since I looked at either book, but I remember once reflecting >>> on >>>>>> how the contents seemed to reflect that heritage. >>>>> Having read both books in the early 80's, I didn't get that >>>>> impression. >>>> I don't have Rabiner and Gold at hand right now, but IIRC it is biased >>>> towards the radar signal processing. When they give an example of a >>>> technique, they often mention some kind of military application. And >>>> yes, R&G used to be a handbook of people who actually worked on radars. >>> Ah, those were the days. With Rabiner and Gold in one hand, and Skolnick >>> in the other, we fought the evils of communism. :-) >>> Steve >> IIRC NORAD radar system once reported massive incoming missile >> attack from "nowhere" (or more definitively 'no place') >> >> OOOPS, moon rise >> >> Later blamed on "computer error" related to anomalous return time >> of echoes. >> Might it have more with moving from a 'continuous' to 'discrete' >> domain? > > Don't know about NORAD, but a similar story circulated about > Soviet early warning systems: > > http://www.wired.com/science/discoveries/news/2007/09/dayintech_0926 > > This particular story seems to have been caused by people > looking for a particular signature associated wuth ICBMs > without realizing that there might be other non-related > sources of similar signatures. > > This is, of course, the perpetual Achilles heel of 'smart' > systems: They only work as long as the underlying assumptions > actually hold. > > Don't be surprised if at least some of the NORAD stories > were caused by similar reasons. The NORAD incident was a good strong return off the moon, perfectly normal. The range counter didn't have enough bits to indicate the true distance. Wraparound error put the distance somewhere over the North Pole. Our "retaliatory" missiles were within a minute of being launched. Jerry -- Engineering is the art of making what you want from things you can get. �����������������������������������������������������������������������
From: Rune Allnor on 13 Sep 2009 16:58 On 13 Sep, 21:38, Jerry Avins <j...(a)ieee.org> wrote: > >> IIRC NORAD radar system once reported massive incoming missile > >> attack from "nowhere" (or more definitively 'no place') > > >> OOOPS, moon rise > > >> Later blamed on "computer error" related to anomalous return time > >> of echoes. > >> Might it have more with moving from a 'continuous' to 'discrete' > >> domain? > > > Don't know about NORAD, but a similar story circulated about > > Soviet early warning systems: > > >http://www.wired.com/science/discoveries/news/2007/09/dayintech_0926 > > > This particular story seems to have been caused by people > > looking for a particular signature associated wuth ICBMs > > without realizing that there might be other non-related > > sources of similar signatures. > > > This is, of course, the perpetual Achilles heel of 'smart' > > systems: They only work as long as the underlying assumptions > > actually hold. > > > Don't be surprised if at least some of the NORAD stories > > were caused by similar reasons. > > The NORAD incident was a good strong return off the moon, perfectly > normal. The range counter didn't have enough bits to indicate the true > distance. Wraparound error put the distance somewhere over the North > Pole. Our "retaliatory" missiles were within a minute of being launched. ....which invalidated the implicit/hidden/forgotten assumption that 'moon returns are irrelevant.' It was not a 'computer error.' It was a design flaw in the system. Rune
From: Jerry Avins on 13 Sep 2009 19:11 Rune Allnor wrote: > On 13 Sep, 21:38, Jerry Avins <j...(a)ieee.org> wrote: > >>>> IIRC NORAD radar system once reported massive incoming missile >>>> attack from "nowhere" (or more definitively 'no place') >>>> OOOPS, moon rise >>>> Later blamed on "computer error" related to anomalous return time >>>> of echoes. >>>> Might it have more with moving from a 'continuous' to 'discrete' >>>> domain? >>> Don't know about NORAD, but a similar story circulated about >>> Soviet early warning systems: >>> http://www.wired.com/science/discoveries/news/2007/09/dayintech_0926 >>> This particular story seems to have been caused by people >>> looking for a particular signature associated wuth ICBMs >>> without realizing that there might be other non-related >>> sources of similar signatures. >>> This is, of course, the perpetual Achilles heel of 'smart' >>> systems: They only work as long as the underlying assumptions >>> actually hold. >>> Don't be surprised if at least some of the NORAD stories >>> were caused by similar reasons. >> The NORAD incident was a good strong return off the moon, perfectly >> normal. The range counter didn't have enough bits to indicate the true >> distance. Wraparound error put the distance somewhere over the North >> Pole. Our "retaliatory" missiles were within a minute of being launched. > > ...which invalidated the implicit/hidden/forgotten > assumption that 'moon returns are irrelevant.' It was not > a 'computer error.' It was a design flaw in the system. Certainly a design flaw, a hardware design flaw that was rectified by adding bits to the range counter. There was no general-purpose computer involved. We were saved from launching WWIII by a level-headed officer who noticed that altitude was rising unbelievably fast and range was behaving a bit erratically. He ordered a stand-down. Do we still have people in the system? Jerry -- Engineering is the art of making what you want from things you can get. �����������������������������������������������������������������������
From: steveu on 13 Sep 2009 19:45
>...which invalidated the implicit/hidden/forgotten >assumption that 'moon returns are irrelevant.' It was not >a 'computer error.' It was a design flaw in the system. > >Rune Almost everything described as a "computer error" is a design problem in the system. Steve |