Smoke, mirrors and the GBU - 12

[Xenia Dragon]

Yesterday I read two articles on laser assisted
bombing which were quite satisfying but still
managed to leave me wondering about the technology
and the possibility of employing countermeasures
during weapon delivery.
Without giving away any "state secrets" perhaps
someone on rec.aviation,military could dispell
my idle thoughts on future possibilities?

In description of F15 strikes in Afghanistan
one author described instances where cloud cover
prevented the AC from lasing ground targets.
Numerical recognition codes required by the
F15 mounted laser and its bomb were relayed
by pilot voice (encrypted?) to well trained
FACs on the ground who punched the codes into their
man portable units. The GBU-12s were dropped
and completed flight under control of the FACs
using battery powered lasers aimed at their
targets, usually armour.

Question - how many times per second is the
recognition code transmitted on the beam or
is it continuous? When the laser is reflected
off of the target how widely dispersed does
the beam become and what happens to information
encoded in the laser beam? (If I am not
understanding the process, please explain.)
Assuming that countermeasures
are designed for a particularly costly and
sensitive military asset, what would be the
approximate configuration of kit designed to
acquire the beam, decode the signal, and turn
on countermeasures to make the bomb miss?
....because of course you cannot stop F15s from
flying or their bombs from being dropped.

Thankyou.

[Tarver Engineering]

"Xenia Dragon" > wrote in message
om...

<snip>
> Question - how many times per second is the
> recognition code transmitted on the beam or
> is it continuous? When the laser is reflected
> off of the target how widely dispersed does
> the beam become and what happens to information
> encoded in the laser beam? (If I am not
> understanding the process, please explain.)

The laser light is a carrier, just like a radio signal. The easiest way to
modulate information onto a laser is acoustically.

> Assuming that countermeasures
> are designed for a particularly costly and
> sensitive military asset, what would be the
> approximate configuration of kit designed to
> acquire the beam, decode the signal, and turn
> on countermeasures to make the bomb miss?

A laser is very directional and intercepting the signal would require you to
be in line of sight between the laser and the designated target. This may
not be a survivable place to be, as you are now lased.

> ...because of course you cannot stop F15s from
> flying or their bombs from being dropped.

Some have tried.

[Simon Robbins]

"Tarver Engineering" > wrote in message
...
>
> The laser light is a carrier, just like a radio signal. The easiest way
to
> modulate information onto a laser is acoustically.

Please explain what you mean, surely acoustics constitutes information and
not a modulation method? I'd have thought the easiest way to encode
information onto a laser carrier would be pulse-code modulation.

Si

[Xenia Dragon]

(Xenia Dragon) wrote in message >...
> Yesterday I read two articles on laser assisted
> bombing which were quite satisfying but still
> managed to leave me wondering about the technology
> and the possibility of employing countermeasures
> during weapon delivery.
> Without giving away any "state secrets" perhaps
> someone on rec.aviation,military could dispell
> my idle thoughts on future possibilities?
>

A followup note - Steve Davies page on the Strike Eagles
has a text only "Links to Strike" page which contains the
most detail I can find concerning F15 coordination with
Special Forces and FACs in Afghanistan. There is description
of the electronics including the security of communication
and maintaining integrity of the laser guidance, but still
I cannot find answers that I seek.
Mark Bowden's article THE KABUL-KI DANCE in 2002 on
the 391st FS is a must read, by the way.

Cheers. Xenia

[Tarver Engineering]

"Xenia Dragon" > wrote in message
om...
> (Xenia Dragon) wrote in message
>...
> > Yesterday I read two articles on laser assisted
> > bombing which were quite satisfying but still
> > managed to leave me wondering about the technology
> > and the possibility of employing countermeasures
> > during weapon delivery.
> > Without giving away any "state secrets" perhaps
> > someone on rec.aviation,military could dispell
> > my idle thoughts on future possibilities?
> >
>
> A followup note - Steve Davies page on the Strike Eagles
> has a text only "Links to Strike" page which contains the
> most detail I can find concerning F15 coordination with
> Special Forces and FACs in Afghanistan. There is description
> of the electronics including the security of communication
> and maintaining integrity of the laser guidance, but still
> I cannot find answers that I seek.
> Mark Bowden's article THE KABUL-KI DANCE in 2002 on
> the 391st FS is a must read, by the way.

You probably will find what you seek is classified information.

[Simon Robbins]

"Tarver Engineering" > wrote in message
...
> Acoustic coupling is a way information is amplitude modulated onto a laser
> carrier.

I can see how that would work, but it would be very susceptible to
atmospheric pollution and signal degradation. Anything that would weaken the
strength of your laser light at the destination would play havoc with
amplitude modulation.

> Morris code?

Not familiar with that.

Si

[Andrew Chaplin]

Tarver Engineering wrote:

> Morris code?

Morse code.

Morris code:

Meow = feed me
Meow, meow = feed me
Brrrup = get that plate of food down here, pronto!
Meow, meow, meow = get over here and open the door
Mrauw, mrauw = I'm going to puke on the Persian rug.
--
Andrew Chaplin
SIT MIHI GLADIUS SICUT SANCTO MARTINO
(If you're going to e-mail me, you'll have to get "yourfinger." out.)

[Tarver Engineering]

"Simon Robbins" > wrote in message
...
>
> "Tarver Engineering" > wrote in message
> ...
> > Acoustic coupling is a way information is amplitude modulated onto a
laser
> > carrier.
>
> I can see how that would work, but it would be very susceptible to
> atmospheric pollution and signal degradation.

How? What you wrote is non-sensical.

> Anything that would weaken the
> strength of your laser light at the destination would play havoc with
> amplitude modulation.

No, but pcm is going to blink the laser.

> > Morris code?
>
> Not familiar with that.

Think about it. blink blink blink ...

[Tarver Engineering]

"Simon Robbins" > wrote in message
...
>
> "Tarver Engineering" > wrote in message
> ...
> > > I can see how that would work, but it would be very susceptible to
> > > atmospheric pollution and signal degradation.
> >
> > How? What you wrote is non-sensical.
>
> I don't think so. Amplitude modulating information onto a light carrier
> would mean that any atmospheric interference, such as haze, smoke, etc.
> would have the effect of corrupting the modulation levels compared to the
> signal carrier mean signal to noise, much like ambient RF interference has
a
> huge effect on amplitude modulated radio.

The smoke and atmospheric interference you describe make the laser deginator
non-operable.

> Blinking the laser, as with PCM wouldn't interfere as much since it's an
all
> or nothing signal. So, providing the laser source wasn't completely
> obscurred, the information would still be recoverable. The bit-rate would
> presumably be fast enough that a seeker wouldn't loose lock during the
zero
> states.

You miss the reason for the laser being there in the first place.

[Simon Robbins]

"Tarver Engineering" > wrote in message
...
>
> The smoke and atmospheric interference you describe make the laser
deginator
> non-operable.

Only in extreme cases. Humidity, mild dust and other airborne particulates
will degrade the laser's performance but not necessarily block it
completely.

> You miss the reason for the laser being there in the first place.

No, a high bit rate of modulated binary data is not going to force the
seeker to loose lock if the seeker algorithm is written to handle it. Or
perhaps the technology is a lot less mature than I imagined it to be.

Si

[[email protected]]

(B2431) wrote:

>>
>>
>>"Tarver Engineering" > wrote in message
...
>>> Acoustic coupling is a way information is amplitude modulated onto a laser
>>> carrier.
><snip>
>>
>>> Morris code?
>>
>>Not familiar with that.
>>
>>Si
>>
>Translation from Traver to English: morris code = morse code.
>
>Dan, U. S. Air Force, retired

And...oddly enough...translating Tarver to English yields exactly
the same results!!!... :) (he's a very talented lout indeed!)
--

-Gord.

[Xenia Dragon]

"Simon Robbins" > wrote in message >...
> "Tarver Engineering" > wrote in message
> ...
> >
> > The smoke and atmospheric interference you describe make the laser
> deginator
> > non-operable.
>
> Only in extreme cases. Humidity, mild dust and other airborne particulates
> will degrade the laser's performance but not necessarily block it
> completely.
>
> > You miss the reason for the laser being there in the first place.
>
> No, a high bit rate of modulated binary data is not going to force the
> seeker to loose lock if the seeker algorithm is written to handle it. Or
> perhaps the technology is a lot less mature than I imagined it to be.
>
> Si


THANKS to all those who took the time to help with my query.
It was good of you. I have since done some persistent
Googling and find that in addition to the country
mentioned in the thread there are other nations, including
China, which have products to defeat laser targeting of their ground
positions. The US military in turn is aware of all countermeasures
to its laser guided bombs and has contracted research on
improvements which will continue to make it difficult for those
countries with only a basic defensive capabiility to oppose
US policy initiatives. As a lay person I only need basic info
on the subject.

Cheers Xenia

[GregD]

(B2431) wrote:

> Translation from Traver to English: morris code = morse code.

No, they are different. Tarver *invented* Morris Code, back when
he single-handedly (hehe, there's an image for you) designed the
Boeing 777, remember? Tarver's Morris Code consisted of a 3x3
matrix of 'x' and 'o' characters, not the serial stream dots and
dashes of the more common Morse Code. :)

GregD

[IBM]

(GregD) wrote in
om:

> (B2431) wrote:
>
>> Translation from Traver to English: morris code = morse code.
>
> No, they are different. Tarver *invented* Morris Code, back when
> he single-handedly (hehe, there's an image for you) designed the
> Boeing 777, remember? Tarver's Morris Code consisted of a 3x3
> matrix of 'x' and 'o' characters, not the serial stream dots and
> dashes of the more common Morse Code. :)

Morris Code?
Isn't that where you send messages by means of hanky, drum and
tin whistle? Bit of a bitch to work since it required a 10
man detachment in its most elaborate form and was not to be
attempted under fire.
I think they retired the Morris Code MOS after it was demonstrated
to be the leading cause of friendly fire incidents.

IBM

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[Tarver Engineering]

"John R Weiss" > wrote in message
et...
> "GregD" > wrote...
>
> > No, they are different. Tarver *invented* Morris Code, back when
> > he single-handedly (hehe, there's an image for you) designed the
> > Boeing 777, remember? Tarver's Morris Code consisted of a 3x3
> > matrix of 'x' and 'o' characters, not the serial stream dots and
> > dashes of the more common Morse Code. :)
>
> Further, the 'x' and 'o' characters on one or more matrices could then be
> translated into sounds and spaces:

Acousticly coupled DTMF should work just fine.