Smoke, mirrors and the GBU - 12

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.

"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.

"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) wrote in message . com...
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

"Xenia Dragon" wrote in message
om...
(Xenia Dragon) wrote in message
. com...
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.

"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

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.)

"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 ...

"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.

"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