Re: laser targeting

On Jan 10, 8:13�am, obviouslydelusional
<obviouslydelusio...@gmail.com> wrote:

On Jan 9, 10:20�pm, "m...@sushi.com" <m...@sushi.com> wrote:

This is the range where you would see laser spotting. I've camped out
there and the area is pretty busy with auto traffic, but I suspect all
the bombing and thus targeting is over the next ridge.

http://www.lazygranch.com/stonewall_mountain.htmhttp://www.lazygranch...


The following 135 page pdf document is everything the military wants
you to know about laser safety in the field. �Being from 1996, it's
probably a little dated, but it puts you in the ballpark. �Of
particular note is Appendix A, which lists "Nominal Ocular Hazard
Distances" for a variety of laser equipped targeting and weapons
systems. �It also gives the safe distances when using magnifying
optics (binos, scopes, etc). �They are rather....large. �It makes one
wonder about watching Red Flag ops with binos.

http://chppm-www.apgea.army.mil/laser/Publications/MIL828/828a.pdf


Yeah,  I came across that when I googled on the ranging. It shows how
they want to target the laser so that the angle isn't very steep,
which makes it less likely to reflect back at you.

I think the only place you might encounter laser targeting is on live
fire ranges. Certainly the range next to Stonewall since they have the
warning sign. I think the likelihood of being a laser target of
opportunity is low. The class 4 laser really packs a punch. No, they
will just radar lock on us.

When I photographed the yellow junker truck in the hills east of the
ET Highway, I couldn't open my car doors with the keyless remote. I'm
sure they were hitting me with some RF and desensing the remote
system.

I have thought a bit more about what it would take to detect being
targeted with LIDAR type pulses. I was thinking you would need enough
bandwidth to reproduce the pulse. But pondering a bit more on the
task, I thought of pulse detection schemes. Generally you try not to
use pulses in communications since they eat bandwidth for no good
reason. [Noise is propoertional to the square root of the bandwidth.]
That is, you send shaped pulses like raised cosine (technically root
raised cosine for matched filtering]. But if you had to send pulses,
the general demod is integrate and dump It is just like is sounds. You
integrate the flat pulse, which in turn becomes a ramp. When the ramp
is sufficiently high, you declare the pulse detected and start the
dump cycle, which means reset the integrator.

Now if you were being hit with LIDAR pulses, what you would do is set
the bandwidth of the receiver low enough that the time constant equals
the pulse width. That gives you the magic number (68% IIRC) of the
integrated pulse reaching the final value. So a band limited receiver
is like an integrate and dump. If they hit you with more than one
pulse, even better. Set the bandwidth lower and integrate a few
pulses. So it is possible with a modest optical receiver (say 20MHz
bandwidth), you could sense being detected by their targeting system.

What I haven't computed is amount of energy directed at the target,
which in turn determines the signal to noise ratio. But with the
reduced bandwidth, you can actually pulse the signal out of the noise
since the noise will be zero mean, i.e. it will integrate to zero,
while the pulses will be additive. The specs are there to make this
calculation. That is, the divergence of the beam is known, as well as
the power output.

Of course, now you have to wonder if Al Qaeda has a "holy crap I'm
being targeted" device. Who knows, maybe an off the shelf radar/lidar
detector would work, though the laser frequency would be off a bit.
The police lidar is 900 or 950nm, while the military is using
something a bit longer than a micron. So the optical filter and
perhaps sensor would need to be changed.

I don't believe I have any weapons school audio of laser targeting,
but the buzzword is "sparkle."