Defense against UAV's

Jack Linthicum wrote:
[snip]


I think that a spread spectrum burst type transmission can be
intercepted and given a rough bearing. The money to do this is
miniscule in comparison with making Trident missiles into hand
grenades.

The command post does not move between transmissions. Spread
spectrum/frequency hopping systems return to previous frequencies every
few seconds. Just use several bursts to home in on the transmitter.

Andrew Swallow

Andrew Swallow wrote:
Jack Linthicum wrote:
[snip]


I think that a spread spectrum burst type transmission can be
intercepted and given a rough bearing. The money to do this is
miniscule in comparison with making Trident missiles into hand
grenades.

The command post does not move between transmissions. Spread
spectrum/frequency hopping systems return to previous frequencies every
few seconds. Just use several bursts to home in on the transmitter.
?? You transmit only when you want to issue new command to the swarm,
not to control every little thing. You can have minutes without
transmission, then 10ms transmission, followed by another long silence.

And you can also have plenty of cheap decoy trasmitters, just to make
it easier to intercept ... something. ;-)



Andrew Swallow

wrote:
Andrew Swallow wrote:
Jack Linthicum wrote:
[snip]

I think that a spread spectrum burst type transmission can be
intercepted and given a rough bearing. The money to do this is
miniscule in comparison with making Trident missiles into hand
grenades.
The command post does not move between transmissions. Spread
spectrum/frequency hopping systems return to previous frequencies every
few seconds. Just use several bursts to home in on the transmitter.
?? You transmit only when you want to issue new command to the swarm,
not to control every little thing. You can have minutes without
transmission, then 10ms transmission, followed by another long silence.


A machine can get a fairly accurate bearing in 10ms. Machines can be
made to be very patient so the several minutes is only a minor problem.
Several minutes allows wide angle receivers to be replaced by narrow
angle receivers sufficiently accurate to allow the targeting of weapons.

And you can also have plenty of cheap decoy trasmitters, just to make
it easier to intercept ... something. ;-)

Try brute force and ignorance - destroy the lot.

Andrew Swallow

In article ,
says...
Jack Linthicum wrote:
[snip]


I think that a spread spectrum burst type transmission can be
intercepted and given a rough bearing. The money to do this is
miniscule in comparison with making Trident missiles into hand
grenades.

The command post does not move between transmissions. Spread
spectrum/frequency hopping systems return to previous frequencies every
few seconds. Just use several bursts to home in on the transmitter.


Why are you assuming that the command post does not move? I see no
reason that a mobile command post and multiple mobile transmitters
could not be used.

Spread spectrum and frequency hopping systems do use a finite number
of frequencies---but the sequence of freqencies used may not repeat for
many hours. That leaves you with a broadband collection problem
and having to sort out multiple emitters on the same bandwidth with
different hopping schedules. I suspect that is a problem handled
offline and after-the-fact, and not in real time. However, the
technology has probably advanced a bit in the 30 years I've been
out of the sigint world. ;-)


Mark Borgerson

Mark Borgerson wrote:
In article ,
says...
Jack Linthicum wrote:
[snip]

I think that a spread spectrum burst type transmission can be
intercepted and given a rough bearing. The money to do this is
miniscule in comparison with making Trident missiles into hand
grenades.
The command post does not move between transmissions. Spread
spectrum/frequency hopping systems return to previous frequencies every
few seconds. Just use several bursts to home in on the transmitter.


Why are you assuming that the command post does not move? I see no
reason that a mobile command post and multiple mobile transmitters
could not be used.


This comes down to the definition of mobile. If the command post stays
in the same place for half an hour it is static. A constantly moving
command post would need a vehicle the size of a bus to hold the
operators and long range transmitters, possible but hard to camouflage.

Spread spectrum and frequency hopping systems do use a finite number
of frequencies---but the sequence of freqencies used may not repeat for
many hours. That leaves you with a broadband collection problem
and having to sort out multiple emitters on the same bandwidth with
different hopping schedules. I suspect that is a problem handled
offline and after-the-fact, and not in real time. However, the
technology has probably advanced a bit in the 30 years I've been
out of the sigint world. ;-)

If we are trying to destroy the command post we do not need to receive
the entire message we can simply wait until that frequency is reused by
that transmitter. If the equipment is hopping over 100 frequencies it
should be back within the next 200 transmissions.

The computers will need programming to treat transmissions from two
widely separated locations as two targets. Home in on them one at a time.

Andrew Swallow

"Keith W" wrote in message
...

wrote in message
oups.com...
[ SNIP ]
A UAV with realtime video image recognition and IR sensors is unlikely
to be especially cheap
Realtime video image recognition needs a source of video (probably a
wide-angle search camera + narrow angle scope with some decent
magnification for examining the suspicios contacts),

Problem 1 ) You have to process them to decide if they are suspicious

a decent CPU to do
the number crunching and a software to do the analysis. The first two
items are not particularly expensive. The software might take real
pains to develop, but afterwards the copies are free.

Understatement of the year
[ SNIP ]

If he can show the image processing and recognition problem to be easy, his
soon-to-be net worth will be more than that of Bill Gates. In fact, he'll
hire Billy just to supervise the programming staff to write the queuing
software for his executive bathroom.

Despite humongous amounts of research being done over many decades, general
computer vision remains an intractable problem. To illustrate, it may be
impossible for a vertical photograph (satellite) to differentiate between a
parking lot surrounded by a board fence and with a few cars parked on it,
and a large building with a flat roof and large roof vents, both with roads
nearby and under conditions of shadowing.

Now, in this case we'd certainly have a rules base codifying the knowledge.
But even restricting the problem to that of finding ships in the open ocean,
it's still not that simple. At a typical distance and altitude, a lot of
those ship lines are actually curves, so your algorithms need to recognize
smooth curves as part of a ship definition. Hmmmm, what else at sea is often
a fairly smooth curve?

I have a photo (8 1/2 by 11") of most of 4th MEB at sea, either 1990 or
1991. Fourteen vessels (LSTs, LPDs, LSDs, LPHs, one LHA, and a hospital
ship - no UNREP ships) are depicted. Going off the length of the LHA (shown
at a significant oblique), my estimate (very rough) is that the formation is
5-6 km across and perhaps 3 km deep. Even compressed like this - it's a
formation in time of hostilities that surely makes captains nervous - it's
still a collection with lots and lots of empty space. The colour contrast
and the wakes, the very calm conditions and excellent vizibility (light
haze) will at least allow a decent software to identify the ships as ships.
Leaving aside the hospital ship, I don't see that classifying most of the
vessels in the photograph would be anything other than a [very] difficult
recognition problem. A human can do it quickly, especially if cued with the
knowledge that everything is a USN gator, but it would be a pretty expensive
program that reliably typed each target.

One wonders too if the supposedly small and cheap UAV with the purportedly
inexpensive but sophisticated image recognition system is also fixing the
precise 3-D attitude of the airframe and hence the camera in order to allow
for estimating sizes of the objects in the picture, and _their_ attitude.
Forget relying on the horizon - in my picture you can barely make it out
because of haze. And it would have to be really precise data in order to get
good dimensional info.

What if you can't even see the wake, for one of several reasons? I'll give
the program three stars if it even correctly figures out what end of the
ship is which.

Now let's suppose that I am somewhat harsh in my analysis. Let's say that a
relatively coarse resolution picture and a basic analysis alerts the
software to "blobs of interest", and then the vehicle + camera is commanded
to do what it needs to do to get high-res images, and a better routine
analyzes these. Given some near optimal pictures - nearly side-on to the
vessel - you'd have something to work with. But in order to gauge size,
you'd need to be at some moderate altitude to have good geometry, under
which conditions superstructure begins to blend into the rest of the mass,
not be outlined against sky. In any case, with a large, detailed image of
the target, you now encounter other recognition problems e.g what details do
I ignore?

It is not a simple problem.

AHS

wrote:

rb wrote:

Highly unlikely that it went undetected for 25 mins.
More likely it's Iranian sabre rattling again.


Regardless of the accuracy of this particular account, it is true that
UAVs pose a new problem for navies and armies, especially in the
smaller versions. Defensive systems are generally designed to detect
and destroy much bigger and more obvious targets, and even if they
manage to spot a small UAV, what would be used to shoot it down?

This is the subject of much debate at the moment. Ordinary homing
missiles may not be able to lock-on to a stealthy little UAV (and even
if they could, there's not much logic in using a very expensive missile
to shoot down a very cheap plane). A radar-directed gun system like
Phalanx might also not lock-on to such a target. The best bet at the
moment IMO would be a 35mm gun firing the Oerlikon AHEAD 'shrapnel'
type airburst ammo, using electro-optical guidance.

Block 1B CIWS has an infrared and optical tracker that would do nicely
against any UAV within it's range...the question is finding the UAV in
the first place. An Infrared search system with the ability to designate
to a B1B Phalanx would work quite well I think...

....Ken

wrote:

:Almost all the arguments one sees here are based on the fact that UAVs
:are dumb and if you can take the comms out, you are fine. I am not
:sure that will hold for long, especially if the UAVs are used against
:ships on open sea, in fair weather, in 'kill every warship you see'
:mode - which all makes the autonomous decision making of the UAV so
:much easier. Design for minimal communication and bandwidth needs
just for higher level commands/coordination) - much tougher to detect
:and jam.

I just had this conversation at work today. Your application requires
ATR on the part of the UAV. ATR is a hard problem (to the point of
being largely impossible in the general case).

:It is easy to imagine a swarm of UAVs used as very sheap relatively
:slow (200km/h) flying cruise missiles with small warheads, designed to
:attack radars and similar on-ship targets that can be seriously damaged
:with a small warhead

Ok, now you're talking about radar homers, which are easier (in other
words, they're possible). But they're either easily decoyed or they
start getting expensive.

spray a shotgun of darts with wavy aluminium
:tails into that phased array and see what it can do afterwards).

Pretty much what it could before, only slightly degraded.

--
"Millions for defense, but not one cent for tribute."
-- Charles Pinckney

In article ,
says...
wrote:
Andrew Swallow wrote:
Jack Linthicum wrote:
[snip]

I think that a spread spectrum burst type transmission can be
intercepted and given a rough bearing. The money to do this is
miniscule in comparison with making Trident missiles into hand
grenades.
The command post does not move between transmissions. Spread
spectrum/frequency hopping systems return to previous frequencies every
few seconds. Just use several bursts to home in on the transmitter.
?? You transmit only when you want to issue new command to the swarm,
not to control every little thing. You can have minutes without
transmission, then 10ms transmission, followed by another long silence.


A machine can get a fairly accurate bearing in 10ms. Machines can be
made to be very patient so the several minutes is only a minor problem.
Several minutes allows wide angle receivers to be replaced by narrow
angle receivers sufficiently accurate to allow the targeting of weapons.


Narrow angle receivers require larger antennas or arrays of antennas.
Granted, that is easier at 900 Mhz than at 9Mhz.

Several minutes between hits on a narrowband frequency is different than
several hours---particularly if your platform is moving. Then you
get into problems with how accurately you know the position and
heading of the platform. Much more difficult than DF from a fixed
land base.
And you can also have plenty of cheap decoy trasmitters, just to make
it easier to intercept ... something. ;-)

Try brute force and ignorance - destroy the lot.
How many missiles will that take?


Mark Borgerson

"Keith W" wrote:

:"ray o'hara" wrote in message
...
:
: laser guided weapons gave a tendency to attack the sun. you only see the
: good ones on tv, not all the misses.
:
:Utter ********, the laser sensors look for reflected light at
:specific frequencies

Ray is, as usual, being an idiot. Not only reflected light at
specific frequencies, but with a specific code.

: rocks eated by the sun. reflections off of pools of water or streams can
: also distract them.
:
:You seem not to understand the difference between IR and laser sensors

He's also the better part of a century behind when it comes to IR,
since IIR weapons (what he seems to be referring to) have very little
problem with practically everything he mentions.

He apparently thinks laser weapons home on heat. Hell, even IR strike
weapons don't do that!

--
"Ignorance is preferable to error, and he is less remote from the
truth who believes nothing than he who believes what is wrong."
-- Thomas Jefferson