Posted on 01/09/2003 4:18:02 PM PST by MeekOneGOP
FOX News Breaking:
Iraq may have purchased GPS jammers from Russians
![[gpsjam-7]](http://www.qsl.net/n9zia/wireless/pics/gpsjam-7.jpg)
![[gpsjam-8]](http://www.qsl.net/n9zia/wireless/pics/gpsjam-8.jpg)
SUMMARY: (U) CONFEX - THE RUSSIAN FIRM AVIACONVERSIA MARKETED AND DISPLAYED ITS PORTABLE GPS AND GLONASS JAMMER AT THE MOSCOW AIR SHOW '97, 19-24 AUG 97, IN MOSCOW, RUSSIA. THE 4-WATT JAMMER JAMS CIVILIAN AND MILITARY FREQUENCIES OF GPS AND GLONASS UP TO A RANGE OF 200 KM. PROTOTYPE AT THE SHOW - LOOKING FOR BUYERS.
Tuesday, September 24, 2002 Posted: 11:29 PM EDT (0329 GMT)
Editor's Note: CNN Access is a regular feature on CNN.com providing interviews with newsmakers from around the world.
|
||
|
Story Tools
|
||
ATLANTA, Georgia (CNN) -- With a plan for a possible war against Iraq sitting on President Bush's desk, there is a disturbing report that "smart bombs" in the U.S. arsenal, which would likely be used in any strikes on Baghdad, may have an Achilles heel.
A cheap, easy-to-get device could interfere with the weapons' guidance systems, possibly disrupting surgical strikes and endangering civilians the bombs were designed to avoid, The Wall Street Journal reported Tuesday.
CNN anchor Kyra Phillips discussed the report with CNN military analyst, retired Air Force Maj. Gen. Don Shepperd who explained how such "smart" weapons work.
SHEPPERD: The JDAM is Joint Direct Attack Munition, and basically what it is, it's a satellite-guidance component that is put on the tail of a weapon. It moves the fins, it directs it to the set of coordinates that you program in.
Unfortunately, it has been called a satellite-guided weapon. It is not satellite guided. It is guided by an inertial navigation system (INS) that guides it to the coordinates. The Global Positioning System (GPS) mode of it basically updates and makes the INS more accurate. So, it is satellite-assisted, not satellite-guided.
PHILLIPS: OK, big difference. So then, let's talk about this article and ... these jammers -- you are able to purchase one on the Internet for 40 bucks. Is in the same type of jammer that the U.S. military would use?
SHEPPERD: Well, I will stay away from what the U.S. military would use, but it is the type of jammer that Saddam Hussein might use in Iraq.
Basically, it is very cheap to jam GPS signals. You can do it with these low-powered and cheap jammers. However, when we designed the weapon, we had this in mind. And what happens when the weapon basically gets information that it has lost the satellite signal, or it is being confused and jammed, it then reverts to its INS mode, its Inertial Navigation System.
It makes it less accurate, but let me give you kind of a range: Let's say it is a 5-meter, or 15-foot, bomb with the GPS signal. It would go, maybe, to a 15- or 20- meter, a 45-, 50-, 60-foot bomb without it. Therefore, it doesn't mean -- with a blast radius of, say, 150 feet -- that it is a useless bomb by any means. It is just less accurate than it would be with the GPS signal.
PHILLIPS: Well, in an area like Baghdad, it is not like Afghanistan with this vast desert area. It is very small, so accuracy is so crucial. So does this concern you at all?
SHEPPERD: It does concern us, and of course, when you degrade the accuracy of precision munitions, it is still a concern. When you go in downtown Baghdad, in populated areas, and you want to hit a military vehicle that is next to a hospital, you want it to be very, very accurate. You want a 5-meter bomb. And if it is jammed, and goes to 15- or 20-meter, it could affect the accuracy. So Saddam Hussein has to think that by jamming it, it could divert some of our weapons into his populated areas, if he cares.
PHILLIPS: Well, general, have GPS signals ever been jammed in battle? Do we know that?
SHEPPERD: Again, I need to stay away from that. It is possible to jam GPS signals in battle. Whether or not it has actually been done and the effect of it is not something that I care to discuss right now, but it is possible. It just makes them less accurate and not useless.
PHILLIPS: Can we talk about what we really know with regard to the extent of our GPS's vulnerability?
SHEPPERD: Well, the GPS is vulnerable in that you can jam satellite signals. There is a commercial and a military use, and the commercial side is used to locate the military signal, if you will. So the military is much harder to jam, and it is a different signal entirely, but we are vulnerable.
On the other hand, again, it doesn't mean the weapons are useless, it just means that, maybe, their accuracy is two or three times the 5 or 10 meters that you would like to have.
PHILLIPS: Are efforts underway to upgrade the satellites?
SHEPPERD: There are constant efforts to increase the reliability of the signal. All of those are highly classified. We won't be told what they are doing out there, but we are constantly looking at upgrading this accuracy and making sure the signals are reliable.
Which suggests to me that the Pentagon evaluated the threat and decided they could counter it.
GPS signals are difficult to jam. They are spread spectrum signals. The spreading "key" can be an encrypted one, but that's just to deny use of the GPS signal to ones enemies. My understanding is that they turned off the encryption some years ago. The problem is that you apparenly can't just turn if off for one area, but rather you must do so for the entire world. It only denies the "fine" or high accuracy capability, your GPS would continue to work, but the fix wouldn't be sufficiently accurate to use in precision guided weapons, unless you had the proper "key". It would make your GPS Map kind somewhat less usefull, and forget about landing an airplane or taxiing in the fog, or bringing a boat/ship into harbor and to the dock if you can't see the dock.
There are ways to counter the jamming too. A bit pricey for something you'd buy at WalMart, and maybe not practical for any hand held unit, but for vehicle, (or munition) mounted sets, an active antenna that can null out the jamming signal can be used. I'm sure there are other techniques, but if I knew them, I'd probably have to shoot whoever I told 'em to.
Joe Katzman discovered an article which made him afraid that our GPS-guided weapons could be defeated with a simple commercial jammer produced in Russia which can be bought for $39.95. I'm not too concerned.
A normal civilian GPS receiver uses an omnidirectional whip antenna, so that any signal from any direction is received equally. I would be very surprised if JDAMs do so. I think it's pretty obvious that any jamming would be coming from near the ground, and that the true GPS signal would be coming from the sky, and it isn't very difficult to design an antenna which selects signals from only one direction or set of directions, and physically rejects signals from all others. Since the bomb that a JDAM is attached to will always assume a standard orientation when it's falling (nose down) it would be quite easy to incorporate a directional antenna into the JDAM, and that alone would go a long way towards solving the problem.
CPO Sparkey works on this stuff and thus can't comment, except to say, "Come on Saddam, just stand still with all the dinky little Internet jammers you can buy just piled around you, please, oh please, oh please!”. It probably should be pointed out that a jammer is a prime target for HARM or equivalent weapons, and by its nature it cannot hide. If a high value target surrounded itself with jammers like this, it would be like painting a target on the site.
I don't on military hardware, but I've worked on related civilian technologies, so perhaps I can offer some speculation.
The original GPS system uses a form of direct-sequence spread spectrum (DSS) for its signals. The CDMA cell phones I used to work on use a much more sophisticated version of the same thing. What has to be understood is that DSS is designed to ignore substantial amounts of environmental noise. The signal in DSS is scrambled using what's known as "pseudo-noise", or PN, which is a carefully crafted sequence of bits known to both transmitter and receiver, and because of how the receiver works, it will very strongly reject anything which is not encoded with exactly the right PN sequence. (Or even anything which is encoded with that PN sequence but at a different phase.) The main reason our design in CDMA was more sophisticated than the original GPS system was that CDMA was designed later and the state of the art had improved. What we were doing required hardware in the receiver which wasn't technically possible when GPS was originally designed. This is important for CDMA because each phone operating on a given frequency looks like a jammer to all the others, but each phone uses a different PN sequence, so the ability to ignore any PN sequence except the one intended for you makes it so that your call will still get through to you. (I wrote an explanation of the basic concepts involved here.)
Go here for the rest of article.
Indeed they are. Send them a little HARM gift. Kind of expensive way to deal with a cheap jammer, but effective.
Sure, if you use really big antennas!
And it allows those of us in the Military Industrial Complex (formerly known as the Arsenal of Democracy) to keep paying our mortage and car payments, and putting food on the table. :) Besides that, it's fun!
EMP bombs in the first hour, JDAMS follow.
Disclaimer: Opinions posted on Free Republic are those of the individual posters and do not necessarily represent the opinion of Free Republic or its management. All materials posted herein are protected by copyright law and the exemption for fair use of copyrighted works.
