3D Robotics


[I'm applying the sysadmin privilage of making an exception to our usual no-military rule here, because the technical issues are sufficiently interesting].

Apply the usual skepticism about the claims, but there's something plausible in the following. As I understand it, the assertion is that Iran basically used radio jamming techniques to force the RQ-170 into RTL mode, then overrode the GPS signal with a fake one that made it think that "home" was an Iranian field. 

An excerpt from the Christian Science Monitor, a good article that discusses what may have caused the capture:

Iran guided the CIA's "lost" stealth drone to an intact landing inside hostile territory by exploiting a navigational weakness long-known to the US military, according to an Iranian engineer now working on the captured drone's systems inside Iran.

Iranian electronic warfare specialists were able to cut off communications links of the American bat-wing RQ-170 Sentinel, says the engineer, who works for one of many Iranian miltiary and civilian teams currently trying to unravel the drone’s stealth and intelligence secrets, and who could not be named for his safety.

Using knowledge gleaned from previous downed American drones and a technique proudly claimed by Iranian commanders in September, the Iranian specialists then reconfigured the drone's GPS coordinates to make it land in Iran at what the drone thought was its actual home base in Afghanistan.


"GPS signals are weak and can be easily outpunched [overridden] by poorly controlled signals from television towers, devices such as laptops and MP3 players, or even mobile satellite services," Andrew Dempster, a professor from the University of New South Wales School of Surveying and Spatial Information Systems, told a March conference on GPS vulnerability in Australia.

"This is not only a significant hazard for military, industrial, and civilian transport and communication systems, but criminals have worked out how they can jam GPS," he says.

The US military has sought for years to fortify or find alternatives to the GPS system of satellites, which are used for both military and civilian purposes. In 2003, a “Vulnerability Assessment Team” at Los Alamos National Laboratory published research explaining how weak GPS signals were easily overwhelmed with a stronger local signal.

“A more pernicious attack involves feeding the GPS receiver fake GPS signals so that it believes it is located somewhere in space and time that it is not,” reads the Los Alamos report. “In a sophisticated spoofing attack, the adversary would send a false signal reporting the moving target’s true position and then gradually walk the target to a false position.”

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  • T3

    Hi Andy Cross,

    Wow, I was just looking at the specs for a Ring Laser Gyro based Sperry Marine Inertial Navigation System. It has 1 nm accuracy in 8 hours, without GPS.

    Best regards,


  • Hi Chris

    You make a good point but for most passenger and military aircraft today do not rely on just one GPS feed, they will take typically 3 feeds (a voting sytem) and one of them will be a Inertial Navigation System (aka Ring Laser Gyro RLG), the primary will be GPS but if any reason it fails of more likely there is a large discrepancy, one of the other two sources becomes the primary, so the jamming idea although feasible is unlikely. That's my take.

  • Developer

    We all know that the UAV came down because of an malfunction. So the question is, did Iranians cause the malfunction to happen? If they did, electronically it could be as simple as the UAV for some reason not entering RTH mode when getting jammed (military engineering is by no means flawless just like civilian engineering). Or for all we know, they could have shot it down by conventional means.

  • Yeah to add - at sounded to me early on in this debacle that Iran was using Russian jamming tech to bring her down, or that there was russian tech and know how involved in this procedure. But not as worrying as what they found on board - aerosol distribution capabilities, and this two weeks after a lab in the US annonced that in five mutations of the H1N1 virus they have now created the most dangerous virus ever. (I support non military related posts on diy drones FYI)

  • Well, its flying days are over thats for sure - and its not like china doesnt know every dirty little technological secret the US has ever had, and to further illustrate my point - a week ago china declared its intentions (Or rather, lack of inhibitions to enter such an horrific scenario as no problem!) to enter world war 3 with Russia, N. Korea and Iran should Iran be attacked or treated unjustly. And  on top of htat you have america biting at the bit to go ahead and waste those bastards in tehran so yay for the military industrial complex and its necessity for war.

  • The Greeks dedicate this thank-offering to Athena for their return home.”  Clever. 

  • @chris unless with eternal help, would mirror @jasonshort view on P code for GPS afaik
  • Developer

    Some informations about military GPS channel L2 :

    1) It is not necessary to crack the L2 GPS military channel to take advantage of its positionnal precision. In fact civil Survey L1 - L2 GPS are using (expensive and protected) code developed by a group of GPS manufacturers to allow partial "reading" of the military L2 channel and get the added precision.

    2) I suppose that if you can scramble the GPS L2 channel with a strong local signal, then a military GPS receiver will revert to L1 only decoding. Then in this case it is possible to fake the GPS L1 channel signal using satellites or planes with highly directional antennas, sending strong signal to replace the normal L1 signals. Nevertheless this is a very hightech and difficult attack, i doubt it would be done simply to get an UAV.

  • T3


    It is not possible to remotely interfere with a magnetic compass. You have to get within a few feet to do that.

    Also, the military drones use high quality gyros. They are not drifty. For more information, I suggest the

    Aviation Week Article .

    Best regards,


  • Regarding fusing the IMU data with the GPS, if the gyro is fused with compass data, they could potentially use magnetic interference to support the GPS data and by turning the plane's heading at a slow enough rate, the gyro data might be overruled by the GPS and compass.

    That would assume they use a drifty gyro and compensate with a magnetometer though. Another way to prevent this though: http://en.wikipedia.org/wiki/TERCOM

    This is a failure mode and effects analysis game.

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