How Iran Acquired A Stealth Drone

Moon of Alabama | December 5, 2011

It seems that Iran has acquired a U.S. stealth drone which was illegally flying within its airspace.

A secret U.S. surveillance drone that went missing last week in western Afghanistan appears to have crashed in Iran, in what may be the first case of such an aircraft ending up in the hands of an adversary.Iran’s news agencies asserted that the nation’s defense forces brought down the drone, which the Iranian reports said was an RQ-170 stealth aircraft. It is designed to penetrate enemy air defenses that could see and possibly shoot down less-sophisticated Predator and Reaper drones.
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U.S. officials acknowledged Sunday that a drone had been lost near the Iranian border, but they declined to say what kind of aircraft was missing.
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The first reports of the drone crash came from Iran’s semiofficial Fars News Agency. “Iran’s army has downed an intruding RQ-170 American drone in eastern Iran,” the Arabic-language al-Alam state television network quoted an unnamed source as saying. “The spy drone, which has been downed with little damage, was seized by the armed forces.”

Reuters wrote that a U.S. official says there is no sign Iran shot down the drone. Of course Iran never claimed that it shot it down so this is a non-denial. Iran just “downed” the drone by some electronic warfare means.

The question now is “How did they do it?” Here are my speculative ideas on that.

As this is a stealth drone detecting it is the first problem. A usual monostatic radar where the emitter of the radar beam and the receiver which catches the echo from the airplane are in the same place would not find the drone. The drone’s form and its echo reducing coating would scatter the beam too much.

But by using bistatic radar where the emitter is separated from the receiver(s) by a distance that is comparable to the expected target distance even stealthy flying objects can be detected.

Detection by electronic means is also possible if the drone is receiving and sending information via its satellite link and not just silently following a preprogrammed flightpath. While the signal from the drone to the satellite is sent in a highly directional beam, a plane equipped with the necessary radios flying above the drone and near the line of sight between the satellite and the drone should be able to locate it. If the drone used its own radar to “look around” the recently delivered Russian Avtobaza “anti-stealth” system will likely have detected it.

The Iranians say it did not shoot the drone down but “downed” it with little damage. I think they may have actually landed it.

This RQ-170 drone type became known as the “Beast of Kandahar” when it was first observed there four years ago. Flying U.S. stealth drones in Afghanistan is obvioulsy necessary to escape the Taliban’s radars (not). The drone is quite big with an estimated wingspan of 65 feet (20m) to 90 feet (27m) and a takeoff weight of some 10,000 lbs.

When the drone is in the air it is controlled via a satellite link from a remote operating station. But during start and landing the drone is piloted via line-of-sight radio by an operator near the start or landing field. This is necessary because the remote satellite link has a delay of several hundred milliseconds which is just too much latency to correct wind sheer and other problems during takeoff and landing.

What the Iranians seem to have done is to take over the drone’s line-of-sight control. This after electronically disrupting its satellite link. Disrupting the satellite link alone would not be enough as the drone would then have followed some preprogrammed action like simply flying back to where it came from. With the line-of-sight control active a satellite link disruption would not lead to a preprogrammed abort.

We can reasonably assume that the Iranians have some station near Kandahar Airport that is listening to all military radio traffic there. They had four years to analyze the radio signaling between the ground operator and such drones. Even if that control signal is encrypted pattern recognition, during many flights over four years would have given them enough information to break the code.

Iran will take care to hide the drone well as the U.S. would likely try to destroy it if its location would become known. When the Chinese collected parts of a stealth F-117 stealth plane that was downed in Yugoslavia the U.S. bombed their embassy in Belgrade.

Having acquired an only slightly damaged state of the art stealth drone Iran will be able to copy a lot of its technology as well as to find new measures against such drones. There will also bee a lot of interest from other sides into this technology. We can bet that the military attaches from the Russian, Chinese, Indian, Pakistani and other embassies are already queuing up in the Iranian Defense Ministry and ready to make some very lucrative offers.

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