Friday, September 09, 2011


South Korean political sources say a U.S. reconnaissance aircraft was forced to make an emergency landing on the peninsula earlier this year, after extensive jamming from North Korea.

An unnamed official told AFP that the incident occurred on the afternoon of 4 March, about 45 minutes into its mission. The U.S. aircraft received jamming at five to 10 minute intervals which interferred with its GPS system, forcing it to return to base.

[An] aide [to the ROK Parliament Defense Committee] aid the plane suffered disturbance to its GPS system due to jamming signals from the North's southwestern cities of Haeju and Kaesong as it was taking part in the annual US-South Korea drill, Key Resolve.

The incident was disclosed in a report that Seoul's defense ministry submitted to Ahn Kyu-baek of parliament's defense committee, the aide to Ahn said.

Spokesmen for the defense ministry and US Forces Korea declined to comment..

The jamming also reportedly affected South Korean patrol boats in the Yellow Sea and civilian air traffic operating from Kimpo Airport near Seoul.

This incident is significant for a couple of reasons; first, jamming is considered an act of war, and could have resulted in an armed response by the U.S. or South Korea, if either country was so inclined. But, given the collective willingness of Washington and Seoul to ignore such provocations as last year's sinking of a ROK corvette, and the shelling of a South Korean island near the DPRK coast, Pyongyang figured they had nothing to lose, and once again, they were right.

The jamming also suggests that North Korea has upgraded its modest electronic warfare capabilities. While GPS jammers have been on the arms market for a number of years, Pyongyang's capabilities in this area were limited. If the report is accurate, the DPRK may have acquired a more powerful GPS jammer, capable of affecting navigation systems over a wider area, (potentially) impacting a host of activities, from intelligence collection to precision weapons applications.

Note the use of the term "potential." That's because we have some counter-measures for GPS jamming that can lessen its impact on the battlefield. Needless to say, we weren't going to demonstrate those capabilities during Key Resolve or any other routine exercise. So, North Korea can keep guessing about the effectiveness (and survivability) of its GPS jammers in a combat environment.

While the type of aircraft involved in the incident was not disclosed, it was probably an RC-12 Guardrail; an RC-7 ARL (Airborne Reconnaissance Low), or a U-2. All three aircraft can collect various forms of intelligence, and none have an on-board navigator. Relying on GPS data for everything from flight navigation to sensor slewing, the presence of heavy jamming would be enough to force the pilot or aircrew to abort the mission. Not only would the interference make some intel collection more difficult, it would also increase flight safety risks.

By comparison, other intel platforms (notably the Air Force RC-135 and Navy EP-3) have on-board navigators, allowing them to continue operations in the face of GPS jamming. However, the electronic noise would have some impact on intel collection by those aircraft as well--but probably not enough to force mission termination.

Still, the AFP report should be taken with a grain of salt, since it came from political sources. "Jamming" might be something of a cover term for something more sinister, like the illumination of a U.S. recce aircraft by a North Korean SA-5 site. The long-range SAM system poses virtually no threat to fighter aircraft, but it is capable of engaging reconnaissance, battle management and other support platforms at long range. Being "painted" by an SA-5 radar for an extended period would be sufficient grounds to terminate a recce mission, given the platform's potential vulnerability to that system.

On the other hand, if it was GPS jamming, such activity might be considered the prelude to an attack by some sort of air defense system, including the SA-5. That scenario provided even more reasons to end that March mission

However, activity from North Korea's two SA-5 complexes is extremely rare, and there has been some debate about their operational status. Without more details, analysts can only speculate about the time of interference that forced our recce platform to cut short its flight.


J.R. said...

I love GPS jammers. The enemy puts a big fat RF emitter right where he doesn't want you to bomb him. It's like your division rival sending out a QB with a bullseye painted on his sore leg.

Alaska Paul said...

Why did we have to end the mission because our GPS signals were jammed? Don't we have an alternative, such as inertial navigation.

This seems to show a major weakness in our capabilities. Or did we make an emergency landing to draw attention to the jamming?

TOF said...

They have been jamming the electronic spectrum routinely for decades. I recall exactly that during the Pueblo taking. My brother told me of false navigation signals and air traffic instructions on flight from Iwakuni to Seoul.

Jim Howard said...

My experience in Korean flying pre-dates gps, but in those days any flight in the buffer zone between the two Koreas required an immediate abort if there was any doubt as to the aircraft's exact position.

Some of the newspapers made it sound like the aircraft was hit by some kind of death ray that damaged the airplane.

I'm sure that's false.

A much more likely reason is that the mission rules required an abort if the gps became unavailable due to jamming or malfunction.