Animation showing the evolution of interferences presence in the seas surrounding Japan between 2016 and the end of 2019

While checking for Patriot activity in South Korea I stumbled on the interesting increase of interferences in the seas surrounding Japan. This pushed me to investigate a little further to isolate the potential sources for them.

Hyūga class helicopter destroyers

The vessels (2) which became operational in the late first decade of 2000 saw the introduction of the indigenous ATECS (advanced technology command system) system and it’s main aerial radar, the FCS-3 .

FCS-3 is based on two different set of antennas, the first set operating in the C band used for surveillance and tracking and the second set operating in the X band for fire and control.

The C band antennas signals should be the ones causing the interference lines in the SENTINEL-1 data.

FCS-3 became the main aerial radar system for modern Japanese Maritime Self-Defense Force vessel.

JS Hyūga (DDH-181) is the lead ship of the Hyūga class helicopter destroyer of the Japan Maritime Self-Defense Force (JMSDF). Original source (wikipedia) Kaijō Jieitai CC BY 4.0

Akizuki class destroyers

The four vessels operational since late 2014 are meant as escort for the Hyuga class helicopter destroyers. All four employ ATECS and the FCS-3 radars.

Akizuki Class Fuyuzuki (DD-118) Original source Japan Maritime Self-Defense Force

Asahi class destroyers

Two vessels commissioned between March 2018 and late February 2019. The destroyers employ ATECS and the FCS-3 radars.

JS Asahi (DD-119) Original source (wikipedia) Hunini CC BY-SA 4.0

Izumo class helicopter destroyer

Two vessels commissioned between March 2015 and March 2017. They employ a version of FCS-3 lacking the X band fire and control antennas, but still have the C band ones.

DDH-181 Izumo Class helicopter destroyer. Original source (wikipedia) Kaijō Jieitai CC BY 4.0

Conclusions

Given the area where the interferences are detectable, the specs of the FCS-3 radars and it being installed on always more vessels, it is quite plausible that most if not all, interferences detected by SENTINEL-1 in the area are traceable back to vessels employing the modern Japanese radar.

If any reader knows of other C band radars operating in the around Japan please let me know, would love to keep this list updated with additional discoveries.

You can read more about SENTINEL-1 and how and why it can be used to track some military radars here.

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