Japan's radar did not detect Chinese Y-12 flying over Diaoyu Island.
Japan's expensive radar array aimed at Chinese aircraft.
Coverage of Janpan's X band radar, in theory....
Japan's FPS-5 radar array, will detect anything coming out of China, in theory....
Japan's long range missile monitoring radar array.
Y12 flew in from due south without being detected by any of the aboved mentioned radar system.
Y12 was hovering above the island 60 m from the sea level