 The bomb was detonated 4000 m above the Sukhoy Nos ("Dry Nose") cape of Severny Island, Novaya Zemlya, from Mityushikha Bay, north of Matochkin Strait.The detonation was secret but was detected by US Intelligence agencies.The US apparently had an instrumented KC-135R aircraft (Operation "SpeedLight") in the area of the test – close enough to have been scorched by the blast.