The only US test of an operational ballistic missile with a live 600 kiloton warhead. A Polaris A2 missile was launched from the ballistic missile submarine Ethan Allen (SSBN-608) 2800 km east-northeast of Christmas Island. The re-entry vehicle reached the target zone 1890 km away and detonated at 3,300 m. The resulting mushroom cloud was observed by the submarines Carbonero (SS-337) and Medregal (SS-480), both stationed within 25 km of the predicted impact point.