It looked much closer than Johnston Island. The elevation of the circle was perhaps 20° above the horizon. Operation HARDTACK I Nuclear Events, 1958 Event Date Type Yield YUCCA 28 April High Altitude (Balloon) NA* Surface 18 kilotons CACTUS 6 May FIR 12 May Barge NA BUTTERNUT 12 May Barge NA KOA 13 May Surface WAHOO 16 May Underwater NA HOLLY 21 May Barge NA NUTMEG 22 May Barge NA YELLOWWOOD 26 May Barge NA MAGNOLIA 27 May Barge NA TOBACCO 30 May Barge NA SYCAMORE 31 May Barge NA 1.37 megatons ROSE 3 June Barge NA UMBRELLA 9 June Underwater NA MAPLE 11 June Barge NA ASPEN 15 June Barge NA WALNUT 15 June Barge NA LINDEN 18 June Barge NA REDWOOD 28 June Barge NA ELDER 28 June Barge NA OAK 29 June Barge HICKORY 29 June Barge NA SEQUOIA 2 July Barge NA CEDAR 3 July Barge NA DOGWOOD 6 July Barge NA * Not announced 120 8.9 megatons