OPERATION HARDTACK I - DATE: TIME: PPG Time 6 May 1998 0615 Cactus GMT Sponsor: 5 May 1958 1815 SITE: TOTAL YIELD: 18 kt LASL PPG - Eniwetok - Yvonne 11° 33' 23" N 162° 21' 15" E Site elevation: FIREBALL DATA: Time to lst minimum: 12 msec Time to 2nd maximum: 130 msec Radius at 2nd maximum: 656 ft HEIGHT OF BURST: Sea level 3 ft TYPE OF BURST AND PLACEMENT: Surface burst - Platform on coral soil CRATER DATA: Diameter: Depth: Lip Height: Lip Width: 340 ft 34.5 ft CLOUD TOP HEIGHT: 19,000 ft MSL CLOUD BOTTOM HeIGie: NM 8 to 14 ft 115 to 170 ft REMARKS: Only individual island dose rates are available. These were obtained from helicopter surveys at H+4 hours made by the Radiological Safety organization. The helicopter survey technique called for the pilot either to land the aircraft at the desired spot, so that a ground reading could be obtained, or to make a slow pass over the desired spot at an elevation of 25 feet. Readings taken at 25 feet were multiplied by a factor of © in order to obtain a reasonable approximation of the true ground reading. The basic instrument used in the aerial surveys was the AN/PDR- 39 survey meter modified to read up to 500 r/hr. The t-!+? decay approximation was used to extrapolate the H+ hour dose-rate readings to H+l hour. 189