OPERATION HARDTACK I - DATE: TIME: PPG Time 11 June 1956 0530 Maple GMT Sponsor: 10 June 1958 1730 SITE: UCRL PPG - Bikini - South of Fox 17° kit 165° 2kt ws" su" Site elevation: HEIGHT OF BURST: N E Sea level 11.58 ft TYPE OF BURST AND PLACEMENT: Surface burst from barge on water CLOUD TOP HEIGHT: 40,000 ft MSL CLOUD BOTTOM HEIGHT: 1M REMARKS: Only individual island dose rates are available. These were obtained from Radiological Safety organization helicopter surveys at H+4 hours. 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 2 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 t7°® decay approximation was used to extrapolate the H+4 hour dose-rate readings to H+tl hour. 242