from the vicinity of the Mike device to the control room aboard the USS Estes. For Mike Shot the master timing equipment was located on the shot island near zero. Radio controls were used to give manually started signals and to start the sequence timer. This same radio system could also be used to stop the shot at any time before zero time. The fol- lowing signals were sent by wires to the various experimenters: —30, ~15,-5, and -1 min; ~30, -15, ~5, and -1 sec. The earliest signal was sent manually, and all later signals were sent by cam-operated switches on a sequence timer. This timer was manually started at the proper time before the -15 min signal was due and ran throughits cycle automatically. Two independent television channels between the shot island and the ship were used for teleme- tering. The two cameras were focused on identical indicator panels, which showed the infor- mation required by the Firing Party Commander in determining whether or not the detonation would take place in an acceptable fashion. For King Shot, time signals were available at -30, -—15, and —5 min and at —30, -15, —5, ~2.5, and —1.5 sec. Zero time signals were furnished by individual Blue Boxes located near the equipment with which they were used. The first three signals were sent manually, and all later signals were sent from an automatic timer. This timer was started by a radio signal from the drop plane when the bomb was dropped. Manual signals were based on the estimated - bomb release time, and automatic signals were based on the time of fall of the bomb. Blue Boxes were triggered by the sharp rise in light from the explosion. With the exception of a number of Blue Boxes which failed to trigger on Mike Shot, this program can be considered highly successful. A complete photographic record of the Mike Shot television monitoring was obtained. 2.11. PROGRAM 11, PRELIMINARY GEOPHYSICAL AND MARINE SURVEY OF THE TEST AREA This program was designed to obtain detailed information as to the configuration and structure of Eniwetok Atoll in order that the effects of Mike Shot (and other high-yield shots presently planned for future tests) on that structure might be more readily and reliably interpreted. In addition, it included a study of the biological contamination effects resulting from atomic bursts near water. Prior to Mike Shot, both acoustic soundings and seismic-refraction surveys were conducted on and around the Eniwetok reef. Ground shock tests were accomplished in conjunction with HE detonations, and two deep-drill holes were sunk to unaltered basement rock. In addition, samples of marine life were collected both before and after the shot in order that the biological effects of radiation contamination might be subsequently analyzed in the laboratory. The only appropriate preliminary statement of results for this program is that usable data were recovered and are being reduced. Note: Later work has shown that the radiochemical yield results for Mike Shot quoted in Sec. 2.1 are too low. The reason for this ia that it has been found that the uranium content in coral varies markedly with coral depth. Since a considerable part of the uranium in post-shot debris came from associated coral, the resulting error was large. Although it has not been possible to make a good correction for the coral uranium contribution, a rough correction indicates that the radiochemical results are not inconsistent with te ball-of-fire yield, and the latter can_be considered to be correct. 14