principal objective was to attempt to confirm phenomena observed in the F2 layer during Shot Mike of Ivy, both in the general vicinity and at a great distance from the shots, in order to learn more about the to carry out their missions in the event of transit through contaminated fallout, (2) significant attenua- tion is afforded by ships structures, (3) decontamination procedures require further development, and (4) there is negligible hazard contributed by boiler air, or ventilation systems with fans turned off. ionosphere and to help determine possible military applications such as long-range detection. Two ionosphere recorders were operated in the Project 6.5 “Decontamination and Protection” Marshall Islands by project personnel: one at Parry Island, approximately 200 miles west of the Bikini (WT-928), Chemical and Radiological Laboratories, Army Chemical Center; J. G. Maloney, Project Officer. The primary objectives were to: (1) determine the relative contaminability and decontaminability of conventional building construction materials when ex-~ posed to the type of wet-contaminantfallout which would be characteristic of nuclear detonations in shots (23 miles from the shot at Eniwetok), and one at Rongerik Atoll, approximately 150 miles east of the Bikini shots (350 miles east of the shot at Eniwetok). At Guam and Okinawa (about 1,400 and 2,600 miles from Bikini, respectively), lonosphere stations, regularly operating as part of the world-wide system, furnished special data to this project at times bearing a specified relationship to each shot time. When oscillograms from the ionosphere recorders are properly analyzed, they give data on the height and critical frequency (a function of the maximum ion density) of each observable ionosphertc layer. harbors, (2) ascertain the relative effectiveness of various decontamination techniques, and (3) determine the need for pre-attack protection measures in reducing contaminability and/or facilitating decontamination. Fourteen 4-foot-square panels with different types of outside construction surfaces were mounted on On Castle, frequent records (up to four per minute) (YAG-40) which were operated through the fallout were obtained with these recorders following each detonation, the timing program varying according to the location and operational conditions. Through- of panels was mounted on board the unprotected ship five times an hour to establish normal conditions for (YAG-40). For Shot 6, another identical set of panels was mounted on board a barge moored in the fallout area. Subsequent to contamination, the panels were removed to shore, monitored for contamination intensity, and then subjected to decontamination efforts utilizing a variety of hosing and scrubbing techniques. The salt water washdown appeared to be effective in minimizing contamination of construction surfaces under the conditions of Shot 2. The contamination resulting from Shots 2 and 4 comparison. beth a drone, washdown-protected Liberty ship (YAG~39) and an unprotected drone Liberty ship area following Shot 2. For Shot 4, an identical set was very tenacious in nature and was much more out the operation, regular recordings were made A tremendous amount of absorption (and possibly scattering) followed all shots, particularly those of higher yields, causing obscuration of the F2 layer for several hours at the Rongerik station and longer at the Parry Island station. However, enough data were obtained at Rongerik to indicate that for shots of megaton yield range an effect occurred which was similar to the rising-F2-layer phenomenon observed difficult to remove than the contamination encountered in Jangle. A great difference existed among the construction surfaces with regard to initial contamination levels and ease of removal; of the methods employed, the hand-scrubbing technique was the mosteffective. Under the conditions of those shots contaminating the YAG’s, vertical surfaces became generally more highly contaminated than horizontal and sloped surfaces: this was probably caused by the horizontal after Shot Mike of Ivy. Variations were noted between results of one shot and another which may have been due to different yields or different fonospheric conditions. The Parry Island operation, though hampered, re- sulted in a new hypothesis to explain the protracted absorption that may prove significant. It suggests that the absorption occurring at Parry Island several houra after the shots at Bikini (200 miles to the east) was a result of :opious ionization overhead, caused by beta particles and radioactive particles carried westward by winds at 60,000- to 120,000-foot levels. Records from distant stations indicated that ton- wind components across the deck. ospheric disturbance resulted from megaton detonations at ranges up to 2,600 miles. Project 6.6 “Effects of Nuclear Detonation on the Signal Corps Engineering Laboratories; Fred B. Daniels, Project Officer. Ionosphere recorders were operated both in the Marshall Islands and at distant locations to study PROGRAM 7: LONG RANGE DETECTION PROGRAM the effects of the test detonations on the ionosphere, Particularly on the F2 layer (the highest portion of the ionosphere, from about 200 km upwards). These disturbances apparently propagated outward from their origin at a velocity of 8 to 16 km/min. Ionosphere” (WT-929), Evans Signal Laboratory, Project 7.1 “Electromagnetic Radiation Calibra- The 115