(FLATHEAD) . Project 2.63 - Collection and characterization of Fallout with Time T. Triffet Obsectives To collect samples of fallout and measure radiation field intensit- ies with time at various distances from thermonuclear detonations. " land, water and air To study these samples from early times with respect to gamma and beta activity, to analyze them for chemical and radio= chemical composition and to determine certain of their physical properties, including distributions of particle sizes. Instrumentation dd Instrumentation for the= (FLATHEAD) was similar to that for the 3” aa “ —_ (CHEROKEE). yaGe39 was located approximately 30 miles, YAGw40 approximately 40 miles and LST-611 approximately 50 miles from ground zero; all, however, were at different azimuth angles. Results Approximately 95 percent of all project instrumentation functioned properly and no damage to any station from blast or thermal effects was observed, Within the Bikini complex the Chieerete station received no fallout, the Bikini station only very light fallout, the YFNB~29 moderate fallout, and the YFNB~13 and Aomoen station relatively heavy fallout. Add- itionally, Raft S and Skiffs AA, BB, and CC received small quantities. Collected samples averaged 400 mr/hr surface reading at 1400 on F-day, with some as high as 1.8 r/hr at the same time; the time of arrival at the YFNB-29 was about ] hour and 20 minutes after detonation. With the exception of the probe mounted on the boom of the YAG-40 all instruments aboard the three project ships were operated over the entire fallout period, Each ship received fallout, the approximate times of arr- ival being H # 44 hours for the YAG-39, H 4 7 hours for the LST-611, and POMEDIDGE WRG -~HRe os U .