cloud sempling aircraft operating during the same period, and was die~ seminated for the purpose of assisting these aircraft in finding the best sampling srea. In general, tha construction of tn2 air RDEX consisted of selecting an altitude at the bottom of the vile under consideration, considering this altitude as a surface, and constructing a hodograph oy this "quasi-surface" using appropriate winis above tne surface. Cone taminated areas were then defined by the use of diffusion factors applied time-wise to the resultant winds obtained, and modified te account for deviation fram = point source origin of fall-out. The air ROEX wes also issued for a valid period of H to H plus 6 hours, fevised as neceseary, and disseminated to all test personnel with particular attentiat to its availability and use by the (ir Operations Canter, (0) New Teghniquee: J. new techrique te define the close-in fali-cut was developed to explain the shot atoll phencaaitt, and was wed partisularly to evaluate tho foresast effects oS MECRAR on the DHIWETOK samp site, (Ses Incl 3 of Tab 5D). ‘This nethad, in general, employs « methematical approach to the initial close-in distribution of fall-cut, (3) Pall-cut Plots: (a) The primary fall-out plot technique planned and initially used om C)STLE involved « jciut amilysis of the surface RDEE and the 72-hour air particle trajestory fcresast to define the ares of the first twelve-hour period of fall-out, end to formilate some opinion as to the crplentation and extent of the area inwlved cubsequent to the first twelve hours. Por BR:VO an attexpt ws made to employ the method of 67