extremely Linited, complete documentation of this type burst being confined to we low yield shot at the NPG. The cnly high yield surface shot (IVY MIX® at the PPG) had nct been documented except on the shot atoll itself. C.cTIS Radsafe planning wae based on the information from these two shcts. & the basis of CASTLE raifation measurements, the assignment of actual in= tensity valuss to long-range forecast fall-out patterns for high yield shots e:m now be done with a great deal ‘nore conflience. (f) IVY MIKE eerly crosewind and upwind iso-intensity valucr scaled to a chart of BIXINT atoll reasonably representad (with allowances f-y yiold nd shot conditions) the values observed close-in on C.STLE. Also, a new techrique Jevoloped to determine the initial distribution mathanati- cally was used to some extent and success ca the latter part of the series. (g) The assumption 2f a cireular source of lS-aile radius was adequate for the water surface shots, For the land surface shot, the radius is estimated to have been on the orier of 25 miles. <lthough the true source was assumed to be elliptical with major and aincr axes in 4 ratio of 2:1 to 3:1, a cdreular sector adequately deacribed the upwind and crosse— wind spread. (h) Computed surface R.DEMES required a factor of safety applied to the forecast regiondue to errors in the wind forecast, diffusion of the elowd, initial sise of the cloud sourss and changes in the wind pattern in areas cutside the influence of ground sero winds. Om C..STLE the aiditica of a fifteen-degree sector on either side of tha computed area was adequate for this purpose, (4) The effect of yield versus crosewind ami upwind spread of contamination over the shot atcll was such that, fram a fall-out viewpoint J2