i _ ee tests since Ivy we have reasonable confid- ence in our factors of altitudes so that we really feel we can measure radiation from an aircraft and within reasonable limits Giving you the figure that you have on the surface. Recentiy we have had other peovle working on this problem and they have come up eccentially with the seme information. The only way you can know what it: is on the ground is to vary your altitude and if it stays pretty constant you know what 4t is, DR. BRUES:: Does it compensate the factor very, very mich? MR. CASSIDY: TI don't think it is. The compensating factor falls in very well, This is one of the big problems we have} _ this ie sort of an uncertainty and this is ' gomething that we have got to pin down some day about just hy we are able to take these measurements over a long period of time al-= though sources of widely varying shapes and densities and sizes can still come out with a factor, thet is fairly constant cver these altitudes, is

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