0018933 “In cases where the stratum is not well defined, sample collections can be made from the top of the cloud provided this can be reached and followed by the sampling aircraft or from a location selected to minimize the feedein of fallout from higher altitudes, The theory of this technique has been discussed under section 1,2.4 and the sampling equipment is described in Chapter 2, The operation plan was to fly through the light and variable layer at several intervals between H £2 and H ¢/ 24 hours with B57D aircraft equipped both with the coincident samplers and with wing tank particle collectors, The coincident samples were to be analyzed for Kr88 and Mo?? to determine the fallout partition (see 1.2.4) and the wing tank samples for ten radionuclides to investigate fractionstion with particle size. 1.3.4 Aircraft Sampling of Fallout. The fallout sampling part of the program was intended to provide information supplementary to that obtained from the rocket and aircraft cloud sampling experiments, WB-50 aircraft were scheduled to fly at an altitude of 1000 feet and to collect fall- out at various times between H / 4 and H # 24 hours along height lines which would correspond to the cloud level (ca 55,000 feet) sampled by the B57D"s, Since the cloud is an extended source of fallout, the term "heightline sampling", as used here, signifies the sampling of a band of material centered on the geometrical height line and having a band width approxi- can BRE NO ER 37 37