—— A VOICE: 15 How cloce would your numbers compare in. the air from those that are measured on the ground at the ground at the same time. Hseve you tried that aa a control? How close are the ground readings with the air readings at the same time? MR. CASSIDY: determine the factors. Thisis how we We take a measure- ment on the surface and then we fly above it. e MR. EISENBUD: It's ae close as independent ground readings would be. MR. LEVINE: You might give the figures where you have your aerial and your ground readings at the came time. MR. CASSIDY: Yes, but thet is actually how we did determine it. There 416 a spread in data of snbout twenty per cent. The big problem of getting this factor of measuring from the air is not so much the inaccuracy of radiation data but the inaccuracy of the altimeter. Until we got that radar alti- meter, we had gone all over the 10%.. \ a \ \

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