ABSTRACT The objectives were to: (1) survey the gamma radiation from fallout-contaminated ocean areas by means of aerial detectors and (2) from the aerial detectors make air-absorption measurements so that the data might be related to the dose rates at 3 feet above the sea. Radiation detectors were mounted in P2V-5 aircraft that surveyed the ocean areas of expected fallout after Shots Cherokee, Zuni, Flathead, Navajo, Mohawk, and Tewa. A control center coordinated all air and surface radiation-survey activities to insure complete coverage of the fallout area. The contamination densities in the delineated areas were related to the percentage of the total yield that produced fission products. Gamma-isodose plots were prepared from data obtained during Shots Zuni, Flathead, Navajo, and Tewa. No fallout could be located following Shot Cherokee and only on atoll islands after Shot Mohawk. Zuni, a land-surface shot, contaminated 13,400 naut mi’ of ocean with 48 percent of its fissionproduct yield. Navajo, a water-surface shot, contaminated 10,500 naut mi’ with 50 percent of the fissionproduct yield. After Flathead, another water-surface shot, the outer boundary could noted determined because of contamination of project aircraft on D + 1 day by airborne radioactive material that resulted in a high background. However, extrapolated values indicate 29 percent of its fission-product yield was present as fallout in the local area. The fallout from the watersurface shots was concentrated primarily in the more remote areas, anda relatively small amount fell close to ground zero. Tewa, a reef shot, contaminated 43,500 naut mi? of ocean with 28 percent of the fissionproduct yield. Helicopters and P2V-5 aircraft were used to gather data for air-absorption measurements. The aerial-survey technique may be used directly for radiological surveys over land. Over the sea, the depth of mixing of the fallout in the water volume must be determined before the Survey results may be converted to equivalent land-fallout contours and contamination-density distributions. Data on depth of mixing was obtained from samples of sea water collected by the U.S. Naval Radiological Defense Laboratory and the Scripps Institute of Oceanography. Repeated aerial surveys provided information on the stability of the contaminated volume. DOE ARCHIVES