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This test plan describes a technical aerial survey program of scientific photographic and gamma radiation measurements for selected islands in the Eniwetok atoll chain and priorities for carrying out these measurements. These surveys will be conducted in a time frame beginning 4 November 1972 and ending on or before 23 November 1972. Two CH-53 helicopters, flown by the 36th Marine Aviation Group, will provide the aerial platform for these measurements. The following list of tasks is arranged in order of priority in the event that the helicopters are severely limited in operation or weather causes Tasks in Descending Priority Vertical aerial photographs will be taken of all islands in the entire atoll. Four Hasselblad cameras will be operated simultaneously; two with black and white film and two with infrared black and white film. Of the four films, two will be processed on island for immediate use. The remaining two will be returned to the mainland for controlled processing. The attached table indicates planned photographic coverage. {4 hrs, 2 flights)
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Tasks in Descending Priority (cent) 9“. Initial Gamma Radiation Survey Gamma radiation survey of three islands, This survey will consist of a cross-hatched grid of flight lines spaced 150 feet apart. Sets of parallel flight lines will be flown perpendicular to each other. Two surveys will be flown for each island to record gamma energies consistent with cobalt (O to 3.0 MeV) and americium (O to 300 keV). (6 hrs, 2 flights) Four camera multispectral photographic survey of all islands in the entire atoll to include the following four wavelength bands: d. IR black and white (Kodak Infrared) This survey will be flown as lighting and cloud cover permit. 4. Complete _Gamma Radiation Survey Gamma radiation survey of remaining islandsEach island will be surveyed with a cross-hatched grid. Two grids will be flown for each island, 1) for cobalt and cesium (O to 3. 0 MeV), and 2) for americium
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Tasks in Descending Priority (cent) Flying Hours (O to 300 keV). The order in which islands will be surveyed is the following: a. A contingency flight path to ring the entire atoll centered on each island
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Tasks in Descending Priority (cent) 5. Reef Gamma Radiation Survey On a low priority basis, the reef below Alice will be surveyed at low tide. 6. Special Request and Documentary Photography Includes search for underwater objects such as the MACK tower. (Photos may penetrate to depths of ZO feet. ) Also includes oblique still photographs and 16mm color movies of the survey operation. Presentation of Information Photographic processing and printing capability and computer data processing capability for the gamma radiation data will be available on Eniwetok during the survey. Six photo books will be prepared on the isIand for black and white quick-look records. These books will provide technical management personnel with an up-to-date aerial map of Eniwetok atoll. of photos will be used by the gamma radiation survey team gation purposes and overlay presentation of survey data.
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Gamma radiation data will be processed immediately after each flight. Total processing of data from any given flight may require one to two days to complete. Overlays will be prepared in a scale compatible with the photographs. Data will be displayed as exposure rates for an equivalent three foot above ground measurement (uR/hr or mR/hr as appropriate).
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PLANNED PHOTOGRAPHIC COVERAGE OF ISLANDS IN ENIWETOK ATOLL Island Aircraft Coverage On Size Altitude No. Of No. of Ground Connected to Yvonne
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Spatial resolution is controlled by altitude, flight speed, data accumulation time and gamma-ray energy. The detectors exhibit a cosine angular response for low energy gamma-rays such as the 60 keV line from Am 241. Inherent spatial resolution is approximately 125 ft at 100 ft altitude for this energy. Inherent spatial resolution is degraded for higher energy gamma-rays due to the decrease in air attenuation and the transmission of gamma-rays by the shielding around the sides of the crystals. The assumption of isotopic angular response and no air attenuation for high energy gamma-rays gives a spatial resolution of 200 ft at an altitude of 100 ft. Data accumulation time can be adjusted to be consistent with inherent spatial resolution and flight speed. Sensitivity is controlled by survey rate, spatial resolution and background count rates under the photopeaks of interest. Sensitivities can be estimated by assuming background spectra in the region of interest to be identical to that taken over typical U. S. Soil with an array of 4- by 4-inch crystals. Amplitude of the spectra are scaled according to crystal surface area and radiation levels three feet above the ground. The following sensitivities are estimated with these assumptions and the additional assumptions of 100 ftlsec flight speed, spatial resolution of 150 ft, survey speed 15000 f~ /see, and cosine angular response for the detector system
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