, _ — Specitic RastriciadsSene-clearancesRequiret™ Explanation of Photographs Although many feet of film were used during Operation SANDSTONE to photograph tha atomic clouis, vary few pictures suitable for a scientific report on the clouds resulted. Since H-hour was before daylight, and because the atomic clouds had become sqmethat diffused by the tine sufficient Light became available, most photographs of the weapon phanomwena show only the hemispherical condensation clouds or the fireballs. Most of the film used for the clouds wis so completely underexposed that it printed completely black. The resuits fron the IRAY Day cloud were very disappointing to photographers who had hoped to obtain pictures of the spectac- ular masbroom. Fewer pictures of the YOK Dey cloud were attempted, and almost none were made of tha ZEBRA Day cloud. When sunlight for photographs was available, the clouds were being dispersed; and the photographers did not make mny pictures of cloud shapes which to them did not seem sufficiently well defined to be of Intorest, After two or threes hours the clouds bed many characteristics of mtural clouds, eo that to an minforned cbeerver, they did not appear to be particularly significant. dnother feature of the atomic clouds which was discouraging to photographic personnel was that as the clouds dispersed, the cloud material extended over such a large area that it was impossalble to frame all of a particular cloud in a single photograph. No camera had a wide-angle lens suitable for such a large coverage, and there was no attempt to adapt a camera for terles of panoramic views. In assenbling pictures for this report, two photographs have been joined side by slide if they give a more compliste representation of a cloud even though the two photographs may have been made at slightly different times. It hea not been feesible to make neagurements of the clouda directly from the photographs. This ie primariiy because the distances to the clouds are not sufficiently well determined, It 18 such easier to mike measurements fran the theodolite data and the sketches than to use the photographs, Such data as are available from the calculations on the preceding mges Inve been added to the photographs. that the diagram titled Tha shape of the top of the TRAY Day cloud we such on page 35 could be used A few colored photographs of different views of each ofthe atomic olouds exint, but the type of printing facilities available prevented the use of color in this report, However, the colors of the clouds will be described as the photographs of each test are discussed below. XRAY DAY-Excopt for not showing the colors of the cloud, these photographs give 5 reasonably good portrayal of tha cloud up to H-hour plus three hours. With this cloud as well as the other two clouds, the coloration was largely determined by the amount of sunlight available. After the blue-violet of thea luminescence faded, about three or four minutes after H-hour, tha clowl appeared to be a dnl white, while the naturel comilus appeared a dirty grey. At about H-hour plus ten minutes, the upper part of the TRAY Day cloud appeared white and the lower portion had a dirty, smoky color. Than at H-hour plus twenty ainutes wtil H-hour plus thirty minutes, the upper portion of tha cloud took on the wiwid colors of the sunrise, ‘The east side of the mushroom became a brilliant reddish-orange, while the remainder of the clowl remelned a dull white, 4a ths sun rose higher, this coloration apread over the cloud and be- came less brilliant. The cirrus-type pluse sleaye appeared much whiter than the pri- mary cloud, and showed up vividly against the background of dark blue aky. In direct sunlight, the globular mass bad a cream colored appearance when contrasted to the intense white of the cirrus plums or to natural cirrus. Even when the'top had spread until it greatly resembled natural cirrocomulus, the slight coloration was noticeable. The lower portion of the IRAY Day cloud, which appeared to conaist of aacke and dust, had a distinct reddish-browm color that persisted as long as it could be seen, YOKE DAY-aithongh photographs of this cloud from the surface were not possible until about H-hour plus 35 minutes, cameras in aircraft, sbere the cloud uaa silhouetted against the light in the eestern sky, gave usable pictures as early as H+hour plus 15 minutes, to obtain « rough idea of ita djameter, tut the simpe of the TOKE Dey cloud ws such that this type of dispersion analysis was not applicable. No pictures of the ZEBRA Day cloud are available wtil about H-hour plus 45 sinntes, 15 minutes after the tine that it became necessary to end the apparent dispersion analysis because of the poor quality of the aximuth angle data. There is no my of adding dimensions to the primary mass to the photographs of the ZEBRA Day cloud except by mean’ of the upper winl Tbe photograph of this cloud on page 68 does not show the shape of the cloud as well as would be desired, but a color photograph mide at the came tine shows the detaile clearly, The color photograph bas been used to make a sketch of this cloud. This eketch ie presented on page 50, ture on the shape of the cloud are shown on page 42. However, the lengths and widths of the TRAY and YOKE Dey clouds have been entered on photographs made one hcur past H-hour. These data bare been determined from the estimated winds and the diagrams and then into a yellowish cream color. The color of the stem of the cloud was the reddish-brown color of the saoke and dust of which it consisted, At about B-hour plus one hour, the time that the photograph on page 68 was made, the stem appeared vectors, and this does not seem to be worthwhile since the effects of the wind struc- titled Clouds Hours. Where altitude dita are given, 5,000 foot intervals are used in most cases because the wind deta selected for detersining the shapes of the clonda were for 5,000 foot olevations my. At about fifteen minutes just after H-hour, the rising sm colored this cloud a dark reddish-orange. After that time, the orange faded into a dirty-yellow reddish-brom even io direct eumlight, The top portion of the cloud, between 35,000 ani 55,000 feet, appeared as a broad band of clrrocumlus, and ms alecet white. ZEBRA DAY-is fer es 18 know, there are no original black and white photo- A better umerstamding of the shapes and sizes of all of the atomic clouis 4s obtainable by using the photographs in conjunction sith the diagrams titled graphs of the ZEBRA Day cloud, The quality of the majority of the cloud photographs included here ia poor, Very few of the pictures lave contrasts euitable for half-tome reproduction, and many of the detaile which were evident in the original photographs were lost in printing, reddish-brown that had been seen in the etems af the previous atomic clouds, There seemed to be little or no moisture to give whitenesa to any part of this cloud, CloudsHours, beginning on page 39. from colored prints, The pictures on peges 69 and 70 have been reproduced When the em show on the ZEERA Day cloud, the entire cloud was the sane 4 '