AOC. Air Operations Contro} Center. AQG. Gasoline tanker. AP, Transport ship. APG, Aberdeen Proving Ground, Maryland. ARA. Allied Researcn Associates, Baston, Massachusetts. ARS. Salvage snip. ARSD. Salvage lifting ship. ASA. Army Security Agency. ASU. Army Support Unit ASW. Anti-Submarine Warfare. ATA. Auxiliary ocean tug. ATCOM. ATF. Atoll commander. Fleet ocean tug. atoll. A ring of coral reefs, usually with small islets, that surrounds a lagoon. Most are isolated reefs rising from the deep sea that nave built up on submerged volcanoes. They vary considerably in size; the largest atoll, Kwajalein in the Marshall Islands, has an trreqular shape that extends for 84 miles (135 km). See also coral reef. atomic bomb (or weapon). A term sometimes applied to a nuclear weapon utilizing fission energy only. also fission, nuclear device. atomic exolosion. See See nuclear explosion. attenuation. The process by which radiation is reduced in intensity when passing through some material. It is due to absorption or scattering or both, but it excludes the decrease of intensity with distance from the source (inverse square law), which see. AU. Army Unit. AV. Seaplane tender. AVR. Aircraft rescue vessel. AW. Distilling ship. B-29. A 4-engine, propeller-driven bomber developed by Boeing, used for weather reconnaissance, cloud tracking, aerial sampling and photography, and aerial refueling at the PPG. These versions desig- nated RB-29, WB-29, and K8-29. B-36. A long-range, strategic bomber powered by six pusher propeller engines, supplemented by Four jet engines. Developed by Consalidated Aircraft. Used as the subject of effects experiments and as a sampler controller aircraft. Also designated FB-36, RB-36, and WB-36. 8-47. A 6-jet-engine bomber with sweptback wings and a double-wheel bicycle landing gear, developed by Boeing. Used as the subject of effects experiments. 8-50. B-57. A 4-engine bomber developed by Boeing, with some features like those of the B-29, but havirg a taller tail fin and larger engines and nacelles. U.S. version of English Electric Canberra bomber used as cloud sampling aircraft. background radiation. The radiation of man's natural environment, consisting of that which comes from cosmic rays and from the naturally radioactive elements of the Earth, including that from within man's body. The term may also mean radiation extraneous to an experiment. barge. A floating platform used as the support for the cab, or shelter, "ng prepared for testing. 472 in which nuc’ear devices were be-