Instrumentation The principal collecting instruments of each platform were four Open- close Collectors (OCC) and two Always-Open Collectors (AOC;) located in the periphery area. These two types of instruments have similar collecting characteristics since they both expose identical hexcell~containing collect~ing trays of 2.6 sq ft sampling area. Other pertinent instruments were one Gamma Time Intensity Recorder (TIR) and one to three Incremental Collectors (IC). The TIR, located at the platform center, detected and recorded gamm. radiation intensity versus time. The IC's sempled fallout incrementally with time to provide information regarding times of arrival and cessation, rates of arrival, and particle sizes. the windshield rin. Collecting surfaces of the instruments were level with On each platform, except for those of the YFNB 13 and YFNB 29 H (stern) ; relative wind velocities were documented with time by a recording anemometer (RA) which was located 10 ft above the after part of each platform. Wind speed data were adjusted, where necessary, to accommodate for this height difference from information extrapolated from Ref. 4. Wind directions were measured clockwise in degrees from the bow of the vessel except in the case of the HOW platform where they were measured from true north. Locatiomof instruments are also given by their angular displacement from the reference direction. The array of ground collectors consisted of 12 AOC, trays filled with environmental soil and buried flush with the ground. of all instruments are found in Ref. 3. Detailed descriptions PROBLEMS OF STANDARD PLATFORM WIND BIAS Collection bias is generally defined as the variation of collection with respect to some ideal value. In the case of the wind bias of the standard platform to fallout collection, there are two problems to consider: the vari- ation of collection within the platform (relative bias) and the relationship of some mean platform value to the ground value (ground bias). Fallout collection at Operation REDWING occurred under the influence of two wind systems and the present study is separated under these systems. They are designated as a single-wind (s.w.) system when a single relative wind velocity predominates or a multi-wind (m.w.) system when more than one wind velocity is involved.* *Due principally to ship maneuvers or "swing" of the anchored barges at the ' test site.