An automatic haze recorder.
Merrill, Bushnell Darby
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This report is primarily concerned with a detailed description of an automatic haze recorder. An introductory haze discussion is included to facilitate the overall evaluation of the program. Although there is a wealth of experimental data for ground-to-ground haze measurements. there exist only fragmentary data for the air-to-ground case. The data of Waldram, and Carman and Carruthers comprise the known extent of published aerial haze studies which are statistically based on a series of programmed flight-test measurements. Even in these cases the number of flights was small. It is therefore essential to the formation of a statistical model of the atmosphere that extensive flight measurements be made over various conditions and up to altitudes of 40000 ft. The automatic haze recorder consists basically of an airborne telephotometer and its associated equipment: the telephotometer itself, an indexing mount~ a recording assembly, and a control assembly and starting box. Each of these items is described in detail. The base of the telephotometer consists of a device which rotates a right prism about an axis normal and concentric to one of its faces. The telephotometer is mounted on the floor of an aircraft in such a manner that this prism assembly extends below the bottom skin of the aircraft, and that the axis of the prism rotation is maintained parallel to the surface of the earth. The upwelling light from a 15° cone entering the prism is reflected along its axis of rotation and, by means of a fixed right prism into the photometric system. In this manner the rotating prism scans a path 15° wide, which stretches beneath the aircraft from horizon to horizon. In the photometric system the upwelling light is projected through an appropriate filter onto a photomultiplier tube. The output of this tube is read directly as the vertical deflection of an oscilloscope which is mounted in the recording assembly. The horizontal deflection of this scope is made proportional to the scanning angle by a gear-driven potentiometer. In this manner the scope makes a trace of upwelling intensity vs angle for a given set of conditions. Each scope trace, together with other pertinent data, is photographed by the recording assembly. The indexing mount rotates the telephotometer, and thus the scanning plane, about the vertical axis. The control assembly, once started, automatically cycles the overall system in the following manner. A blue record, then a green record, then a red record are separately photographed at the indexing mount setting (azimuth) of 0°. Then the mount turns the instrument to an azimuth of 45° and the above three records are made again. This sequence is repeated at settings of 90°, 135°, 180°, 135°, 90°, and 45°. The head is then returned to 0°, and the assembly is again ready for another cycle. The lapsed time of the complete cycle is somewhat less than 1/3 of a minute. The instrument has been constructed and successfully laboratory-tested. It has had only a single, preliminary flight test, but on this the performance equaled or exceeded the design expectations. Proposals for future flight-test programs are discussed.
Thesis (M.A.)--Boston University
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