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18 May 2012 Long-term measurements of atmospheric point-spread functions over littoral waters as determined by atmospheric turbulence
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During the FATMOSE trial, held over the False Bay (South Africa) from November 2009 until October 2010, day and night (24/7) high resolution images were collected of point sources at a range of 15.7 km. Simultaneously, data were collected on atmospheric parameters, as relevant for the turbulence conditions: air- and sea temperature, windspeed, relative humidity and the structure parameter for refractive index: Cn 2. The data provide statistical information on the mean value and the variance of the atmospheric point spread function and the associated modulation transfer function during series of consecutive frames. This information allows the prediction of the range performance for a given sensor, target and atmospheric condition, which is of great importance for the user of optical sensors in related operational areas and for the developers of image processing algorithms. In addition the occurrence of "lucky shots" in series of frames is investigated: occasional frames with locally small blur spots. The simultaneously measured short exposure blur and the beam wander are compared with simultaneously collected scintillation data along the same path and the Cn 2 data from a locally installed scintillometer. By using two vertically separated sources, the correlation is determined between the beam wander in their images, providing information on the spatial extension of the atmospheric turbulence (eddy size). Examples are shown of the appearance of the blur spot, including skewness and astigmatism effects, which manifest themselves in the third moment of the spot and its distortion. An example is given of an experiment for determining the range performance for a given camera and a bar target on an outgoing boat in the False Bay.
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Arie N. de Jong, Piet B. W. Schwering, Koen W. Benoist, Willem H. Gunter, George Vrahimis, and Faith J. October "Long-term measurements of atmospheric point-spread functions over littoral waters as determined by atmospheric turbulence", Proc. SPIE 8355, Infrared Imaging Systems: Design, Analysis, Modeling, and Testing XXIII, 83550M (18 May 2012);

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