A new instrument for measurement of the solar aureole radiance distribution from unstable platforms

Abstract

A novel imaging solar aureole radiometer, which can obtain absolute radiometric measurements of the solar aureole when operated on an unstable platform, is described. A CCD array is used to image the aureole, while a neutral density occulter on a long pole blocks the direct solar radiation. This ensures accurate direction registration as the sun appears in acquired images, and the total circumsolar region is measured simultaneously. The imaging nature of this instrument along with a special triggering device permit acquisition of the circumsolar sky radiance within 7.5°of the center of the solar disk, and within 1°of the edge of the solar disk. This innovation makes possible, for the first time, reliable and accurate radiometric measurements of the solar aureole from unstable mobile platforms such as ships. This allows determination of the small angle atmospheric light scattering. The instrument has been used in field studies of atmospheric aerosols and will be used in satellite validation and calibration campaigns.