Development of new shipborne aureolemeter to measure the intensities of direct and scattered solar radiation on rolling and pitching vessel

摘要

New shipborne aureolemeter was developed to improve the sun-tracking performance for accurate measurements of not only direct but also circumsolar radiation, even on a vessel weltering. Sun position is determined by a real-time image processing system with a CCD camera. The accuracy of the sun position determination is finer than 0.01°. The radiometer is tracked the sun under a feedback control with the derived sun position. For a sky radiance distribution measurement, the control target position on the CCD camera image is shifted a pixel corresponding to a measuring scattering angle. In the case of a scattering angle larger than 7°, the radiometer's tracking is conducted under feed forward control on the basis of the angle of roll and pitch monitored with a gyroscope. The instrument constants were determined from a Langley plot method. Test observation was conducted onboard the Antarctic research vessel (R/V) Shirase during the 56th Japanese Antarctic Research Expedition (JARE-56; 2014-2015). Aerosol optical thickness (AOT) was measured. The measurement of the sky radiance distribution is being analyzed to derive the aerosol optical properties.