A new procedure is presented for determining <i>in situ</i> the solar calibration constant, i.e., the Sun-sky radiometer counts for a direct normal solar flux extrapolated to the top of the atmosphere. The method makes use of a modified version of the Langley plot based on the use of an inversion code of column-integrated aerosol size distribution, and it is ordinarily applied to calibrate Prede Sun-sky radiometers. To analyze how such an <i>in situ</i> method can work accurately, the technique has been applied to a five-month dataset obtained from measurements taken in Rome, Italy, by a Prede Sun-sky radiometer from 22 April to 5 November 2001. The precision of the <i>in situ</i> method has been estimated to within 1–2.5%, depending on the wavelength.
© 2004 Optical Society of America
Monica Campanelli, Teruyuki Nakajima, and Bruno Olivieri, "Determination of the Solar Calibration Constant for a Sun-Sky Radiometer: Proposal of an In-Situ Procedure," Appl. Opt. 43, 651-659 (2004)