Self-shading of upwelling irradiance for an instrument with sensors on a sidearm

The self-shading measurement error of the upwelling irradiance that is due to the presence of the instrument housing of an optical spectrometer with t he irradiance meter located on a sidearm was calculated with a Monte Carlo code. The dependence of the effect on the instrument dimensions, the values of real optical parameters, sea-surface roughness, and Sun zenith angle we re all studied to estimate maximum errors for two possible configurations o f a proposed new marine spectrophotometer. (C) 2000 Optical Society of Amer ica.