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.