We describe a rapid inversion algorithm for constructing synthetic terrestrial spectra from measurements made by instruments with multiple narrowband detectors. We show tests of algorithm performance over large dynamic ranges of ozone amount, solar zenith angle, surface albedo, and optical depths of aerosol and clouds. These tests demonstrate that the accuracy of synthetic spectra for total, diffuse, and direct irradiances will be limited by instrument accuracy in almost all cases. Consequently, we show uncertainty analyses for the effects of measurement and calibration errors (including filter wavelength shifts), and the impact of filter wavelength selection on the inverted spectra. ¿ 1998 American Geophysical Union