Extraterrestrial solar flux measurement limitations due to a Beer's law assumption and uncertainty in local time

The dependence on bandwidth of the error in estimating both optical depth and extraterrestrial solar flux due to an assumption of Beer's law applicability across finite bandwidths is determined by a numerical integration of Beer's law across the bandwidth. It was found that for 0.1% accuracy, 100-A bandwidths suffice for central wavelengths of 0.45 microm or greater; the maximum width yielding 0.1% accuracy decreases rapidly for shorter wavelengths. The accuracy to which solar elevation angle must be known to yield 0.1% accuracy is also examined and found to be a noteworthy though noncritical effect.