“…The energy beyond this diameter (i.e., the spillage for a circular target) would be mathematically equal to the relative intensity at the defi ned radius, assuming the Gaussian is a reasonable approximation to the solar aureole. A better fi t to the true sunshape can be accomplished by adding to the second moment (sigma 2 ) higher moment terms such as fourth moment (a measure of kurtosis), sixth moment, etc., in a Hermitian series (Walzel et al, 1977), but if beam errors are comparable to the second moment of the sunshape the improvement is marginal and the complication signifi cant. For detailed fl ux analysis, it is useful to include terms in the Hermite series to sixth order.…”