In a recent paper [ 11, Theriault and Zeskind evaluate an approximate form for the bias encountered in conventional wavefront curvature ranging. We would like to point out that this result has been given previously by Hassab, Guimond, and Nardone [2].Theriault, and Zeskind note that reduction of this bias through increase in processing time exacerbates the problem; then they conclude that this bias represents a fundamental limitation on the performance of systems which employ the ranging equation.In [ 2 J , Hassab, Guimond, and Nardone present an approach that allows for removal of this limitation. It is demonstrated that the bias as well as the variance on the range estimates can be asymptotically reduced to negligible levels. The noisy time delays from a correlator output with short time average are mapped in a postprocessor onto the invariant source trajeo tory parameters over which smoothing is performed to reduce jointly the variance and the bias in the estimate of source range, course, and speed. This mapping imparts stationarity to the problem, thus allowing an effective increase in the averaging time of the localization systems beyond that permitted in a correlator.It is shown in [2] that theaddition of the proposed structure improves ,substantially on the techniques that process inappropriately mapped time delays or those that. transform directly the best time delays available into source motion estimates.