“…Since this determination of system performance involves predicting the future statistically (and such predictions are subject to errors and unknowns), it is necessary (for a proper statistical description) to define system performance in terms of three independent component parts. These parts are termed grade of service, time availability, and service probability [Barsis et al, 1961;Spaulding, 1982, and references therein]. We will, of course, relate these system performance "parts" to IONCAP, VOA-CAP, and HFMUFES, and more modern statistical terminology.…”