A Space Power Subsystem Sizing program has been developed by the Aerospace Power Division of Wright Laboratory, Wright-Patterson Air Force Base, Ohio. Although a similar computational program has been developed in the Air Force, this program is integrated into a Quattro Pro spreadsheet.The Space Power Subsystem program (SPSS) contains the necessary equations and algorithms to calculate photovoltaic array power performance, including end-of-life (EOL) and beginning-of-life (BOL) specific power (W/kg) and areal power density (W/m2). These can then be displayed parametrically in graph form. Along the way equations are used to determine solar cell temperature effects, and cell performance degradation due to high energy particulate radiation as a function of altitude, orbital inclination, shield thickness and time in orbit.Additional equations and algorithms are included in the spreadsheet for determining maximum eclipse time as a function of orbital altitude, and inclination. The maximum eclipse time is used in sizing the secondary battery power subsystem and in determining this effect on solar array BOL and EOL power requirements. Altogether, approximately 45 equations and algorithms, and 50 variables are included in the sizing program.The advantage of integrating the sizing program with a Quattro Pro spreadsheet are numerous: Unlike a standard Fortran program, changes can be made with ease to the equations contained within the spreadsheet. New values for the variables can be input, and the results can be obtained and displayed on a single spreadsheet. Subsequently, parametric graphs can be immediately displayed and printed in hard copy or in viewgraph form.The Quattro Pro has been installed on a Northgate 386 computerThe Space Power Subsystem Sizing program (SPSS) has been used to determine the performance of several candidate power subsystems for both Air Force and SDIO potential applications. Trade-offs have been made between subsystem weight and areal power density (W/m2) as influenced by orbital high energy particle flux and time in orbit.