Mission Design for the CubeSat OUFTI-1

CHAPTER 8Here we add an important hypothesis: the satellite turns on its orbit remaininginertially fixed. Considering that, as mentioned in the previous chapter, weare trying to avoid the attitude control, this is a big approximation as it’s almostimpossible that it’s not tumbling about its axis. Aware of this limitation, wealso recognize that we are performing a feasibility study and that all the resultsobtained are only indicative and will be useful to have an idea of the producedpower.Another possibility is to study the so-called barbecue mode: as the satellite isspinning around its axis and as all the faces are covered by solar cells, we couldidentify an equivalent surface to use for the calculation.We define each solar panel though its normal vector, its area and its efficiency.The area is the effective surface of solar cells and the efficiency is theEOL efficiency. This latter is defined as the maximum percent of incident powerconverted into electrical power:η = P maxC s SWhere C s is the solar constant and S the cell’s surface.(8.10)In particular, for this simulation we used a triple junction Gallium-Arsenidecell type having the properties reported in tables 8.1 and 8.2. We place twocells on each face.Table 8.1: Solar cells mechanical propertiesArea [cm 2 ] 30.18Weight [mg/cm 2 ] 86Thickness [µm] 150 ± 20Table 8.2: Solar cells electrical and thermal propertiesBOL 1E14 5E14 1E15η % 26.8 0.953 0.913 0.886Max Power Voltage V max [mV ] 2275 0.0953 0.920 0.908Max Power Current I max [mA/cm 2 ] 7.922 1 0.993 0.976dV max /dT [mV/ ◦ C] -6.4 -6.8 -6.8 -7.0dI max /dT [µA/cm 2 / ◦ C] 4.2 6.7 7.6 8.4absorbivity at 28 ◦ C α 0 0.91 1 1 1The values indicated in the last three columns are the coefficient to apply forthe fluence of electrons having 1 Mev energy indicated on top of the column inGalli Stefania 78 University of Liège