Power-Supply Systems and Test Solar Cells

Conversion of solar energy with photovoltaic solar cells was decided to be the most practical means of meeting the low-level power requirements throughout the desired 1-year lifetime of the satellite. Rechargeable batteries were necessary to supply all power required during the orbital dark periods, as well as to supply a large part of the power required during interrogations in sunlight. Two separate solar power supplies were installed, one for each telemeter. Each supply was required to furnish 10 milliamperes of standby current and 110 milliamperes during interrogations at 12 volts nominal. The power supplies were designed for 1-minute interrogations during each orbit; orbital periods were approximately 100 minutes and orbital dark times varied from Oto 35 percent of each orbital period. In addition, the satellite was to be spin stabilized at 200 rpm at launch, but was expected to tumble at approximately 20 rpm after several weeks. In addition to the solar cells used for power, five groups of solar cells were mounted on the forward shell to obtain data on the relative effectiveness of protective covers for the cells.