The Solar Cell Experiment of the first Brazilian satellite: 500 days of data analysis

The experiments conducted aboard satellites show the importance of the study of joint effects of thermal cycles, ionizing radiation damage, UV light and vacuum degradation on solar cells. The first satellite of the Brazilian Complete Space Mission, launched on February 9, 1993, hosts the Solar Cell Experiment (SCE). The objective of this experiment is to qualify in mission and real-time the space use silicon solar cells developed and manufactured in Brazil. The SCE is a small solar module composed by a single array of six silicon solar cells connected in series. The solar cells have the following characteristics: 2/spl times/2 cm/sup 2/ area, base resistivity of 10 ohm.cm and efficiency over 11% under AM0 condition. This module was laid down in an aluminum mechanical structure. The signal generated by the array is sent to a peak detector circuit located inside the mechanical structure. Three signals are available for the SCE behavior analysis: the peak detector output; the temperature sensor output, located inside the SCE mechanical structure under the solar array; and the attitude sensor signal, which gives the sunlight incidence angle with respect to the SCE plane. A computational method, which permits the recovering of the entire solar cell's I-V characteristics, was developed to the solar cells' parameter extraction using these three signals. During the first 500 days of the satellite operation, the SCE solar cells' degradation is smaller than expected.