TIMED-H, an ideal application for GaAs/Ge solar cells

The TIMED Mission required spacecraft designs that included radiation resistance and minimization of orbital drag. A high efficiency, radiation resistant, body-mounted solar cell array would help meet these requirements, although body-mounting causes the array temperature to run high. These critical features of radiation resistance, high efficiency and low temperature sensitivity are precisely those characteristics for which gallium arsenide (GaAs/Ge) cells are noted. Comparison with silicon (Si) cell technology for the TIMED-H Observatory solar array showed that the combined effects result in an end of life power density for GaAs/Ge more than 1.5 times that of Si, a frontal (drag) area less than 2/3 that for Si, a mass less than 3/4 that for Si and an end of life cost only 1.16 times that for Si. These considerations led to the selection of GaAs/Ge cells for both the TIMED-H and -L baseline array designs