Solar Array

Solar arrays are the primary power source for the vast majority of Earth-orbiting satellites. Multi-junction gallium arsenide (GaAs) cells achieve 30% efficiency — far higher than terrestrial silicon panels (20%). Arrays are typically deployed on articulated wings that rotate to track the Sun. During eclipse (when the satellite passes through Earth's shadow), onboard lithium-ion batteries provide power. Power budgets are tightly managed: the ISS has 2,500 m² of solar arrays generating 120 kW; a Starlink satellite generates 3 kW from a single compact array. Deep space missions beyond Jupiter often use radioisotope thermoelectric generators (RTGs) instead.