What is a satellite solar array?
A satellite solar array is a collection of photovoltaic (PV) cells arranged on deployable panels that generate electrical power by converting sunlight into electricity. Solar arrays are the primary power source for virtually all Earth-orbiting satellites. They are typically deployed after launch (folded during launch to fit within the rocket fairing) and must provide power both during illuminated orbital phases and, combined with battery storage, through eclipse periods when the satellite passes through Earth's shadow.
Cell technology
Terrestrial solar panels typically use silicon cells with efficiency around 20–22%. Space solar cells use multi-junction III-V semiconductor cells (gallium arsenide / germanium substrate) with efficiencies of 29–32% in three-junction configurations and up to 35%+ for emerging four-junction and concentrator configurations. These higher efficiencies — despite much higher cost — are essential given the mass premium on every watt of power generated in space. The AM0 solar spectrum in space (1,366 W/m²) differs from the terrestrial AM1.5 spectrum, requiring cell optimisation for the space radiation environment.
Power budget and sizing
A GEO telecommunications satellite at 10–20 kW end-of-life power requires solar arrays of 60–100 m² total area. LEO constellations design for lower power: a Starlink Gen1 satellite uses approximately 1 kW with a single deployable solar panel of about 10 m². Degradation from space radiation reduces cell efficiency approximately 2–5% per year for LEO and 1–2% per year for GEO, so arrays must be sized to meet power requirements at end of life, meaning they are oversized at beginning of life. Battery systems (lithium-ion at 150–200 Wh/kg) store enough energy to sustain the satellite through eclipse periods (up to 70 minutes for LEO at certain periods of the year).