<Dl> <Dt> Spacecraft applications </Dt> </Dl> <Dl> <Dd> Solar panels on spacecraft are usually the sole source of power to run the sensors, active heating and cooling, and communications . A battery stores this energy for use when the solar panels are in shadow . In some, the power is also used for spacecraft propulsion--electric propulsion . Spacecraft were one of the earliest applications of photovoltaics, starting with the silicon solar cells used on the Vanguard 1 satellite, launched by the US in 1958 . Since then, solar power has been used on missions ranging from the MESSENGER probe to Mercury, to as far out in the solar system as the Juno probe to Jupiter . The largest solar power system flown in space is the electrical system of the International Space Station . To increase the power generated per kilogram, typical spacecraft solar panels use high - cost, high - efficiency, and close - packed rectangular multi-junction solar cells made of gallium arsenide (GaAs) and other semiconductor materials . </Dd> </Dl> <Dd> Solar panels on spacecraft are usually the sole source of power to run the sensors, active heating and cooling, and communications . A battery stores this energy for use when the solar panels are in shadow . In some, the power is also used for spacecraft propulsion--electric propulsion . Spacecraft were one of the earliest applications of photovoltaics, starting with the silicon solar cells used on the Vanguard 1 satellite, launched by the US in 1958 . Since then, solar power has been used on missions ranging from the MESSENGER probe to Mercury, to as far out in the solar system as the Juno probe to Jupiter . The largest solar power system flown in space is the electrical system of the International Space Station . To increase the power generated per kilogram, typical spacecraft solar panels use high - cost, high - efficiency, and close - packed rectangular multi-junction solar cells made of gallium arsenide (GaAs) and other semiconductor materials . </Dd> <Ul> <Li> <Dl> <Dt> Specialty Power Systems </Dt> </Dl> </Li> </Ul>

Where were photovoltaic cells first used to provide electricity