Solar panels on spacecraft

Photovoltaicsolar panels are the power source for almost all spacecraft ever launched. Modern spacecraft typically use multi-junction solar cell and gallium arsenide-based panels. The first solar-powered spacecraft was Vanguard 1, the second artificial satellite.

Near geocentric orbit, spacecraft extensively use solar panels. As well as almost all satellites, all crewed space stations have utilized solar panels; the International Space Station's array is the largest ever assembled in space, at 3,244 m and a 73 m wingspan. Solar power has been used other crewed spacecraft including Soyuz, Shenzhou, Crew Dragon, and Orion.

As distance from the Sun increased, solar radiation weakens, making radioisotope thermoelectric generators (RTGs) a more favorable power source for missions to Mars, to the outer planets, and those leaving the Solar System. Larger solar arrays have nonetheless been used extensively around Mars, and by the Jupiter missions of Juno, Jupiter Icy Moons Explorer, and Europa Clipper, partially due to a global shortage of plutonium-238. Other nuclear power alternatives in space include specialized fission reactors, such as aboard the SNAP-10A and US-A satellites, and NASA's modern Kilopower project.