Spacecraft are built so that the solar panels can be pivoted as the spacecraft moves. Thus, they can always stay in the direct path of the light rays no matter how the spacecraft is pointed. operating in the inner usually rely on the use of -managed to derive electricity from. Outside the orbit of, solar radiation is too weak to produce. Solar panels on spacecraft supply power for two main uses: • Power to run the sensors, active heating, cooling and telemetry.• Power for, sometimes called electric propulsion or solar-electric propulsion. Space contains varying levels of great electromagnetic radiation as well as. There are 4 sources of radiations: the (also called Van Allen belts), (GCR), and. The Van Allen belts and the. To date, solar power, other than for propulsion, has been practical for spacecraft operating no farther from the than the orbit of. For example,,,, and used solar power as does the Earth-orbiting, The first practical silicon-based solar cells were introduced by Russell Shoemaker Ohl, a researcher at in 1940. It was only 1% efficient. In April 25, 1954 in Murray Hill, New Jersey. They demonstrated their solar panel by using it to power a small toy. Solar panels need to have a lot of surface area that can be pointed towards the Sun as the spacecraft moves. More exposed surface area means more electricity can be converted from light energy from the Sun. Since spacecraft have to be small, this limits the amount of. Up until the early 1990s, solar arrays used in space primarily used solar cells. Since the early 1990s, -based solar cells became favored over silicon because they have a higher efficiency and degrade more slowly than silicon in the space. Each ISS solar array wing (often abbreviated "SAW") consists of two retractable "blankets" of solar cells with a mast between them. Each wing is the largest ever deployed in space, weighing over 2,400 pounds and using nearly 33,000 solar arrays, each measuring 8-cm square with 4,100 diodes. When fully extended, each is 35 metres (115 ft) in length and 12 metres (39 ft) wide. Each SAW is c.