Solar panels on spacecraft
[1][obsolete source] The first practical silicon-based solar cells were introduced by Russell Shoemaker Ohl, a researcher at Bell Labs in 1940.
Bell had been interested in the idea as a system to provide power at remote telephone repeater stations, but the cost of the devices was far too high to be practical in this role.
The batteries were able to power the 20 MHz Mayak transmitter and Sergei Vernov's Scintillation counter, and these functioned for the entire lifetime of the satellite; until it reentered the Atmosphere nearly two years later.
[6][7][8] The success of the Vanguard system inspired Spectrolab, an optics company, to take up the development of solar cells specifically designed for space applications.
They had their first major design win on Pioneer 1 in 1958, and would later be the first cells to travel to the Moon, on the Apollo 11 mission's ALSEP package.
[10] 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.
Such spacecraft include the higher-power communications satellites (e.g., later-generation TDRS) and Venus Express, not high-powered but closer to the Sun.
[1] Sometimes, satellite operators purposefully orient the solar panels to "off point," or out of direct alignment from the Sun.
The degradation rate is a function of the differential flux spectrum and the total ionizing dose.
[14] To date, solar power, other than for propulsion, has been practical for spacecraft operating no farther from the Sun than the orbit of Jupiter.
Solar power for propulsion was also used on the European lunar mission SMART-1 with a Hall effect thruster.
[19][20] The InSight lander, Ingenuity helicopter, Tianwen-1 orbiter, and Zhurong rover all currently operating on Mars also utilize solar panels.
That comes to 120 kilowatts average system power, including 50% ISS time in Earth's shadow.
[23] For future missions, it is desirable to reduce solar array mass, and to increase the power generated per unit area.
Solar array mass could be reduced with thin-film photovoltaic cells, flexible blanket substrates, and composite support structures.
