The Solar ConstantandSolar Incidences

The solar constant is the amount of solar radiation incidence that is received at a distance of 1 astronomical unit (AU) from the Sun. It is presently calculated as being 1,366 W/m2.

Due to the fact that the earth rotates around the sun and it's distance depends on the time of year, the actual direct solar incidence that Earth receives varies from 1,412 W/m2 in January to 1,321 W/m2 in July.

If you want to calculate specific solar incidences for a certain distance in AU's, use the following formula:

### Calculating Solar Incidences for the Solar System:

E = C • (1/Distance)2

Where

E: Incidence in W/m2.
C: Solar Constant at 1 AU (1,366 W/m2)
 EXAMPLE: What is the solar incidence at 1.5 AU? 1,366 • (1/1.5)2 = 607 W/m2

Below is a table of solar incidences for mission planning, whether for spacecraft thermal control to spacecraft power generation.

 Planets, Distances and Incidences Planet Mean Radius(AU) Solar Radiation Incidence(W/m2) Mercury 0.387 9,121 Venus 0.720 2,635 Earth/Moon 1.000 1,366 Mars 1.520 591 Asteroid Belt 2.500 219 3.5 AU Distance 3.500 112 Jupiter 5.190 51 7 AU Distance 7.000 28 Saturn 9.510 15 Uranus 19.000 4 Neptune 30.000 1.5 Pluto 39.480 0.9