The extraterrestrial solar beam illuminance on a plane perpendicular to a line between the centers of the Sun and Earth at the mean distance of the Earth from the Sun. Units: lm/m2. The currently accepted value is 133.1 kilolux (12,370 footcandles).
NOTE: This term and its definition were changed in RP-16-17 Addendum 2. Previously called solar illuminance constant.« Back to Definitions Index