normal solar illuminance
illuminance produced by direct sunlight on a surface on the Earth that is perpendicular to the direction of illumination by the Sun
Note 1 to entry: Normal solar illuminance is not the same as direct solar illuminance, which is measured on a horizontal surface on the Earth, not necessarily perpendicular to the direction of illumination by the Sun.
Note 2 to entry: The normal solar illuminance is expressed in lux (lx = lm⋅m−2).
Note 3 to entry: This entry was numbered 17-825 in CIE S 017:2011.