Let A be the albedo and p is the geometric albedo, then the phase integral is defined as
where is a unit of solid angle. If
The phase integral can be measured using Earth-based observations alone only for Mercury, Eric Weisstein's World of Astronomy Venus, Eric Weisstein's World of Astronomy and the Moon. Eric Weisstein's World of Astronomy
Albedo, Bond Albedo, Intensity, Phase Function
