## ::Geometric albedo

### ::concepts

Albedo::phase Angle::surface Light::bodies Source::angles Albedo::small Category::ecliptic

In astronomy, the **geometric albedo** of a celestial body is the ratio of its actual brightness as seen from the light source (i.e at zero phase angle) to that of an *idealized* flat, fully reflecting, diffusively scattering (Lambertian) disk with the same cross-section. (Note that this phase angle refers to the direction of the light paths and is not a phase angle in its normal meaning in optics or electronics.)

Diffuse scattering implies that radiation is reflected isotropically with no memory of the location of the incident light source. Zero phase angle corresponds to looking along the direction of illumination. For Earth-bound observers this occurs when the body in question is at opposition and on the ecliptic.

The **visual geometric albedo** refers to the geometric albedo quantity when accounting for only electromagnetic radiation in the visible spectrum.

**Geometric albedo sections**

Intro Airless bodies Equivalent definitions Examples See also References

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