Help for PHO_MINNAERT

PURPOSE:

In this PDF, the user is asked for the only parameters needed for the 
Minnaerts's photometric function. This function needs just two input parameters 
(Albedo, geometric exponent k).

MATHEMATICAL BACKGROUND :

It is found empirically that Minnaert's law approximately describes the 
variation of brightness of many surfaces over a limited range of angles.
But the general law breaks down completely at the limb of a planet.

Minnaert (1941) suggested generalizing Lambert's law so that the power emitted 
per unit solid angle per unit area of the surface be proportional 
(cos(i)*cos(e))**k [ Lambert's power is proportional to (cos(i)*cos(e))**1 ].

bidirectional reflectance [1/str] :

r(i,e,g)=ALBEDO*(cos(i)*cos(e))**EXPONENT/cos(e)

REFERENCE :
M. Minnaert, The reciprocity principle in Lunar photometry,
Astrophysical Journal, Vol. 93, No. 2, p. 403-410, 1941
PROGRAMMER:

Friedel Oschuetz
Institute of Planetary Exploration
DLR
12484 Berlin (FRG)

PARAMETERS: