Help for PHO_VEVERKA

PURPOSE:

In this PDF, the user is asked for the only parameters needed for the Veverka's
photometric function.

MATHEMATICAL BACKGROUND :

Exept close to zero phase, this expression is a good description of light 
scattered by low-albedo bodies of the solar system, such as the Moon and 
Mercury, for which only light that has been scattered once contributes 
significantly to the brightnes.

bidirectional reflectance [1/str] :

r(i,e,g) = ( cos(i) / (cos(e)+cos(e)) ) 
	 * exp(-DVEVERKA * phase) 
	 * (A_VEVERKA + B_VEVERKA * phase + C_VEVERKA)

usually :
C_VEVERKA=1-A_VEVERKA


REFERENCE :
Joseph Veverka, J. Goguen, S. Young, J. Elliont, Scattering of light from 
particulate surfaces. 
I. A laboratory assessment of multiple-scattering effects.
Icarus, Vol. 34, p. 406-414


PROGRAMMER:

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

PARAMETERS: