Help for PHOTFIT2_BURATTI3

PURPOSE:

In this PDF, the user is asked for the parameters and there limits needed to 
fit Buratti's photometric function.

MATHEMATICAL BACKGROUND :

bidirectional reflectance [1/str] :

r(i,e,g) = A * cos(i)/(cos(i)+cos(e)) * burf + (1 - A) * cos(i)

burf = ((1 - A) * 2/3 + A*E)*phi - (1 - A) * 2/3 * ((sin(phase) + (PI - phase) 
* cos(phase))/PI)

BURATTI3 approximation : 
phi=1.0 + params[1] * phase + params[2] * (exp(-params[3] * phase) - 1.0)


REFERENCE :
Bonnie Buratti, Voyager Disk Resolved Photometry of the Saturnian Satellites,
	Icarus, Vol. 59, p. 392-405, 
Bonnie Buratti, Joseph Veverka, Voyager Photometry of Europa,
	Icarus, Vol. 55, p. 93-110, 1983

PROGRAMMER:

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

PARAMETERS: