def build_b(self, scattering_fraction=<NUM_LIT>):
lg.info('<STR_LIT>' + str(scattering_fraction))<EOL>self.b = (self.b_b + self.b_water / <NUM_LIT>) / scattering_fraction<EOL>
Calculates the total scattering from back-scattering

        :param scattering_fraction: the fraction of back-scattering to total scattering default = 0.01833

        b = ( bb[sea water] + bb[p] ) /0.01833