SystemXsecBscatterSphere
returns Backscatter cross-sectional
area of a sphere using the Rayleigh approximation
From Rinehart (1997), Eqn 4.9 and 5.7
SystemXsecBscatterSphere(D, lam, K=0.93)
R. E. Rinehart, 1997 Radar for Meteorologists Rinehart Publishing