A new analytical expression for the broadband transmission function co
rresponding to atmospheric Rayleigh scattering has been developed. Thi
s expression is based on the latest known spectral data on Rayleigh sc
attering as well as on the Neckel and Labs model, incorporating the mo
st recent corrections of the extraterrestrial solar spectrum. The prop
osed expression can be easily used by solar radiation models in order
to predict the beam, diffuse and global solar radiation.