In 1992 the Far-Ultraviolet Space Telescope ( FAUST ) provided measurements of the ultraviolet ( 140-180nm ) diffuse sky background at high , medium , and low Galactic latitudes .
A significant fraction of the detected radiation was found to be of Galactic origin , resulting from scattering by dust in the diffuse interstellar medium .
To simulate the radiative transfer in the Galaxy , we employed a Monte Carlo model which utilized a realistic , non-isotropic radiation field based on the measured fluxes ( at 156nm ) and positions of 58,000 TD-1 stars , and a cloud structure for the interstellar medium .
The comparison of the model predictions with the observations led to a separation of the Galactic scattered radiation from an approximately constant background , attributed to airglow and extragalactic radiation , and to a well constrained determination of the dust scattering properties .
The derived dust albedo a~ { } = ~ { } 0.45 ~ { } \pm~ { } 0.05 is substantially lower than albedos derived for dust in dense reflection nebulae and star-forming regions , while the phase function asymmetry g~ { } = ~ { } 0.68 ~ { } \pm~ { } 0.10 is indicative of a strongly forward directed phase function .
We show the highly non-isotropic phase function to be responsible , in conjunction with the non-isotropic UV radiation field , for the wide range of observed correlations between the diffusely scattered Galactic radiation and the column densities of neutral atomic hydrogen .
The low dust albedo is attributed to a size distribution of grains in the diffuse medium with average sizes smaller than those in dense reflection nebulae .