Observations have been performed with the IUE of the H Ly &agr; emission brightness of Jupiter to measure the center to limb variation due to radiative transfer effects alone. The effects of spatial variations in the atmosphere have been removed by observing fixed locations in Jupiter's atmosphere as the planet rotated (assuming that any thermospheric winds are less than roughly 500 m/sec). The observed center to limb curves are both bright and optically thin in appearance, leading to a difficulty in the interpretation in terms of resonant scattering. Model runs reveal that the observed curves are consistent with resonant scattering for the expected H abundance, but these models are not consistent with the observed high brightness. Modeling the high brightness by resonant scattering alone is possible, but the model then no longer fits the observed center to limb curve. We interpret these results to support a large contribution to the observed emission from resonant scattering of solar emission, plus an additional optically thin emission process which also requires the solar input. ¿ American Geophysical Union 1990