Ultraviolet photometry from the Orbiting Astronomical Observatory. III. Observations of Venus, Mars, Jupiter, and Saturn longward of 2000 A

A number of high-quality spectra of Mars, Jupiter, the combined disk and rings of Saturn, as well as lower-quality spectra of Venus, have been obtained with an objective-grating spectrometer of the Wisconsin Experiment Package of GAO -2. An intercomparison of the Mars, Jupiter, and Saturn spectra has failed to disclose any discrete planetary absorptions. Continuous albedos have been derived for the four planets by using OAO-2 observations of G-type stars for X> 2700 A and a new photoelectric solar spectrum by A. L. Broadfoot for < 2700 A. The geometric albedo of Mars shows a steady increase below 3500 A which appears to be due to Rayleigh scattering combined with a decreasing surface reflectivity. The albedos of Venus, Jupiter, and Saturn show a maximum in reflectivity in the region of 2500 A.