Photometric variability of Uranus, 1972-1996

We present b (472 nm) and v (551 mm) lightcurves for Uranus based on photoelectric photometry obtained at every apparition from 1972 to 1996. The two branches of the lightcurve before and after the 1985 solstice are offset by similar to 0.01 mag in b and similar to 0.02 mag in y. indicating that the disk-integrated albedo of Uranus increased slightly after solstice. The solar phase coefficients of Uranus also increased at about the same time. The b lightcurve is consistent with the 1986 Voyager 2 BL (477 nn) I/F latitudinal scans. The y lightcurve differs significantly from the GR (572 nn) scan, suggesting that the polar region may have brightened somewhat over the past 25 years. (C) 1999 Academic Press.