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Imke de Pater, H. Roe (UC Berkeley), B. Macintosh, S. Gibbard, C. Max, D. Gavel (IGPP/LLNL)
We observed Uranus with the recently commissioned AO/NIRSPEC system (Adaptive Optics system with the Near-Infrared echelle Spectrograph) on the 10-m W.M. Keck telescope, UT June 17 and 18, 2000. NIRSPEC allows one to take images and spectra simultaneously. Here we will discuss the images at wavelengths between 1 and 2.4 micron. Due to the location of the rings' pericenter, the rings were much brighter in the north than the south, which resulted in excellent ring images. Inside of the \epsilon ring at least three more (individually slightly resolved) rings are visible: from the outside inwards these are: 1) combined \delta,\gamma,\eta rings, 2) combined \beta,\alpha rings, and 3) combined 4,5,6 rings.
On the planet itself we detected at least 8 different cloud features, five of which were in the northern hemisphere. Two features could be tracked over a 40-60 degree longitude range, and yield wind velocities of 175 ± 35 m/s at a latitude of +30\circ, and of 120 ± 40 m/s at +40\circ latitude. The highest latitude reached by HST NICMOS was +27\circ, where a velocity of 20 m/s was measured (Karkoschka, 1998). Has the wind speed changed? Or is there a very steep gradient in the profile? Our data suggest the wind profile to be similar to that derived for Neptune, though at reduced velocities.
This research was supported in part by the STC Program of the National Science Foundation under Agreement No. AST-9876783, and in part under the auspices of the US Department of Energy at Lawrence Livermore National Laboratory, Univ. of Calif. under contract No. W-7405-Eng-48.