ICARUS 73, 349-378 (1988) Uranian Ring Orbits from Earth-Based and Voyager Occultation Observations RICHARD G. FRENCH, *,’ J. L. ELLIOT,**t LINDA M. FRENCH,*,* JULIE A. KANGAS,V KAREN J. MEECH,* AND MICHAEL E. RESSLERt33 *Department of Earth, Atmospheric, and Planetary Sciences, and tDepartment of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 MARC W. BUIE Institute for Astronomy, 2680 Woodlawn Drive, Honolulu, Hawaii 96822 JAY A. FROGEL Kitt Peak National Observatory, National Optical Astronomy Observatory, 950 North Cherry Avenue, Tucson, Arizona 85726 J. B. HOLBERG Lunar and Planetary Laboratory, University of Arizona, Tucson, Arizona 85713 JESUS J. FUENSALIDA Znstituto de AstroJsica de Canarias, Universidad de la Laguna, S.IC. de Tenerife, Islas Canarias, Spain AND MARSHALL JOY Department of Astronomy, University of Texas-Austin, R. L. Moore Hall, Austin, Texas 78712 Received May 22, 1987; revised August I I, 1987 zyxwvutsrqponmlkjihgfedcbaZYXWV A new kinematical model for the Uranian rings has been determined from a combination of previously analyzed Earth-based stellar occultation data, three new stellar occultation data sets obtained in 1985 and 1987, and Voyager 2 occultation results. The new Earth-based occultations were of stars U23, U25, and U28 from the prediction list of Mink and Klemola (D. J. Mink and A. Klemola, 1985, Asfron. J. 90, 1894-1899). The 4 May 1985 U23 occultation was observed from Cerro Tololo Interamerican Observatory (CTIO), McDonald Observatory, and Teide Observatory on Tenerife, and the 24 May 1985 U25 event was observed from CTIO, McDonald Observatory, and the IRTF on Mauna Kea. The 26 April 1987 U28 occultation was observed from the IRTF. Square-well models were fitted to the observed ring profiles to determine ring midtimes, widths, and optical depths. Voyager photopolarhn- eter and ultraviolet spectrometer observations of the cr Sgr and p Per stellar occultations provided strong constraints on the direction of the planetary pole 'Now at Department of Astronomy, Wellesley Col- ’ Now at Department of Physics and Astronomy, lege, Wellesley, MA 02181. University of Hawaii, Honolulu, HI 96822. 2 Guest Observer, Cerro To1010 Interamerican Ob- servatory, La Serena, Chile. 349 0019-1035/88 $3.00 Copyright 0 1988 by Academic Press. Inc. All rights of reproduction in any form reserved.