ARTICLE NO. IS985901 Stellar Occultation Observations of Saturn’s North-Polar Temperature Structure

thermal gradients are due to a combination of diffractive scintil-lations and horizontal temperature variations. Given that iso-We have observed a stellar occultation of GSC5249-01240 thermal model fits and numerical inversions cannot separateby Saturn’s north polar region on November 20, 1995 from individual contributions to observed temperature gradients,NASA’s Infrared Telescope Facility (IRTF). This is the first such as from vertical variations, horizontal variations, and scin-recorded occultation by the polar region of a giant planet. The tillations, this occultation requires further study. 1998 Aca-occulted region extends 88 km in vertical height and 660 km demic Pressin horizontal length, over a region from 82.58 to 858 in planeto-Key Words: atmosphere dynamics; atmosphere structure; oc-centric latitude and from 208 to 308 in planetocentric longitude. cultations; Saturn atmosphere.Based on isothermal model fits to the light curve, we find an equivalent isothermal temperature of 130 6 10 K at a pressure level of 1.6 6 0.1 mbar, which corresponds to a half-light lati-I. INTRODUCTIONtude of 83.2 6 0.28 and longitude of 24.1 6 0.58. Using numeri-cal inversion procedures, we have retrieved the temperature Most of our knowledge of Saturn’s vertical temperatureprofile of the occulted region, which suggests an increase in structure has come from (i) a series of radio (RSS) occulta-temperature (with radius) of 14.5 K between 6 and 10 mbar