DPS 34th Meeting, October 2002
Session 13. Outer Planets: Atmospheric Dynamics, Clouds
Oral, Chair(s): G.S. Orton and K.A. Rages, Tuesday, October 8, 2002, 1:30-3:30pm, Room M

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[13.11] HST Observations of Neptune in 2002

L. A. Sromovsky, P. M. Fry (Univ. of Wisconsin), K. H. Baines (JPL), S. S. Limaye (Univ. of Wisconsin)

New HST WFPC2 observations providing complete longitudinal coverage of Neptune are scheduled for 9 August 2002, 4 years after the last comparable observations in August 1998. By 1996, the 1989 Great Dark Spot and its bright companion cloud had long since disappeared, and by 1998 the more recent Northern Great Dark Spot discovered at 32\deg N in 1994 (Hammel and Lockwood 1997, Science \bf 268, 1740-42) had also disappeared as a dark feature, although the continued presence of its underlying vortex was indicated by the apparent persistence of its prominent pole-ward bright companion cloud (Sromovsky et al. 2002b, Icarus \bf 156, 16-36). The companion-free dark spot, discovered at 16\deg N in 1996 (Sromovsky et al. 2001 Icarus \bf 149, 459-488)), had also disappeared by 1998. Between 1996 and 1998 there was an increase in the coverage of bright cloud features and an overall increase in disk-integrated albedo of 1.4±1.4%, 1.9±1% , and 9.5±1% for F467M, F673N, and F850LP HST filters respectively (Sromovsky et al. 2002a, Icarus \bf 150, 244-260)). These increases are part of a much longer trend extending from 1980 to 2000, during which Neptune brightened 11% in the b band (472 nm) and 10% in the y band (551 nm) (Lockwood and Thompson (2002, Icarus \bf 156, 37-51). The new HST observations will enable us to determine if the brightening of Neptune has continued, if there have been changes in the distribution of bright cloud features or cloud bands, if new dark spots or bands have formed, if wind speeds have changed, and new estimates of Neptune's vertical cloud structure.

Based on observations made with the NASA/ESA Hubble Space Telescope. STScI is operated by the Association of Universities for Research in Astronomy, Inc., under NASA Contract NAS 5-26555.

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Bulletin of the American Astronomical Society, 34, #3< br> © 2002. The American Astronomical Soceity.