8760( 1) - 12/30/99 13:05 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 8760 Version: 1 Check-in Date: 30-Dec-1999 12:32:42 1.Proposal Title: The Dynamics of Dark Spots on Neptune ------------------------------------------------------------------------------------ 2. Proposal For 3. Cycle AR 9 ------------------------------------------------------------------------------------ 4. Investigators Contact? PI: Lawrence Sromovsky University of Wisconsin-Madison ------------------------------------------------------------------------------------ 5. Abstract HST and groundbased observations of Neptune since 1991 provide potentially strong constraints on the behavior of Neptune's Northern Great Dark Spot (NGDS), first discovered in October 1994 HST images (Hammel et al., Science 268, 1995). Unlike the 1989 Great Dark Spot revealed by Voyager, which moved continuously equatorward and dissipated unseen during 1990, the NGDS seems to have remained at ~ 35degrees N from 1994 through at least 1996, suggesting that its zonal drift rate may be relatively constant and that its position may be highly predictable. An empirical model of its motion can be constrained by analysis of HST archive images in combination with existing groundbased images that are sensitive to the bright companion clouds of the NGDS. By combining sporadic groundbased observations of the companion clouds during 1993, 1994, 1996, 1997, and 1998, with HST observations of both the NGDS and its bright companion in 1994, 1995, and 1996, and HST observations of only bright companions in 1991, 1997, and 1998, we propose to determine spectral and other signatures for the companion clouds, the evolution of their characteristics, and whether or not the NGDS is a single circulation feature that has been present during this entire period. We expect to provide new constraints on NGDS dynamics and companion lifetimes and a prediction equation for NGDS future positions. ------------------------------------------------------------------------------------ 8760( 1) - 12/30/99 13:05 - [ 2] Summary Form for Proposal 8760 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category AR ------------------------------------------------------------------------------------------------------------------------------------