9220(  1) - 12/20/00 23:46  - [  1]

    PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS   ST ScI Use Only
                                                       ID:      9220
                                                       Version: 1
                                                       Check-in Date: 20-Dec-2000
                                                                      23:39:48

1.Proposal Title:
The structure of Neptune's zonal  bands
------------------------------------------------------------------------------------
2. Proposal For  3. Cycle
AR               10
------------------------------------------------------------------------------------
4. Investigators
                                                                                     Contact?
    PI: Lawrence Sromovsky                University of Wisconsin-Madison

------------------------------------------------------------------------------------
5. Abstract

Neptune has zonal cloud bands with latitude boundaries and relative intensities that
vary substantially with wavelength and have evolved significantly between 1989
Voyager observations and the 1994-1998 period of HST observations. We propose to
investigate the nature of these cloud bands using 1996 archived WPFC2 and IRTF
NSFCAM observations, and 1998 WFPC2 and NICMOS archived observations. Latitude
dependent cloud particle composition and scattering properties will be constrained
by analysis of spectral variations and limb darkening characteristics. Zonal
averaging will permit high signal-to-noise ratios that are needed to characterize
relatively subtle features. We will explore effects of variations in cloud optical
depth, single-scattering albedo, cloud scale height, and possible variations in
methane mixing ratios, to evaluate possible causes for the banded appearance. This
effort will extend beyond previous Neptune-directed analyses of these data sets,
which focussed mainly on dynamics and the structure of discrete cloud features.
------------------------------------------------------------------------------------
                                                9220(  1) - 12/20/00 23:46  - [  2]

            Summary Form for Proposal  9220

  Item                         Used in this proposal
------------------------------------------------------------------------------------------------------------------------------------
  Proposal Category            AR
------------------------------------------------------------------------------------------------------------------------------------