10313(  1) - 04/02/04 11:42  - [  1]

    PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS   ST ScI Use Only
                                                       ID:      10313
                                                       Version: 1
                                                       Check-in Date: 02-Apr-2004
                                                                      11:42:28

1.Proposal Title:
The Distribution and Variability of Io's SO2 Atmosphere
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2. Proposal For  3. Cycle  4. Parallel Pointing Tolerance
AR               13        <none>
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5. Investigators
                                                                                     Contact?
    PI: Ms. Lori M. Feaga                 Space Telescope Science Institute
   CoI: Dr. Melissa A. McGrath            Space Telescope Science Institute             N

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6. Abstract

We propose the first comprehensive analysis of archival HI Lyman-alpha images of Io
acquired in four HST programs from 1997-2001. This dataset comprises the best
currently available data to study some of the fundamental properties of Io's SO2
atmosphere, including spatial extent, surface pressure, origin (is the dominant
source sublimation or volcanos?), and variability. The two viable sources are both
expected to be highly variable, the sublimation due to the orders of magnitude
change in surface vapor pressure from day- to nightside, and the volcanos due to
their inherent variability. Indeed, a preliminary look at the archival dataset as a
whole confirms the presense of obvious variability for images of the same hemisphere
taken at different times (Feaga et al. 2003; see also Figure 4 of the proposal).
Only a single co-added exposure of the 34 Lyman-alpha images available has been
modeled previously (Strobel & Wolven 2001), so these data are ripe for a more
thorough analysis. Analysis tools for this type of HST data (STIS imaging
spectroscopy) have been developed previously by the PI for a project involving
atomic sulfur emission from Io (Feaga et al. 2002). This work is timely, focused,
and well within the scope of a one year, modestly-funded archival research program.
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                                                10313(  1) - 04/02/04 11:42  - [  2]

            Summary Form for Proposal  10313

  Item                         Used in this proposal
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  Proposal Category            AR
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