Proposal_Information Title: Composition of Surface Units on Io Proposal_Category: GO Scientific_Category: Solar System Cycle: 5 Investigators PI_name: John Spencer PI_Institution: Lowell Observatory CoI_Name: Melissa McGrath CoI_Institution: Space Telescope Science Institute Contact: Y ! Y or N (designate at most one contact) CoI_Name: Alfred McEwen CoI_Institution: USGS Flagstaff CoI_Name: Paola Sartoretti CoI_Institution: Space Telescope Science Insititute CoI_Name: John Clarke CoI_Institution: University of Michigan CoI_Name: John Trauger CoI_Institution: Jet Propulsion Laboratory CoI_Name: Gilda Ballester CoI_Institution: University of Michigan Abstract: ! Free format text (please update) Io's surface composition is still poorly understood: SO_2 is the only definitively identified component. We plan to obtain a global multispectral map of Io in 12 mostly narrowband filters from 0.22 to 0.79 microns, to obtain the most detailed picture yet of the composition and spatial distribution of its many surface units. The many wavelengths will allow much better determination of unit spectra than previous broadband imaging, which should lead to more definitive compositional identifications. We are particularly interested in the composition of the polar regions, and the spectrally unusual deposits of the Pele volcano, first noted in our Cycle 4 HST images of Io, which may be rich in S_2O or Na_2S. Questions ! Free format text (please update) Observing_Description: We will image four longitudes on Io (c. 70, 160, 250, and 340 degrees), giving complete surface coverage, in twelve filters, at 0.218, 0.255, 0.343, 0.374, 0.409, 0.467, 0.501, 0.548, 0.589, 0.659, and 0.779 microns (an exception is that we will only use the 0.218 and 0.255 micron filters at 160 and 340 degrees longitude). Exposure times range from 1000 seconds (F343N) to 0.3 seconds (F791W): we have determined them from exposures used successfully for Cycle 4 Io observations with WFPC, scaled for the relative sensitivity of the filters (from the WFPC2 Handbook) and the wavelength dependence of the flux from Io. Like the Cycle 4 images, these exposures will yield about 30,000 electrons per pixel on Io, giving a S/N of 170, more than adequate for distinguishing candidate materials on Io. S/N in the 0.218 micron filter will be lower, as we will be restricted to 500 second integrations to keep within our orbit limit, but 1000- second images taken in Cycle 4 by Clarke et al. have adequate S/N and ours will only be lower by sqrt2. We can image each Io longitude through all these filters in two HST orbits. Real_Time_Justification: The observations are time-critical in that we require Io to be within +/- 15 degrees of the requested orbital longitude in order to obtain global coverage. As described in the justification, we will take CCD spectra of Io from the Lowell Observatory 72'' telescope at the same orbital and solar phases as the HST observations, for spectrophotometric calibration. Calibration_Justification: ! Move appropriate text from Real_Time_Justification Additional_Comments: Solar_System_Targets Target_Number: 1 Target_Name: IO-LON70 Description: SATELLITE IO Level_1: STD=JUPITER Level_2: STD=IO Window: OLG OF IO BETWEEN 60 80 RANGE EARTH JUPITER LT 4.7 SEP OF JUPITER IO FROM EARTH GT 5.0" Flux: SURF(V)=5.14 B-V = 1.2 Comments: Io should less than 4.7 AU from Earth for maximum resolution, and more than 5 arcsec from Jupiter's limb to avoid Jupiter scattered light Target_Number: 2 Target_Name: IO-LON160 Description: SATELLITE IO Level_1: STD=JUPITER Level_2: STD=IO Window: OLG OF IO BETWEEN 140 180 RANGE EARTH JUPITER LT 4.7 SEP OF JUPITER IO FROM EARTH GT 5.0" Flux: SURF(V)=5.14 B-V = 1.2 Comments: Io should less than 4.7 AU from Earth for maximum resolution, and more than 5 arcsec from Jupiter's limb to avoid Jupiter scattered light Target_Number: 3 Target_Name: IO-LON250 Description: SATELLITE IO Level_1: STD=JUPITER Level_2: STD=IO Window: OLG OF IO BETWEEN 235 265 RANGE EARTH JUPITER LT 4.7 SEP OF JUPITER IO FROM EARTH GT 5.0" Flux: SURF(V)=5.14 B-V = 1.2 Comments: Io should less than 4.7 AU from Earth for maximum resolution, and more than 5 arcsec from Jupiter's limb to avoid Jupiter scattered light Target_Number: 4 Target_Name: IO-LON340 Description: SATELLITE IO Level_1: STD=JUPITER Level_2: STD=IO Window: OLG OF IO BETWEEN 325 355 RANGE EARTH JUPITER LT 4.7 SEP OF JUPITER IO FROM EARTH GT 5.0" Flux: SURF(V)=5.14 B-V = 1.2 Comments: Io should be in full sunlight (not in Jupiter's shadow umbra or penumbra) for all exposures. Io should less than 4.7 AU from Earth for maximum resolution, and more than 5 arcsec from Jupiter's limb to avoid Jupiter scattered light Visits Visit_Number: 1 Exposure_Number: 1 Target_Name: IO-LON70 Config: WFPC2 Opmode: IMAGE Aperture: PC1 Sp_Element: F343N Optional_Parameters: CR-SPLIT=DEF ATD-GAIN=15 Number_of_Iterations: 1 Time_Per_Exposure: 1200S Exposure_Number: 2 Target_Name: IO-LON70 Config: WFPC2 Opmode: IMAGE Aperture: PC1 Sp_Element: F390N Optional_Parameters: ATD-GAIN=15 Number_of_Iterations: 1 Time_Per_Exposure: 70S Exposure_Number: 3 Target_Name: IO-LON70 Config: WFPC2 Opmode: IMAGE Aperture: PC1 Sp_Element: F410M Optional_Parameters: ATD-GAIN=15 Number_of_Iterations: 1 Time_Per_Exposure: 10S Exposure_Number: 4 Target_Name: IO-LON70 Config: WFPC2 Opmode: IMAGE Aperture: PC1 Sp_Element: F467M Optional_Parameters: ATD-GAIN=15 Number_of_Iterations: 1 Time_Per_Exposure: 3.0S Exposure_Number: 5 Target_Name: IO-LON70 Config: WFPC2 Opmode: IMAGE Aperture: PC1 Sp_Element: F791W Optional_Parameters: ATD-GAIN=15 Number_of_Iterations: 1 Time_Per_Exposure: 0.23S Exposure_Number: 6 Target_Name: IO-LON70 Config: WFPC2 Opmode: IMAGE Aperture: PC1 Sp_Element: F375N Optional_Parameters: ATD-GAIN=15 Number_of_Iterations: 1 Time_Per_Exposure: 500S Exposure_Number: 7 Target_Name: IO-LON70 Config: WFPC2 Opmode: IMAGE Aperture: PC1 Sp_Element: F502N Optional_Parameters: ATD-GAIN=15 Number_of_Iterations: 1 Time_Per_Exposure: 16S Exposure_Number: 8 Target_Name: IO-LON70 Config: WFPC2 Opmode: IMAGE Aperture: PC1 Sp_Element: F547M Optional_Parameters: ATD-GAIN=15 Number_of_Iterations: 1 Time_Per_Exposure: 0.4S Exposure_Number: 9 Target_Name: IO-LON70 Config: WFPC2 Opmode: IMAGE Aperture: PC1 Sp_Element: F588N Optional_Parameters: ATD-GAIN=15 Number_of_Iterations: 1 Time_Per_Exposure: 3.0S Exposure_Number: 10 Target_Name: IO-LON70 Config: WFPC2 Opmode: IMAGE Aperture: PC1 Sp_Element: F658N Optional_Parameters: ATD-GAIN=15 Number_of_Iterations: 1 Time_Per_Exposure: 6.0S Exposure_Number: 11 Target_Name: IO-LON70 Config: WFPC2 Opmode: IMAGE Aperture: PC1 Sp_Element: F255W Number_of_Iterations: 1 Time_Per_Exposure: 600S Visit_Number: 2 Exposure_Number: 1 Target_Name: IO-LON160 Config: WFPC2 Opmode: IMAGE Aperture: PC1 Sp_Element: F343N Optional_Parameters: CR-SPLIT=DEF ATD-GAIN=15 Number_of_Iterations: 1 Time_Per_Exposure: 1200S Exposure_Number: 2 Target_Name: IO-LON160 Config: WFPC2 Opmode: IMAGE Aperture: PC1 Sp_Element: F390N Optional_Parameters: ATD-GAIN=15 Number_of_Iterations: 1 Time_Per_Exposure: 70S Exposure_Number: 3 Target_Name: IO-LON160 Config: WFPC2 Opmode: IMAGE Aperture: PC1 Sp_Element: F410M Optional_Parameters: ATD-GAIN=15 Number_of_Iterations: 1 Time_Per_Exposure: 10S Exposure_Number: 4 Target_Name: IO-LON160 Config: WFPC2 Opmode: IMAGE Aperture: PC1 Sp_Element: F467M Optional_Parameters: ATD-GAIN=15 Number_of_Iterations: 1 Time_Per_Exposure: 3.0S Exposure_Number: 5 Target_Name: IO-LON160 Config: WFPC2 Opmode: IMAGE Aperture: PC1 Sp_Element: F791W Optional_Parameters: ATD-GAIN=15 Number_of_Iterations: 1 Time_Per_Exposure: 0.23S Exposure_Number: 6 Target_Name: IO-LON160 Config: WFPC2 Opmode: IMAGE Aperture: PC1 Sp_Element: F502N Optional_Parameters: ATD-GAIN=15 Number_of_Iterations: 1 Time_Per_Exposure: 16S Exposure_Number: 7 Target_Name: IO-LON160 Config: WFPC2 Opmode: IMAGE Aperture: PC1 Sp_Element: F547M Optional_Parameters: ATD-GAIN=15 Number_of_Iterations: 1 Time_Per_Exposure: 0.4S Exposure_Number: 8 Target_Name: IO-LON160 Config: WFPC2 Opmode: IMAGE Aperture: PC1 Sp_Element: F375N Optional_Parameters: ATD-GAIN=15 Number_of_Iterations: 1 Time_Per_Exposure: 500S Exposure_Number: 9 Target_Name: IO-LON160 Config: WFPC2 Opmode: IMAGE Aperture: PC1 Sp_Element: F588N Optional_Parameters: ATD-GAIN=15 Number_of_Iterations: 1 Time_Per_Exposure: 3.0S Exposure_Number: 10 Target_Name: IO-LON160 Config: WFPC2 Opmode: IMAGE Aperture: PC1 Sp_Element: F658N Optional_Parameters: ATD-GAIN=15 Number_of_Iterations: 1 Time_Per_Exposure: 6.0S Exposure_Number: 11 Target_Name: IO-LON160 Config: WFPC2 Opmode: IMAGE Aperture: PC1 Sp_Element: F255W Number_of_Iterations: 1 Time_Per_Exposure: 600S Visit_Number: 3 Exposure_Number: 1 Target_Name: IO-LON250 Config: WFPC2 Opmode: IMAGE Aperture: PC1 Sp_Element: F343N Optional_Parameters: CR-SPLIT=DEF ATD-GAIN=15 Number_of_Iterations: 1 Time_Per_Exposure: 1200S Exposure_Number: 2 Target_Name: IO-LON250 Config: WFPC2 Opmode: IMAGE Aperture: PC1 Sp_Element: F390N Optional_Parameters: ATD-GAIN=15 Number_of_Iterations: 1 Time_Per_Exposure: 70S Exposure_Number: 3 Target_Name: IO-LON250 Config: WFPC2 Opmode: IMAGE Aperture: PC1 Sp_Element: F410M Optional_Parameters: ATD-GAIN=15 Number_of_Iterations: 1 Time_Per_Exposure: 10S Exposure_Number: 4 Target_Name: IO-LON250 Config: WFPC2 Opmode: IMAGE Aperture: PC1 Sp_Element: F467M Optional_Parameters: ATD-GAIN=15 Number_of_Iterations: 1 Time_Per_Exposure: 3.0S Exposure_Number: 5 Target_Name: IO-LON250 Config: WFPC2 Opmode: IMAGE Aperture: PC1 Sp_Element: F791W Optional_Parameters: ATD-GAIN=15 Number_of_Iterations: 1 Time_Per_Exposure: 0.23S Exposure_Number: 6 Target_Name: IO-LON250 Config: WFPC2 Opmode: IMAGE Aperture: PC1 Sp_Element: F502N Optional_Parameters: ATD-GAIN=15 Number_of_Iterations: 1 Time_Per_Exposure: 16S Exposure_Number: 7 Target_Name: IO-LON250 Config: WFPC2 Opmode: IMAGE Aperture: PC1 Sp_Element: F547M Optional_Parameters: ATD-GAIN=15 Number_of_Iterations: 1 Time_Per_Exposure: 0.4S Exposure_Number: 8 Target_Name: IO-LON250 Config: WFPC2 Opmode: IMAGE Aperture: PC1 Sp_Element: F375N Optional_Parameters: ATD-GAIN=15 Number_of_Iterations: 1 Time_Per_Exposure: 500S Exposure_Number: 9 Target_Name: IO-LON250 Config: WFPC2 Opmode: IMAGE Aperture: PC1 Sp_Element: F588N Optional_Parameters: ATD-GAIN=15 Number_of_Iterations: 1 Time_Per_Exposure: 3.0S Exposure_Number: 10 Target_Name: IO-LON250 Config: WFPC2 Opmode: IMAGE Aperture: PC1 Sp_Element: F658N Optional_Parameters: ATD-GAIN=15 Number_of_Iterations: 1 Time_Per_Exposure: 6.0S Exposure_Number: 11 Target_Name: IO-LON250 Config: WFPC2 Opmode: IMAGE Aperture: PC1 Sp_Element: F255W Number_of_Iterations: 1 Time_Per_Exposure: 600S Visit_Number: 4 Exposure_Number: 1 Target_Name: IO-LON340 Config: WFPC2 Opmode: IMAGE Aperture: PC1 Sp_Element: F343N Optional_Parameters: CR-SPLIT=DEF ATD-GAIN=15 Number_of_Iterations: 1 Time_Per_Exposure: 1200S Exposure_Number: 2 Target_Name: IO-LON340 Config: WFPC2 Opmode: IMAGE Aperture: PC1 Sp_Element: F390N Optional_Parameters: ATD-GAIN=15 Number_of_Iterations: 1 Time_Per_Exposure: 70S Exposure_Number: 3 Target_Name: IO-LON340 Config: WFPC2 Opmode: IMAGE Aperture: PC1 Sp_Element: F410M Optional_Parameters: ATD-GAIN=15 Number_of_Iterations: 1 Time_Per_Exposure: 10S Exposure_Number: 4 Target_Name: IO-LON340 Config: WFPC2 Opmode: IMAGE Aperture: PC1 Sp_Element: F467M Optional_Parameters: ATD-GAIN=15 Number_of_Iterations: 1 Time_Per_Exposure: 3.0S Exposure_Number: 5 Target_Name: IO-LON340 Config: WFPC2 Opmode: IMAGE Aperture: PC1 Sp_Element: F791W Optional_Parameters: ATD-GAIN=15 Number_of_Iterations: 1 Time_Per_Exposure: 0.23S Exposure_Number: 6 Target_Name: IO-LON340 Config: WFPC2 Opmode: IMAGE Aperture: PC1 Sp_Element: F502N Optional_Parameters: ATD-GAIN=15 Number_of_Iterations: 1 Time_Per_Exposure: 16S Exposure_Number: 7 Target_Name: IO-LON340 Config: WFPC2 Opmode: IMAGE Aperture: PC1 Sp_Element: F547M Optional_Parameters: ATD-GAIN=15 Number_of_Iterations: 1 Time_Per_Exposure: 0.4S Exposure_Number: 8 Target_Name: IO-LON340 Config: WFPC2 Opmode: IMAGE Aperture: PC1 Sp_Element: F375N Optional_Parameters: ATD-GAIN=15 Number_of_Iterations: 1 Time_Per_Exposure: 500S Exposure_Number: 9 Target_Name: IO-LON340 Config: WFPC2 Opmode: IMAGE Aperture: PC1 Sp_Element: F588N Optional_Parameters: ATD-GAIN=15 Number_of_Iterations: 1 Time_Per_Exposure: 3.0S Exposure_Number: 10 Target_Name: IO-LON340 Config: WFPC2 Opmode: IMAGE Aperture: PC1 Sp_Element: F658N Optional_Parameters: ATD-GAIN=15 Number_of_Iterations: 1 Time_Per_Exposure: 6.0S Exposure_Number: 11 Target_Name: IO-LON340 Config: WFPC2 Opmode: IMAGE Aperture: PC1 Sp_Element: F255W Number_of_Iterations: 1 Time_Per_Exposure: 600S Data_Distribution Medium: 8MM ! 8MM or 6250BPI or 1600BPI Blocking_Factor: 10 ! 10 or 1 Ship_To: PI_Address ! STSCI or PI_Address or Ship_Via: UPS ! UPS (2-day) or OVERNIGHT