! Proposal 5837, submission 1 ! PI: Keith S. Noll ! Received Thu Feb 16 12:10:42 EST 1995 ! From: noll@stsci.edu ! Hubble Space Telescope Cycle 5 (1995) Phase II Proposal Template ! $Id: 5837,v 7.1 1995/08/14 14:12:37 pepsa Exp $ ! ! Refer to the HST Phase II Proposal Instructions to fill this out ! ! Anything after a "!" is ignored, and may be deleted ! ! All keywords with multiple entries are comma delimited except the ! Visit_Requirements and Special_Requirements keywords which can be ! delimited with carriage returns or semi-colons, but not commas ! ! For help call your Program Coordinator: Andy Lubenow ! Phone: 410 338-4928 , E-mail: lubenow@stsci.edu ! ! This partially completed template was generated from a Phase I proposal. ! Name of Phase I Proposal: noll-909.prop ! Date generated: Fri Dec 16 15:08:40 EST 1994 ! Proposal_Information ! Section 4 Title: Ultraviolet Imaging and Spectroscopy of the Icy Galilean Satellites Proposal_Category: GO Scientific_Category: Solar System Cycle: 5 Investigators PI_name: Keith S. Noll PI_Institution: Space Telescope Science Institute CoI_Name: Bonnie Buratti CoI_Institution: Jet Propoulsion Laboratory Contact: ! Y or N (designate at most one contact) CoI_Name: Deborah Domingue CoI_Institution: Lunar and Planetary Institute Contact: ! Y or N (designate at most one contact) CoI_Name: Robert Johnson CoI_Institution: University of Virginia Contact: ! Y or N (designate at most one contact) CoI_Name: Arthur L. Lane CoI_Institution: Jet Propulsion Laboratory Contact: ! Y or N (designate at most one contact) CoI_Name: Melissa McGrath CoI_Institution: Space Telescope Science Institute Contact: ! Y or N (designate at most one contact) CoI_Name: Paola Sartoretti CoI_Institution: Space Telescope Science Institute Contact: ! Y or N (designate at most one contact) CoI_Name: Harold A. Weaver CoI_Institution: Space Telescope Science Institute Contact: ! Y or N (designate at most one contact) Abstract: ! Free format text (please update) We will obtain the first ultraviolet images of the three icy Galilean satellites, Europa, Ganymede, and Callisto, with the HST WFPC2. No other observatory or spacecraft has been or will be capable of obtaining resolved images of Jupiter's large satellites at wavelengths below 3200 Angstrom . Strong UV bands of SO2 and other spectral features caused by charged particle impacts in ice produce significant albedo effects in this part of the spectrum. Correlation of UV albedo maps to visible geologic features will allow us to investigate both internal and external processes that modify these surfaces. We will also obtain high S/N spectra of all three satellites from 1800-3300 Angstrom , including the first useable spectra ever below 2400 Angstrom . The FOS spectra are of sufficiently high resolution that we will be able to distinguish between different compositional and physical states of the surfaces. The spectra will also improve the interpretation of the images. Our program of imaging and spectroscopy will be coordinated with a series of `final' IUE and groundbased near-UV observations to be executed prior to the Galileo encounter with the Jovian system. The measurements will provide the temporal tie between 15-plus years of IUE spectroscopy and the HST/Galileo epoch and, more importantly, will shape the priorities for the Galileo satellite encounters on that now bandwidth-limited mission. Questions ! Free format text (please update) Observing_Description: The HST is the only instrument capable of obtaining spatially resolved images of Europa, Ganymede, and Callisto in the UV for the forseeable future. The imaging experiments on the Galileo spacecraft which will arrive at Jupiter in 1995 extend only to 3800 Angstrom (Yeates et al. 1985). Ground based observations are limited to the spectral range longer than ~ 3200 Angstrom . The Voyager UV filter was similarly limited to wavelengths longward of 3500 Angstrom . HST is also capable of obtaining high S/N and high spectral resolution UV spectra with short integration times. These data will be used to determine surface composition, help in the analysis of WFPC2 images with filter bandpasses in the UV, and will be conveyed to the Galileo science team in order to assist in difficult decisions regarding data retrieval. Our observing plan is to repeat identical four-orbit observing sequences for Europa, Ganymede, and Callisto. We will use the sequence once for the trailing hemisphere of each satellite (near western elongation) and once for the leading hemisphere of each satellite (near eastern elongation) for a total of twenty four orbits. The four orbit sequence consists of two orbits of WFPC2 observations followed by two orbits of FOS spectroscopy. The observation sequence will begin in the first orbit with a full guide star acquisition followed by exposures in the UV (F255W, F300W, F336W), blue (F439W), green (F555W), and red (F675W) filters. The exposure times needed for S/N >= 100 per pixel are seconds in the cases of the visible wavelength filters which will be used to make composite images required for correlating UV features to visible albedo features. The exposure times needed for the UV filters are given in the table. For the two shortest filters we tabulate the number of electrons collected per pixel in 1000 seconds (F218W) and 100 seconds (F255W). For the two longer UV filters we compute the time to accumulate 15,000 electrons (S/N ~ 122). The key observations in the F218W filter take place in the second orbit in the sequence after a guide star reaquisition, allowing us the maximum integration time. We will obtain two 1000 second integrations at F218W which should yield S/N >= 18 per pixel. Long integrations accumulate many cosmic rays so two are required to allow us to efficiently remove their effects (we will not use CR-SPLIT on individual integrations). The third orbit will begin with a full guide star acquisition and then use the FOS ACQ/PEAK onboard software for target acquisition. ACQ/PEAK has recently been upgraded to allow acquisitions of bright moving targets in the FOS, something that was not possible before. Unfortunately, the search routine is time consuming and uses the remainder of the orbit. After a reacquisition in the fourth orbit, FOS/RD spectra with the G270H and G190H will be obtained. Integration times of 5 minutes (G270H) and 20 minutes (G190H) achieve S/N >= 10 for all wavelengths longer than 1950 Angstrom for all satellites. Because of the steepness of the solar continuum the S/N is considerably higher at the long wavelength end of each grating. For the dark trailing hemisphere of Europa (where we have measured the flux down to 2200 Angstrom ) the S/N in the G190H grating ranges from 5 at 1800 Angstrom to 122 at 2300 Angstrom , in the G270H grating the S/N is 50 at 2200 Angstrom and 350 at 3300 Angstrom . Callisto and Ganymede are fainter, in part because they overfill the aperture. The S/N for the dark leading hemisphere of Callisto, the darkest of all six hemispheres, will be lower by as much as a factor of 0.4 at all wavelengths. Real_Time_Justification: Our highest priority is to execute the observations in time (summer 1995) to assist the Galileo team in deciding priorities for the limited amount of science data that will be returned. We prefer observations near opposition when we obtain the best image scale and in order to obtain low phase angle observations that will complement the higher phase angle observations Galileo will make. Team member A. Lane is the principal investigator for satellite surfaces on the Galileo UVS experiment. He will be the primary point of contact between our investigative team and the Galileo project. We plan to make information available as quickly as possible to aid the Galileo team in selecting target sequences and in prioritizing data retrieval. Team members A. Lane and D. Domingue will also be responsible for leading both IUE and ground based spectroscopic observations that will concentrate on the long wavelength portion of the UV. Calibration_Justification: ! Move appropriate text from Real_Time_Justification Additional_Comments: Solar_System_Targets ! Section 5.2 Target_Number: 1 Target_Name: Europa-East Description: satellite Europa Level_1: STD = Jupiter ! Satellite of Sun Level_2: STD = Europa ! Satellite of Level_1 Level_3: ! Satellite of Level_2 Window: OLG of Europa from Earth between 70 110 Flux: V = 5.29 ! Include at least V and B-V B-V = 0.87 Comments: Target_Number: 2 Target_Name: Europa-West Description: satellite Europa Level_1: STD = Jupiter Level_2: STD = Europa Level_3: Window: OLG of Europa from Earth between 250 290 Flux: V = 5.29 B-V = 0.87 Comments: Target_Number: 3 Target_Name: Ganymede-East Description: satellite Ganymede Level_1: STD = Jupiter Level_2: STD = Ganymede Level_3: Window: OLG of Ganymede from Earth between 70 110 Flux: V = 4.61 B-V = 0.83 Comments: Target_Number: 4 Target_Name: Ganymede-West Description: satellite Ganymede Level_1: STD = Jupiter Level_2: STD = Ganymede Level_3: Window: OLG of Ganymede from Earth between 250 290 Flux: V = 4.61 B-V = 0.83 Comments: Target_Number: 5 Target_Name: Cal-Gany-W Description: satellite Ganymede Level_1: STD = Jupiter Level_2: STD = Ganymede Level_3: Window: OLG of Ganymede from Earth between 240 300 , SEP OF GANYMEDE CALLISTO FROM EARTH LT 100", A_VEL CALLISTO RELATIVE GANYMEDE FROM EARTH LT 0.0007 Flux: V = 4.61 B-V = 0.83 Comments: Both Callisto and Ganymede must be on WFPC Target_Number: 6 Target_Name: Cal-Gany-E Description: satellite Callisto Level_1: STD = Jupiter Level_2: STD = Callisto Level_3: Window: OLG of Ganymede from Earth between 60 120 , SEP OF GANYMEDE CALLISTO FROM EARTH LT 100", A_VEL CALLISTO RELATIVE GANYMEDE FROM EARTH LT 0.0007 Flux: V = 5.65 B-V = 0.86 Comments: Both Callisto and Ganymede must be on WFPC Visits Visit_Number: 1 Visit_Requirements: BEFORE 16-OCT-95 ! PCS MODE [Fine | Gyro] ! ORIENTation TO FROM NOMINAL ! GROUP WITHIN