! Proposal 6803, submission 1 ! PI: Tilmann Denk ! Received Fri Feb 16 15:04:00 EST 1996 ! From: denk@pavo ! Hubble Space Telescope Cycle 6 (1996) Phase II Proposal Template ! $Id: 6803,v 4.1 1997/09/12 21:36:30 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: Denise Taylor ! Phone: 410-338-4824, E-mail: dctaylor@stsci.edu ! ! Name of Phase I Proposal: archive-1059.denk.prop ! Date generated: Fri Dec 22 18:42:19 EST 1995 ! Proposal_Information ! Section 4 Title: Disk-resolved Spectrophotometry of the Dark Side of Iapetus Proposal_Category: GO Scientific_Category: SOLAR SYSTEM Cycle: 6 Investigators PI_Name: Tilmann Denk PI_Institution: Deutsche Forschungsanstalt fuer Luft- und Raumfahrt CoI_Name: Keith Noll CoI_Institution: Space Telescope Science Institute Contact: N CoI_Name: Dale Cruikshank CoI_Institution: NASA Ames Research Center Contact: N CoI_Name: Ralf Jaumann CoI_Institution: Deutsche Forschungsanstalt fuer Luft- und Raumfahrt Contact: N CoI_Name: Gerhard Neukum CoI_Institution: Deutsche Forschungsanstalt fuer Luft- und Raumfahrt Contact: N CoI_Name: Yvonne Pendleton CoI_Institution: NASA Ames Research Center Contact: N CoI_Name: Ted Roush CoI_Institution: San Francisco State University Contact: N Abstract: ! Free format text (please update) With this HST observation, we will obtain the first spectrum of pure dark material on Iapetus' Cassini Regio from near UV to near IR (320-1040 nm). It will allow us to calibrate higher resolution, earth-based spectra of the leading side of Iapetus. The origin of the dark material on Iapetus is still currently unknown. A direct measurement of the spectrum will allow an unbiased comparison of Cassini Regio with spectra of laboratory samples and spectra of other outer solar system objects and therefore offer an additional key to the origin question. We will image the leading hemisphere of Iapetus in 11 narrow band filters. We will observe at eastern elongation when the visible disk is most completely covered by the dark material with the minimum coverage by bright polar ice. Near opposition Iapetus will have an angular diameter of 0.23", or more than 5 PC-pixels. This is sufficient for disk-resolved spectrophotometry of Cassini Regio. HST is the only astronomical instrument capable of this observation. Questions ! Free format text (please update) Observing_Description: We propose to get spectrophotometry of Iapetus by imaging with WFPC2 at 11 different wavelengths (Table). The following criteria have been used for the Phase-II filter selection: - Choice of filters with central wavelengths comparable to Voyager-ISS filters (for shorter wavelengths). - Choice of filters with longer central wavelengths for search of spectral features of water ice. - Continuous steps throughout the WFPC2 wavelength range as far as limited observing time allows. One image offset by half pixel step will be obtained for one or two filters (F410M and possibly F656N) in order to evaluate effects of pixelization. Table: Iapetus HST observation filter set and exposure times. Count rate HST exp. Filter D [e-/(sec*pxl)] time [sec] -------- - -------------- ---------- F336W* 13 200 F410M* x 14 180 F467M* 38 70 LRF554* 27 100 F588N* 55 50 F656N (x) 21 140 LRF763 55 50 LRF835 43 60 FQCH4P15 20 140 F953N 9.4 300 F1042M 10 260 -------- - -------------- ---------- * = Relation to Voyager filter D = Dither image LRF554 designates the linear ramp filter at a wavelength of 554 nm. The two other LRF entries have a similar meaning. All LRF wavelengths were chosen to fall of the PC. The SNR will be about 50 for all images (dark area). For the bright polar regions, the SNR will be more than 200. The ADU (for gain=14) will be about 200 for "Cassini Regio pixels", and approximately 3000 for "polar pixels". Real_Time_Justification: We require observation within 1 day of Iapetus eastern elongation. Because of the small angular size of Iapetus, we also require observations close to opposition. One such opportunity in cycle 6 will occur on 01 September 1996. Calibration_Justification: ! Move appropriate text from Real_Time_Just. None. Additional_Comments: Justification for: Solar_System_Targets, Window: CML OF IAPETUS FROM EARTH BETWEEN 85 95: Observation of the DARK SIDE of IAPETUS - CASSINI REGIO - when as much as possible of this area is visible for HST, and when as few as possible of the bright surrounding terrain is visible. Justification for: Visit_Requirements: BETWEEN 16-AUG-1996 AND 06-NOV-1996: Best opportunity for HST imaging of Iapetus will be close to Saturn opposition (26-SEP-1996 during Cycle 6). Iapetus has a revolution period of nearly 80 days. Therefore, a time span of 40 days before and after opposition will provide by far the best observing conditions. Solar_System_Targets ! Section 5.2 Target_Number: 1 Target_Name: IAPETUS-CASSINI-REGIO Description: FEATURE IAPETUS Level_1: STD=SATURN ! Satellite of Sun Level_2: STD=IAPETUS ! Satellite of Saturn Level_3: TYPE=PGRAPHIC ! Surface Feature on Iapetus LONG=90 LAT=0 Ephem_Uncert: Acq_Uncert: Window: CML OF IAPETUS FROM EARTH BETWEEN 85 95 Flux: SURF(V)=12.2+/-0.5 ! Include at least V and B-V Comments: None. Visits ! Section 6 Visit_Number: 1 Visit_Requirements: BETWEEN 1-NOV-1998 AND 15-NOV-1998 On_Hold_Comments: Visit_Comments: [1] If expanding of exposure time is possible, expand all images of each orbit proportionally to fill the orbit. [2] If the 13 proposed exposures (11 exposures, two of them with 'dither' parameter) cannot be fitted into the two allocated orbits, the following rules should be used: 2A) Change the exposure numbers in order to find a sequence which fits into the two orbits (and which could not have been found by using RPS2). If this doesn't work: 2B) Reduce the exposure times if necessary, but by no more than 20%. It is not necessary to reduce them proportionally, although this might be preferred. A reduction of exposure times for the longer exposures combined with a change of the gain state may also be considered. If this doesn't work, too: 2C) Remove the dither option of exposure no. 231 (filter F656N). Exposure_Number: 13 Target_Name: IAPETUS-CASSINI-REGIO Config: WFPC2 Opmode: IMAGE Aperture: PC1 Sp_Element: F336W Wavelength: 3342 Optional_Parameters: ATD-GAIN=15 Number_of_Iterations: 1 Time_Per_Exposure: 200S Special_Requirements: Exposure_Number: 25 Target_Name: IAPETUS-CASSINI-REGIO Config: WFPC2 Opmode: IMAGE Aperture: PC1 Sp_Element: F410M Wavelength: 4090 Optional_Parameters: ATD-GAIN=15 DITHER-TYPE=LINE Number_of_Iterations: 1 Time_Per_Exposure: 180S Special_Requirements: Exposure_Number: 12 Target_Name: IAPETUS-CASSINI-REGIO Config: WFPC2 Opmode: IMAGE Aperture: PC1 Sp_Element: F467M Wavelength: 4669 Optional_Parameters: ATD-GAIN=15 Number_of_Iterations: 1 Time_Per_Exposure: 70S Special_Requirements: Exposure_Number: 22 Target_Name: IAPETUS-CASSINI-REGIO Config: WFPC2 Opmode: IMAGE Aperture: LRF Sp_Element: LRF Wavelength: 5540 Optional_Parameters: ATD-GAIN=15 Number_of_Iterations: 1 Time_Per_Exposure: 100S Special_Requirements: Exposure_Number: 11 Target_Name: IAPETUS-CASSINI-REGIO Config: WFPC2 Opmode: IMAGE Aperture: PC1 Sp_Element: F588N Wavelength: 5894 Optional_Parameters: ATD-GAIN=15 Number_of_Iterations: 1 Time_Per_Exposure: 50S Special_Requirements: Exposure_Number: 231 Target_Name: IAPETUS-CASSINI-REGIO Config: WFPC2 Opmode: IMAGE Aperture: PC1 Sp_Element: F656N Wavelength: 6564 Optional_Parameters: ATD-GAIN=15 DITHER-TYPE=LINE Number_of_Iterations: 1 Time_Per_Exposure: 140S Special_Requirements: Comments: If the proposed observations can not be executed within the two allocated orbits, the 'dither' option of this exposure might be sacrified. Exposure_Number: 23 Target_Name: IAPETUS-CASSINI-REGIO Config: WFPC2 Opmode: IMAGE Aperture: LRF Sp_Element: LRF Wavelength: 7630 Optional_Parameters: ATD-GAIN=15 Number_of_Iterations: 1 Time_Per_Exposure: 50S Special_Requirements: Exposure_Number: 24 Target_Name: IAPETUS-CASSINI-REGIO Config: WFPC2 Opmode: IMAGE Aperture: LRF Sp_Element: LRF Wavelength: 8350 Optional_Parameters: ATD-GAIN=15 Number_of_Iterations: 1 Time_Per_Exposure: 60S Special_Requirements: Exposure_Number: 16 Target_Name: IAPETUS-CASSINI-REGIO Config: WFPC2 Opmode: IMAGE Aperture: FQCH4P15 Sp_Element: FQCH4P15 Wavelength: 8929 Optional_Parameters: ATD-GAIN=15 Number_of_Iterations: 1 Time_Per_Exposure: 140S Special_Requirements: Exposure_Number: 15 Target_Name: IAPETUS-CASSINI-REGIO Config: WFPC2 Opmode: IMAGE Aperture: PC1 Sp_Element: F953N Wavelength: 9545 Optional_Parameters: ATD-GAIN=15 Number_of_Iterations: 1 Time_Per_Exposure: 300S Special_Requirements: Exposure_Number: 14 Target_Name: IAPETUS-CASSINI-REGIO Config: WFPC2 Opmode: IMAGE Aperture: PC1 Sp_Element: F1042M Wavelength: 10184 Optional_Parameters: ATD-GAIN=15 Number_of_Iterations: 1 Time_Per_Exposure: 260S Special_Requirements: Data_Distribution ! 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