! +====================+ ! | PED OUTPUT PRODUCT | ! +====================+ ! ! /spectre/data1/aroman/proposals/6755.prop ! Generated by PREPROCESSOR, version 6.4b ! Date: Tue Aug 20 10:44:25 EDT 1996 Proposal_Information Title: Morphology of OH in the Saturn Magnetsophere Proposal_Category: GO Scientific_Category: SOLAR SYSTEM Cycle: 6 Investigators PI_Name: Donald E. Shemansky PI_Institution: University of Southern California CoI_Name: Philip L. Matheson CoI_Institution: University of Southern California Contact: CoI_Name: Doyle T. Hall CoI_Institution: Johns Hopkins University Contact: CoI_Name: Michel Festou CoI_Institution: Obervatoire Midi-Pyrenees Contact: Abstract: A total of 17 orbits is requested for exploration of the Saturn magnetosphere to define the morphology of OH discovered in August 1992 in GO3644, and observed again in December 1994 (GO5391). These HST FOS observations definitively established the fact that neutral gas dominates the magnetosphere, with a mixing ratio to ions over the range 15 in 1992 to greater than 100 in 1994, whereas previous theory was dependent on mixing ratios < 0.05. The change in brightness between the FOS 1992 and 1994 observations and incompatibility with the Voyager plasma model, taken together, strongly suggest that the neutral content of the magnetosphere is significantly temporally variable. Theoretical calculations of source rates cannot account for the large values inferred from the observations. These considerations indicate that the phenomenon, which obviously has a profound effect on the magnetosphere, is not understood at a first order level. We therefore propose further HST FOS observations in an attempt to set limits on source properties, and obtain additional morphological information that only HST can provide. The observation plan is to obtain 1) a direct limit on source strength at the satellite Tethys, 2) a measure of abundance at 3 R_S, the nearest point to Saturn now considered the practical limit for observation, and 3) a measure of latitudinal extent of the neutral gas that has not been previously obtained. The measurements are expected to greatly facilitate experiment strategy for the Cassini Mission. Questions Observing_Description: SATURN-TORUS (a) Observation of OH 3085 Angstrom emission at 4.5 R_S in orbital plane on dusk side. (b) FOS/RD, G270H, A-1 aperture, IMAGE, 3 orbits. (c) Time critical, between Sept 06 and Oct 31, 1996. (d) Line of sight must intersect major axis of satellite orbital plane. Line of sight must be well clear of satellite bodies. (e) Three IMAGE positions; center, and extreme upper and lower. Exposures equal in each position, commutated within each orbit. (f) Estimated exposure time based on 100 R emission observed in Dec 1994. (g) Observation at 4.5 R_S is repeated from Dec 1994 with larger aperture, because of strong indication of temporal variability. SATURN-TORUS-HEIGHT (a) Observation of OH 3085 Angstrom emission at 4.5 R_S out of plane on dusk side. (b) FOS/RD, G270H, A-1 aperture, IMAGE, 5 orbits. (c) Time critical, between Sept 06 and Oct 31, 1996. (d) Line of sight must lie 3.7 arcsec above major axis of satellite orbital plane. Line of sight must be well clear of satellite bodies. (e) Two IMAGE positions; center, and extreme upper. Exposures equal in each position, commutated within each orbit. (f) Estimated exposure time based on assumption of unknown latitudinal scale height of torus emission. (g) This will provide first measurement of latitudinal scale. TETHYS (a) Observation of OH 3085 Angstrom emission from Tethys in orbital plane on dusk side of Saturn. (b) FOS/RD, G270H, 2.0-BAR aperture, IMAGE, 4 orbits, Tethys occulted. One orbit with 1.0-PAIR-A on Tethys directly. (c) Time critical, between Sept 06 and Oct 31, 1996. (d)Exposures begin with Tethys - 30 degrees from ansa, and end five HST orbits later with Tethys ~ +30 degrees from ansa. Tethys occulted by 2.0-Bar for 4 orbit duration. (e) These measurements are expected to provide evidence on the magnitude of the water product source at Tethys. SATURN-RINGS-TORUS (a) Observation of OH 3085 Angstrom\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\ emission at 3.0 R_S in orbital plane on dusk side. (b) FOS/RD, G270H, A-1 aperture, IMAGE, 3 orbits, (c) Time critical, between Sept 06 and Oct 31, 1996. (d) Line of sight must intersect major axis of satellite orbital plane. Line of sight must be well clear of satellite bodies. (e) Three IMAGE positions; center, and extreme upper and lower. Exposures equal in each position, commutated within each orbit. (f) This position is considered to be the practical limit for observations, based on estimated off axis scattered background signal, and is intended to provide a measure of distribution toward vicinity of rings. Real_Time_Justification: Observations must be made during opposition, Sept 16 -- Oct 31 1996, in order to allow rotation of aperture to specified alignment with the Saturn system. Investigators in this program (Festou, Shemansky, Matheson) obtained telescope time on IUE for observations of the Saturn magnetosphere in the fall of 1995. This attempt is regarded as complementary to the HST effort, because IUE does not have comparable spatial resolution and pointing stability to define what may be a gas cloud sharply confined to the satellite orbital plane. The evidence for temporal variability indicates that observations should be made as frequently as possible to provide an understanding of source processes. Calibration_Justification: Additional_Comments: Fixed_Targets Solar_System_Targets Target_Number: 1 Target_Name: SATURN-TORUS Description: TORUS SATURN Level_1: STD=SATURN Level_2: TYPE=TORUS,LONG=90,LAT=0,RAD=2.72E05,POLE_LAT=+90 Level_3: Window: SEP OF SATURN-TORUS TETHYS FROM EARTH GT 5", SEP OF SATURN-TORUS DIONE FROM EARTH GT 5", SEP OF SATURN-TORUS RHEA FROM EARTH GT 5", SEP OF SATURN-TORUS TITAN FROM EARTH GT 5" Flux: SURF-CONT(3085)=7.7+/-3.e-16 Comments: Western Ansa at 4.5 R_S. This reproduces exposures made in 92 and 94 Target_Number: 2 Target_Name: SATURN-TORUS-HEIGHT Description: TORUS SATURN Level_1: STD=SATURN Level_2: TYPE=TORUS,LONG=+90,LAT=+5.44,RAD=2.72E05,POLE_LAT=+90 Level_3: Window: SEP OF SATURN-TORUS TETHYS FROM EARTH GT 5", SEP OF SATURN-TORUS DIONE FROM EARTH GT 5", SEP OF SATURN-TORUS RHEA FROM EARTH GT 5", SEP OF SATURN-TORUS TITAN FROM EARTH GT 5" Flux: SURF-CONT(3085)=7.7+/-3.e-16 Comments: FOV is out of orbital plane in order to observe latitudinal distribution of OH Target_Number: 3 Target_Name: TETHYS Description: SATELLITE TETHYS Level_1: STD=SATURN Level_2: STD=TETHYS Level_3: Window: OLG OF TETHYS BETWEEN 238 300 Flux: V = 10.2 B-V = 0.73 Comments: TO OBSERVE SOURCE PROCESS NEAR TETHYS Target_Number: 4 Target_Name: SATURN-RINGS-TORUS Description: RING SATURN Level_1: STD=SATURN Level_2: TYPE=TORUS,LONG=90,LAT=0,RAD=1.82E05,POLE_LAT=+90 Level_3: Window: SEP OF SATURN-TORUS ENCELADUS FROM EARTH GT 5", SEP OF SATURN-TORUS TETHYS FROM EARTH GT 5", SEP OF SATURN-TORUS DIONE FROM EARTH GT 5", SEP OF SATURN-TORUS RHEA FROM EARTH GT 5", SEP OF SATURN-TORUS TITAN FROM EARTH GT 5" Flux: SURF-CONT-BKG(3085)=1.7+/-3.e-15 Comments: LARGE SOLAR SCATTERING BACKGROUND FROM SATURN EXPECTED. Target_Number: 5 Target_Name: RHEA-OFFSET Description: SATELLITE RHEA Level_1: STD=SATURN Level_2: STD=RHEA Level_3: Window: Flux: V = 9.7 B-V = 0.78 Comments: USE FOR ACQUISITION FOR TARGET 1 AND 2, BY OFFSETING FROM RHEA Generic_Targets Scan_Data Visits Visit_Number: 01 Visit_Requirements: ORIENT 75D TO 95D SCHED 100% BETWEEN 06-Sep-1996 AND 31-Oct-1996 On_Hold_Comments: Visit_Comments: ORIENT is used to align FOS X-axis in the orbital plane of the satellites. FOS Y-axis should be along Saturn`s spin axis Exposure_Number: 1 Target_Name: RHEA-OFFSET Config: FOS/RD Opmode: ACQ/PEAK Aperture: 4.3 Sp_Element: G270H Wavelength: Optional_Parameters: SEARCH-SIZE-X=1,SEARCH-SIZE-Y=3,SCAN-STEP-Y=1.23 Number_of_Iterations: 1 Time_Per_Exposure: 10 S Special_Requirements: ONBOARD ACQ FOR 2-3 Comments: ACQUIRE RHEA AND OFFSET TO TORUS POSITION Exposure_Number: 2 Target_Name: RHEA-OFFSET Config: FOS/RD Opmode: ACQ/PEAK Aperture: 1.0 Sp_Element: G270H Wavelength: Optional_Parameters: SEARCH-SIZE-X=6,SEARCH-SIZE-Y=2,SCAN-STEP-X=.61,SCAN-STEP-Y=.61 Number_of_Iterations: 1 Time_Per_Exposure: 10 S Special_Requirements: ONBOARD ACQ FOR 3-4 Comments: ACQUIRE RHEA AND OFFSET TO TORUS POSITION Exposure_Number: 3 Target_Name: SATURN-TORUS Config: FOS/RD Opmode: IMAGE Aperture: 4.3 Sp_Element: G270H Wavelength: 3085 Optional_Parameters: SUB-STEP=4,COMB=YES,Y-SPACE=256,Y-SIZE=3 Number_of_Iterations: 1 Time_Per_Exposure: 96 M Special_Requirements: Comments: Exposure_Number: 4 Target_Name: SATURN-TORUS-HEIGHT Config: FOS/RD Opmode: IMAGE Aperture: 4.3 Sp_Element: G270H Wavelength: Optional_Parameters: SUB-STEP=4,COMB=YES,Y-OFFSET=-128,Y-SPACE=256,Y-SIZE=2 Number_of_Iterations: 1 Time_Per_Exposure: 9010 S Special_Requirements: Comments: Diodes should be mapped along bottom 1/3 and central 1/3 of aperture Visit_Number: 02 Visit_Requirements: ORIENT 70D TO 95D SCHED 100% BETWEEN 06-Sep-1996 AND 31-Oct-1996 GUID TOL 2.1" On_Hold_Comments: Visit_Comments: ORIENT is used to align FOS X-axis in orbital plane of satellites. FOS Y-axis should be along Saturn's spin axis Exposure_Number: 5 Target_Name: TETHYS Config: FOS/RD Opmode: ACQ/PEAK Aperture: 4.3 Sp_Element: G270H Wavelength: Optional_Parameters: SEARCH-SIZE-X=1,SEARCH-SIZE-Y=3,SCAN-STEP-Y=1.23 Number_of_Iterations: 1 Time_Per_Exposure: 1 S Special_Requirements: ONBOARD ACQ FOR 6 Comments: ACQUIRE TETHYS AND OFFSET TO TORUS POSITION FOR OBSERVATION OF SATURN-RINGS-TORUS Exposure_Number: 6 Target_Name: TETHYS Config: FOS/RD Opmode: ACQ/PEAK Aperture: 1.0 Sp_Element: G270H Wavelength: Optional_Parameters: SEARCH-SIZE-X=6,SEARCH-SIZE-Y=2,SCAN-STEP-X=0.61,SCAN-STEP-Y=0.61 Number_of_Iterations: 1 Time_Per_Exposure: 1 S Special_Requirements: ONBOARD ACQ FOR 8 Comments: ACQUIRE TETHYS Exposure_Number: 8 Target_Name: TETHYS Config: FOS/RD Opmode: ACQ/PEAK Aperture: 0.3 Sp_Element: G270H Wavelength: Optional_Parameters: SEARCH-SIZE-X=5,SEARCH-SIZE-Y=5,SCAN-STEP-X=0.172,SCAN-STEP-Y=0.172 Number_of_Iterations: 1 Time_Per_Exposure: 1 S Special_Requirements: ONBOARD ACQ FOR 9 Comments: ACQUIRE TETHYS Exposure_Number: 9 Target_Name: TETHYS Config: FOS/RD Opmode: ACQ/PEAK Aperture: 2.0-BAR Sp_Element: G270H Wavelength: Optional_Parameters: SEARCH-SIZE-X=1,SEARCH-SIZE-Y=11,SCAN-STEP-X=0,SCAN-STEP-Y=0.052,TYPE=DOWN Number_of_Iterations: 1 Time_Per_Exposure: 1 S Special_Requirements: ONBOARD ACQ FOR 10-12 SEQ 9-10 NON-INT Comments: ACQUIRE TETHYS Exposure_Number: 10 Target_Name: TETHYS Config: FOS/RD Opmode: ACCUM Aperture: 2.0-BAR Sp_Element: G270H Wavelength: 3085 Optional_Parameters: Number_of_Iterations: 1 Time_Per_Exposure: 24 M Special_Requirements: Comments: TETHYS SHOULD BE TRAVERSING DUSK ANSA. TETHYS SHOULD BE OCCULTED BY BAR Exposure_Number: 11 Target_Name: TETHYS Config: FOS/RD Opmode: ACCUM Aperture: 2.0-BAR Sp_Element: G270H Wavelength: 3085 Optional_Parameters: Number_of_Iterations: 1 Time_Per_Exposure: 100 M Special_Requirements: Comments: TETHYS SHOULD BE TRAVERSING DUSK ANSA. TETHYS SHOULD BE OCCULTED BY BAR Exposure_Number: 12 Target_Name: SATURN-RINGS-TORUS Config: FOS/RD Opmode: IMAGE Aperture: 4.3 Sp_Element: G270H Wavelength: 3085 Optional_Parameters: COMB=YES,SUB-STEP=4,Y-SPACE=256,Y-SIZE=3 Number_of_Iterations: 1 Time_Per_Exposure: 100 M Special_Requirements: EXPAND Comments: OFFSET TO TORUS POSITION FOR OBSERVATION OF SATURN-RINGS-TORUS Visit_Number: 03 Visit_Requirements: ORIENT 75D TO 95D SCHED 100% BETWEEN 06-Sep-1996 AND 31-Oct-1996 On_Hold_Comments: Visit_Comments: This visit to fill out 17th orbit. Exposure_Number: 9 Target_Name: TETHYS Config: FOS/RD Opmode: ACQ/PEAK Aperture: 4.3 Sp_Element: G270H Wavelength: Optional_Parameters: SEARCH-SIZE-X=1,SEARCH-SIZE-Y=3,SCAN-STEP-Y=1.23 Number_of_Iterations: 1 Time_Per_Exposure: 1 S Special_Requirements: ONBOARD ACQ FOR 10 Comments: Exposure_Number: 10 Target_Name: TETHYS Config: FOS/RD Opmode: ACQ/PEAK Aperture: 1.0 Sp_Element: G270H Wavelength: Optional_Parameters: SEARCH-SIZE-X=6,SEARCH-SIZE-Y=2,SCAN-STEP-X=0.61,SCAN-STEP-Y=0.61 Number_of_Iterations: 1 Time_Per_Exposure: 1 S Special_Requirements: ONBOARD ACQ FOR 11 Comments: Exposure_Number: 11 Target_Name: TETHYS Config: FOS/RD Opmode: ACCUM Aperture: 1.0-PAIR-A Sp_Element: G270H Wavelength: 3085 Optional_Parameters: Number_of_Iterations: 1 Time_Per_Exposure: 10 M Special_Requirements: NO SPLIT MAX DUR 100% Comments: TETHYS SHOULD BE TRAVERSING DUSK ANSA. THE DIODES SHOULD BE DEFLECTED SO THAT THEY ARE DIRECTLY UNDER THE 1.0-PAIR-A APERTURE Data_Distribution ! 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