6755( 21) - 08/20/96 10:47 - [ 0] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 6755 Version: 21 Check-in Date: 20-Aug-1996 10:45:04 1.Proposal Title: Morphology of OH in the Saturn Magnetsophere ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Cycle SOLAR SYSTEM GO 6 ------------------------------------------------------------------------------------ 5. Investigators Contact? PI: Donald E. Shemansky University of Southern California CoI: Philip L. Matheson University of Southern California N CoI: Doyle T. Hall Johns Hopkins University N CoI: Michel Festou Obervatoire Midi-Pyrenees N ------------------------------------------------------------------------------------ 6. 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. ------------------------------------------------------------------------------------ Observations 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 ------------------- ------------------------------------------------------------------------------------ Data Distribution Media: 8MM Blocking Factor: 10 Ship To: PI_Address Ship Via: UPS Email: , ------------------------------------------------------------------------------------ 6755( 21) - 08/20/96 10:47 - [ 1] TARGET LIST b)Solar System Targets ------------------------------------------------------------------------------------------------------------------------------------ TARGET NUMBER: 1 | TARGET NAME: SATURN-TORUS ------------------------------------------------------------------------------------------------------------------------------------ TARGET DESCRIPTION: TORUS SATURN ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 1 | TARGET POSITION LEVEL 2 | STD=SATURN | TYPE=TORUS,LONG=90,LAT=0,RAD=2.72E05,POL | E_LAT=+90 | ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 3 | WINDOWS | | 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" | ------------------------------------------------------------------------------------------------------------------------------------ DATA | COMMENTS | SURF-CONT(3085)=7.7+/-3.e-16 | Western Ansa at 4.5 R_S. This | reproduces exposures made in 92 and | 94 | ------------------------------------------------------------------------------------------------------------------------------------ TARGET NUMBER: 2 | TARGET NAME: SATURN-TORUS-HEIGHT ------------------------------------------------------------------------------------------------------------------------------------ TARGET DESCRIPTION: TORUS SATURN ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 1 | TARGET POSITION LEVEL 2 | STD=SATURN | TYPE=TORUS,LONG=+90,LAT=+5.44,RAD=2.72E0 | 5,POLE_LAT=+90 | ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 3 | WINDOWS | | 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" | ------------------------------------------------------------------------------------------------------------------------------------ DATA | COMMENTS | SURF-CONT(3085)=7.7+/-3.e-16 | FOV is out of orbital plane in order | to observe latitudinal distribution | of OH | ------------------------------------------------------------------------------------------------------------------------------------ 6755( 21) - 08/20/96 10:47 - [ 2] TARGET LIST b)Solar System Targets ------------------------------------------------------------------------------------------------------------------------------------ TARGET NUMBER: 3 | TARGET NAME: TETHYS ------------------------------------------------------------------------------------------------------------------------------------ TARGET DESCRIPTION: SATELLITE TETHYS ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 1 | TARGET POSITION LEVEL 2 | STD=SATURN | STD=TETHYS | ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 3 | WINDOWS | | OLG OF TETHYS BETWEEN 238 300 | ------------------------------------------------------------------------------------------------------------------------------------ DATA | COMMENTS | V = 10.2 | TO OBSERVE SOURCE PROCESS NEAR B-V = 0.73 | TETHYS | ------------------------------------------------------------------------------------------------------------------------------------ TARGET NUMBER: 4 | TARGET NAME: SATURN-RINGS-TORUS ------------------------------------------------------------------------------------------------------------------------------------ TARGET DESCRIPTION: RING SATURN ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 1 | TARGET POSITION LEVEL 2 | STD=SATURN | TYPE=TORUS,LONG=90,LAT=0,RAD=1.82E05,POL | E_LAT=+90 | ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 3 | WINDOWS | | 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" | ------------------------------------------------------------------------------------------------------------------------------------ DATA | COMMENTS | SURF-CONT-BKG(3085)=1.7+/-3.e-15 | LARGE SOLAR SCATTERING BACKGROUND | FROM SATURN EXPECTED. | ------------------------------------------------------------------------------------------------------------------------------------ 6755( 21) - 08/20/96 10:47 - [ 3] TARGET LIST b)Solar System Targets ------------------------------------------------------------------------------------------------------------------------------------ TARGET NUMBER: 5 | TARGET NAME: RHEA-OFFSET ------------------------------------------------------------------------------------------------------------------------------------ TARGET DESCRIPTION: SATELLITE RHEA ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 1 | TARGET POSITION LEVEL 2 | STD=SATURN | STD=RHEA | ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 3 | WINDOWS | | ------------------------------------------------------------------------------------------------------------------------------------ DATA | COMMENTS | V = 9.7 | USE FOR ACQUISITION FOR TARGET 1 AND B-V = 0.78 | 2, BY OFFSETING FROM RHEA | ------------------------------------------------------------------------------------------------------------------------------------ 6755( 21) - 08/20/96 10:47 - [ 4] Visit: 01 Visit Requirements: ORIENT 75D TO 95D SCHED 100% BETWEEN 06-Sep-1996 AND 31-Oct-1996 On Hold Comments: Additional 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 Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 RHEA-OFFSET FOS/RD ACQ/PEA 4.3 G270H SEARCH-SIZE-X=1,SEARCH-SIZE-Y=3, 1 10 S ONBOARD ACQ FOR 2-3 K SCAN-STEP-Y=1.23 Comments: ACQUIRE RHEA AND OFFSET TO TORUS POSITION ------------------------------------------------------------------------------------------------------------------------------------ 2 RHEA-OFFSET FOS/RD ACQ/PEA 1.0 G270H SEARCH-SIZE-X=6,SEARCH-SIZE-Y=2, 1 10 S ONBOARD ACQ FOR 3-4 K SCAN-STEP-X=.61,SCAN-STEP-Y=.61 Comments: ACQUIRE RHEA AND OFFSET TO TORUS POSITION ------------------------------------------------------------------------------------------------------------------------------------ 3 SATURN-TORU FOS/RD IMAGE 4.3 G270H 3085 SUB-STEP=4,COMB=YES,Y-SPACE=256, 1 96 M S Y-SIZE=3 ------------------------------------------------------------------------------------------------------------------------------------ 4 SATURN-TORU FOS/RD IMAGE 4.3 G270H SUB-STEP=4,COMB=YES,Y-OFFSET=-128 1 9010 S S-HEIGHT ,Y-SPACE=256,Y-SIZE=2 Comments: Diodes should be mapped along bottom 1/3 and central 1/3 of aperture ------------------------------------------------------------------------------------------------------------------------------------ 6755( 21) - 08/20/96 10:47 - [ 5] Visit: 02 Visit Requirements: ORIENT 70D TO 95D SCHED 100% BETWEEN 06-Sep-1996 AND 31-Oct-1996 GUID TOL 2.1" On Hold Comments: Additional Comments: ORIENT is used to align FOS X-axis in orbital plane of satellites. FOS Y- axis should be along Saturn's spin axis Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 5 TETHYS FOS/RD ACQ/PEA 4.3 G270H SEARCH-SIZE-X=1,SEARCH-SIZE-Y=3, 1 1 S ONBOARD ACQ FOR 6 K SCAN-STEP-Y=1.23 Comments: ACQUIRE TETHYS AND OFFSET TO TORUS POSITION FOR OBSERVATION OF SATURN-RINGS-TORUS ------------------------------------------------------------------------------------------------------------------------------------ 6 TETHYS FOS/RD ACQ/PEA 1.0 G270H SEARCH-SIZE-X=6,SEARCH-SIZE-Y=2, 1 1 S ONBOARD ACQ FOR 8 K SCAN-STEP-X=0.61,SCAN-STEP-Y=0.61 Comments: ACQUIRE TETHYS ------------------------------------------------------------------------------------------------------------------------------------ 8 TETHYS FOS/RD ACQ/PEA 0.3 G270H SEARCH-SIZE-X=5,SEARCH-SIZE-Y=5, 1 1 S ONBOARD ACQ FOR 9 K SCAN-STEP-X=0.172, SCAN-STEP-Y=0.172 Comments: ACQUIRE TETHYS ------------------------------------------------------------------------------------------------------------------------------------ 9 TETHYS FOS/RD ACQ/PEA 2.0-BAR G270H SEARCH-SIZE-X=1,SEARCH-SIZE-Y=11, 1 1 S ONBOARD ACQ FOR 10-12 SEQ K SCAN-STEP-X=0,SCAN-STEP-Y=0.052, 9-10 NON-INT TYPE=DOWN Comments: ACQUIRE TETHYS ------------------------------------------------------------------------------------------------------------------------------------ 10 TETHYS FOS/RD ACCUM 2.0-BAR G270H 3085 1 24 M Comments: TETHYS SHOULD BE TRAVERSING DUSK ANSA. TETHYS SHOULD BE OCCULTED BY BAR ------------------------------------------------------------------------------------------------------------------------------------ 11 TETHYS FOS/RD ACCUM 2.0-BAR G270H 3085 1 100 M Comments: TETHYS SHOULD BE TRAVERSING DUSK ANSA. TETHYS SHOULD BE OCCULTED BY BAR ------------------------------------------------------------------------------------------------------------------------------------ 12 SATURN-RING FOS/RD IMAGE 4.3 G270H 3085 COMB=YES,SUB-STEP=4,Y-SPACE=256, 1 100 M EXPAND S-TORUS Y-SIZE=3 Comments: OFFSET TO TORUS POSITION FOR OBSERVATION OF SATURN-RINGS-TORUS ------------------------------------------------------------------------------------------------------------------------------------ 6755( 21) - 08/20/96 10:47 - [ 6] Visit: 03 Visit Requirements: ORIENT 75D TO 95D SCHED 100% BETWEEN 06-Sep-1996 AND 31-Oct-1996 On Hold Comments: Additional Comments: This visit to fill out 17th orbit. Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 9 TETHYS FOS/RD ACQ/PEA 4.3 G270H SEARCH-SIZE-X=1,SEARCH-SIZE-Y=3, 1 1 S ONBOARD ACQ FOR 10 K SCAN-STEP-Y=1.23 ------------------------------------------------------------------------------------------------------------------------------------ 10 TETHYS FOS/RD ACQ/PEA 1.0 G270H SEARCH-SIZE-X=6,SEARCH-SIZE-Y=2, 1 1 S ONBOARD ACQ FOR 11 K SCAN-STEP-X=0.61,SCAN-STEP-Y=0.61 ------------------------------------------------------------------------------------------------------------------------------------ 11 TETHYS FOS/RD ACCUM 1.0-PAI G270H 3085 1 10 M NO SPLIT MAX DUR 100% R-A Comments: TETHYS SHOULD BE TRAVERSING DUSK ANSA. THE DIODES SHOULD BE DEFLECTED SO THAT THEY ARE DIRECTLY UNDER THE 1.0-PAIR-A APERTURE ------------------------------------------------------------------------------------------------------------------------------------ 6755( 21) - 08/20/96 10:47 - [ 7] Summary Form for Proposal 6755 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations FOS/RD ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ/PEAK IMAGE ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters SEARCH-SIZE-X=1 SEARCH-SIZE-Y=3 SCAN-STEP-Y=1.23 SCAN-STEP-Y=.61 Y-SIZE=3 Y-SIZE=2 SCAN-STEP-Y=0.61 SCAN-STEP-Y=0.172 TYPE=DOWN Y-SPACE=256 SCAN-STEP-X=0.61 ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category SOLAR SYSTEM ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements ORIENT 75D TO 95D SCHED 100% BETWEEN 06-Sep-1996 AND 31-Oct-1996 ONBOARD ACQ FOR 2-3 ONBOARD ACQ FOR 3-4 ORIENT 70D TO 95D SCHED 100% BETWEEN 06-Sep-1996 AND 31-Oct-1996 GUID TOL 2.1" ONBOARD ACQ FOR 6 ONBOARD ACQ FOR 8 ONBOARD ACQ FOR 9 ONBOARD ACQ FOR 10-12 SEQ 9-10 NON-INT EXPAND ONBOARD ACQ FOR 10 ONBOARD ACQ FOR 11 NO SPLIT MAX DUR 100% ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements G270H ------------------------------------------------------------------------------------------------------------------------------------ Target Names RHEA-OFFSET SATURN-TORUS SATURN-TORUS-HEIGHT TETHYS SATURN-RINGS-TORUS ------------------------------------------------------------------------------------------------------------------------------------