! Hubble Space Telescope Cycle 5 (1995) Phase II Proposal Template ! $Id: 5830,v 2.1 1995/07/28 18:11:28 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: festou-781.prop ! Date generated: Fri Dec 16 14:48:28 EST 1994 ! Proposal_Information ! Section 4 Title: THE SMALL ICY PARTICLES OF THE A AND B RINGS OF SATURN Proposal_Category: GO Scientific_Category: Solar System Cycle: 5 Investigators PI_name: Michel C. FESTOU PI_Institution: Observatoire Midi-Pyrenees CoI_Name: S. Alan STERN CoI_Institution: Southwest Research Institute, San Antonio Contact: N ! Y or N (designate at most one contact) CoI_Name: Don E. Shemansky CoI_Institution: Univ. of Southern Calif., L.A. Contact: N ! Y or N (designate at most one contact) Abstract: ! Free format text (please update) Near 1650 Angstrom, a strong absorption attributed to small water ice particles, and possibly water vapor, has been seen in Voyager and IUE spectra of the two main rings of Saturn. These small particles are not seen at longer wavelengths, even in forward scattering, except in the form of spokes, because of the masking effects of the dominant large particles. All the fainter rings, however, show that small particles are produced in large amounts, and thus indicate that they should be present in every ring. No constraining observations exist that allow a description of the production of icy grains and water molecules in the Saturn rings, and to evaluate the effects of their transport and subsequent destruction in OH radicals and H atoms. GHRS FUV spectra of the A and B rings, to be obtained at or near the time of the 1995-96 ring crossing, will allow us to distinguish the properties of solid state vs gaseous absorbers. When the opening angle of the rings will be small, the front side of the rings will occult the far side of the same rings and will permit a complete characterization of the cloud of water that surrounds the icy blocks. Later, when the rings opening angle will be larger, only the solid particles will absorb and their properties will be derived. All these observations, address the important question of the role of the source of H atoms and OH radicals inside the Saturnian system, with important consequences for the planning of the observing sequences of some of the CASSINI instruments. Questions ! Free format text (please update) Observing_Description: Offset acq. of Rhea, then GHRS spectra of the near and far edges of the Saturnian rings. Do once in Oct. and then in May (when rings are more open). Real_Time_Justification: Calibration_Justification: ! Move appropriate text from Real_Time_Justification Additional_Comments: Solar_System_Targets ! Section 5.2 Target_Number:1 Target_Name:Rhea Description:satellite Rhea Level_1:STD=SATURN ! Satellite of Sun Level_2:STD=RHEA ! Satellite of Saturn Level_3: ! Satellite of Level_2 Window:OLG OF RHEA FROM EARTH Between 200 340 Flux:V=12.9 B-V=0.67 Comments:ACQ TARGET. OLG CONSTRAINTS APPROXIMATE. Target_Number:2 Target_Name:FARSIDE Description:RING SATURN Level_1:STD=SATURN ! Satellite of Sun Level_2:TYPE=TORUS,LONG=153,LAT=0,RAD=1.9E5,POLE_LAT=90 Level_3: ! Satellite of Level_2 Window: Flux:V=12.9 B-V=0.67 Comments:EDGE OF RING ON FAR SIDE OF SATURN, TOWARDS WEST. Mean radius of rings taken as 190,000 km, a near limb observation at 1 arcsec from that limb corresponds to degrees a value of 156. With 153 degrees, the line of sight passes at 2.23 arc sec from the limb. Target_Number:3 Target_Name:NEARSIDE Description:RING SATURN Level_1:STD=SATURN ! Satellite of Sun Level_2:TYPE=TORUS,LONG=27,LAT=0,RAD=1.9E5,POLE_LAT=90 Level_3: ! Satellite of Level_2 Window: Flux:V=12.9 B-V=0.67 Comments:EDGE OF RING ON NEAR SIDE OF SATURN, TOWARDS WEST. See above. ! This is a template for a single visit containing a single exposure ! Repeat exposure and visit blocks as needed Visits ! Section 6 Visit_Number: 1 Visit_Requirements: BETWEEN 01-OCT-1995 AND 20-OCT-1995 On_Hold_Comments: Visit_Comments: BEST IF ORIENTED SO THAT RINGS ALIGN WITH GHRS X AXIS Exposure_Number: 10 ! Section 6.5 Target_Name: RHEA Config: HRS Opmode: ACQ Aperture: 2.0 Sp_Element: MIRROR-N2 Wavelength: Optional_Parameters: BRIGHT=RETURN, LOCATE=EXTENDED Number_of_Iterations: 1 Time_Per_Exposure: 18S Special_Requirements: ONBOARD ACQ FOR 20-35 ! Uncomment or copy exposure level special requirements needed ! INTeractive ACQuisition FOR ! ONBOARD ACQuisition FOR ! POSition TARGet , ! SAME POSition AS ! DO FOR TARGets ! FGS only ! PARallel WITH ! GROUP-FGS WITHIN