! file: 5782 ! SCCSid: @(#)5782 1.5 4/5/95 Proposal_Information Title: SATURN RING-PLANE CROSSING, MAY 1995 Proposal_Category: GTO/HSP Scientific_Category: Solar System Cycle: 5 Investigators PI_name: Bosh, Amanda PI_Institution: Lowell Obs. Abstract: In 1995-1996, the Earth and the Sun will pass through Saturn's ring plane. The Earth will pass through 3 times (22 May 1995, 10 August 1995, 11 Feb 1996), and the Sun will pass through once (19 November 1995). All but the 11 Feb 1996 event will be visible from HST. During the crossings of the Earth through Saturn's ring plane, the rings will become very thin and dark. By monitoring the brightness of the rings as they become very thin, we will be able to determine the time of ring-plane crossing and the residual brightness of the rings at this time. The time of the ring- plane crossing will place additional constraints on the precession rate of Saturn's pole. The recent occultations by Saturn's rings have produced a measurement of this value, but it is not known very well (French et al., 1993; Bosh, 1994; Elliot et al., 1993). A measure of the brightness of the rings in their edge-on configuration, combined with photometric properties of the rings derived from early calibration observations will allow us to determine the thickness of the rings. Questions Observing_Description: We will monitor the brightness of Saturn's rings as the Earth passes through Saturn's ring plane. This set of observations covers the first of the crossings of the Earth through Saturn's ring-plane for the 1995-1996 events. We will obtain a series of WFPC2 images at 8900 A (in methane band, to reduce scattered light from Saturn) of Saturn and its rings for 7 orbits centered on the predicted time of ring-plane crossing. Imaging for 7 orbits allows for uncertainty in the precession of Saturn's ring-plane pole. Each orbit will consist of a set of 2 short exposures (for satellite photometric calibration) and as many 400-sec exposures as will fit in the rest of the orbit (to detect residual flux from vertical face of rings). An additional orbit before or after the event (preferably after) will obtain additional calibration data. Real_Time_Justification: Calibration_Justification: Additional_Comments : Time critical long observation. Will be near Moon. Will need to ignore SAA to greatest extent possible (including dropping to gyro control if necessary). May have to use guidestar handoff. Edited 4/21 to replace POS TARGs with SSTL offsets, and use CH4 filter "apertures". (ADS) Fixed_Targets Solar_System_Targets Target_Number: 1 Target_Name: SATURN Description: PLANET SATURN LEVEL_1: STD=SATURN level_2: TYPE=POS_ANGLE, RAD=16.3, ANG=49, REF=SUN WINDOW: WND1= 20-MAY-1995 TO 25-MAY-1995 Flux: SURF(V) = 7.0 +/- 0.1 B-V = 1.0 +/- 0.1 Comments: Planet center, for WF obs. Target_Number: 2 Target_Name: SATURN-PC Description: RING SATURN LEVEL_1: STD=SATURN level_2: TYPE=POS_ANGLE, RAD=14.1, ANG=38, REF=SUN WINDOW: WND1= 20-MAY-1995 TO 25-MAY-1995 Flux: SURF(V) = 15.0 +/- 0.5 Comments: West ansa of outer main ring. Target_Number: 3 Target_Name: SATURN-WEST-ERING Description: RING SATURN Level_1: STD = SATURN ! Satellite of Sun Level_2: TYPE = TORUS, ! Satellite of Level_1 LONG = 90, LAT = 0, RAD = 3.25E05, POLE_LAT = +90, POLE_LONG = 0 Window: Flux: SURF(V) = 18.6 ! Include at least V and B-V Comments: Western ansa of Saturn E ring centered 50 arcsec from center of Saturn. Generic_Targets Scan_Data Visits Visit_Number: 1 Visit_Requirements: BETWEEN 21-MAY-95:23:40 AND 22-MAY-95:01:16 ORIENT -24D TO 24D FROM NOMINAL On_Hold_Comments: ! ORBIT 1 Exposure_number: 10 Target_Name: SATURN Config: WFPC2 Opmode: IMAGE Aperture: FQCH4W3 Sp_Element: FQCH4N Wavelength: 8922 Optional_Parameters: CR-SPLIT=NO, CLOCKS=YES, ATD-GAIN=7 Number_of_iterations:2 Time_Per_Exposure: 7S Special_Requirements:SEQ 10-20 NON-INT NO SPLIT Comments: IGNORE SAA, short exposure for satellite photometry Exposure_number: 20 Target_Name: SATURN Config: WFPC2 Opmode: IMAGE Aperture: FQCH4W3 Sp_Element: FQCH4N Wavelength: 8922 Optional_Parameters: CR-SPLIT=NO, CLOCKS=YES, ATD-GAIN=7 Number_of_iterations:3 Time_Per_Exposure: 400S Special_Requirements:SAME POS AS 10 Comments: CH4 EXPOSURES FULL ACQ, IGNORE SAA ! ORBIT 2 Exposure_number: 40 Target_Name: SATURN Config: WFPC2 Opmode: IMAGE Aperture: FQCH4W3 Sp_Element: FQCH4N Wavelength: 8922 Optional_Parameters: CR-SPLIT=NO, CLOCKS=YES, ATD-GAIN=7 Number_of_iterations:2 Time_Per_Exposure: 7S Special_Requirements:SEQ 40-50 NON-INT NO SPLIT Comments: IGNORE SAA, short exposures for satellite photometry Exposure_number: 50 Target_Name: SATURN Config: WFPC2 Opmode: IMAGE Aperture: FQCH4W3 Sp_Element: FQCH4N Wavelength: 8922 Optional_Parameters: CR-SPLIT=NO, CLOCKS=YES, ATD-GAIN=7 Number_of_iterations:4 Time_Per_Exposure: 400S Special_Requirements:SAME POS AS 40 Comments: CH4 EXPOSURES REACQ, IGNORE SAA ! ORBIT 3 Exposure_number: 70 Target_Name: SATURN Config: WFPC2 Opmode: IMAGE Aperture: FQCH4W3 Sp_Element: FQCH4N Wavelength: 8922 Optional_Parameters: CR-SPLIT=NO, CLOCKS=YES, ATD-GAIN=7 Number_of_iterations:2 Time_Per_Exposure: 7S Special_Requirements:SEQ 70-80 NON-INT NO SPLIT Comments: IGNORE SAA, short exposures for satellite photometry Exposure_number: 80 Target_Name: SATURN Config: WFPC2 Opmode: IMAGE Aperture: FQCH4W3 Sp_Element: FQCH4N Wavelength: 8922 Optional_Parameters: CR-SPLIT=NO, CLOCKS=YES, ATD-GAIN=7 Number_of_iterations:4 Time_Per_Exposure: 400S Special_Requirements:SAME POS AS 70 Comments: CH4 EXPOSURES REACQ, IGNORE SAA ! ORBIT 4 Exposure_number: 100 Target_Name: SATURN Config: WFPC2 Opmode: IMAGE Aperture: FQCH4W3 Sp_Element: FQCH4N Wavelength: 8922 Optional_Parameters: CR-SPLIT=NO, CLOCKS=YES, ATD-GAIN=7 Number_of_iterations:2 Time_Per_Exposure: 7S Special_Requirements:SEQ 100-110 NON-INT NO SPLIT Comments: IGNORE SAA, short exposures for satellite photometry Exposure_number: 110 Target_Name: SATURN Config: WFPC2 Opmode: IMAGE Aperture: FQCH4W3 Sp_Element: FQCH4N Wavelength: 8922 Optional_Parameters: CR-SPLIT=NO, CLOCKS=YES, ATD-GAIN=7 Number_of_iterations:4 Time_Per_Exposure: 400S Special_Requirements:SAME POS AS 100 Comments: CH4 EXPOSURES REACQ, IGNORE SAA ! ORBIT 5 Exposure_number: 130 Target_Name: SATURN Config: WFPC2 Opmode: IMAGE Aperture: FQCH4W3 Sp_Element: FQCH4N Wavelength: 8922 Optional_Parameters: CR-SPLIT=NO, CLOCKS=YES, ATD-GAIN=7 Number_of_iterations:2 Time_Per_Exposure: 7S Special_Requirements:SEQ 130-140 NON-INT NO SPLIT Comments: IGNORE SAA, short exposures for satellite photometry Exposure_number: 140 Target_Name: SATURN Config: WFPC2 Opmode: IMAGE Aperture: FQCH4W3 Sp_Element: FQCH4N Wavelength: 8922 Optional_Parameters: CR-SPLIT=NO, CLOCKS=YES, ATD-GAIN=7 Number_of_iterations:4 Time_Per_Exposure: 400S Special_Requirements:SAME POS AS 130 Comments: CH4 EXPOSURES REACQ, IGNORE SAA ! ORBIT 6 Exposure_number: 160 Target_Name: SATURN Config: WFPC2 Opmode: IMAGE Aperture: FQCH4W3 Sp_Element: FQCH4N Wavelength: 8922 Optional_Parameters: CR-SPLIT=NO, CLOCKS=YES, ATD-GAIN=7 Number_of_iterations:2 Time_Per_Exposure: 7S Special_Requirements:SEQ 160-170 NON-INT NO SPLIT Comments: IGNORE SAA, short exposures for satellite photometry Exposure_number: 170 Target_Name: SATURN Config: WFPC2 Opmode: IMAGE Aperture: FQCH4W3 Sp_Element: FQCH4N Wavelength: 8922 Optional_Parameters: CR-SPLIT=NO, CLOCKS=YES, ATD-GAIN=7 Number_of_iterations:4 Time_Per_Exposure: 400S Special_Requirements:SAME POS AS 160 Comments: CH4 EXPOSURES REACQ, IGNORE SAA ! ORBIT 7 Exposure_number: 190 Target_Name: SATURN Config: WFPC2 Opmode: IMAGE Aperture: FQCH4W3 Sp_Element: FQCH4N Wavelength: 8922 Optional_Parameters: CR-SPLIT=NO, CLOCKS=YES, ATD-GAIN=7 Number_of_iterations:2 Time_Per_Exposure: 7S Special_Requirements:SEQ 190-200 NON-INT NO SPLIT Comments: IGNORE SAA, short exposures for satellite photometry Exposure_number: 200 Target_Name: SATURN Config: WFPC2 Opmode: IMAGE Aperture: FQCH4W3 Sp_Element: FQCH4N Wavelength: 8922 Optional_Parameters: CR-SPLIT=NO, CLOCKS=YES, ATD-GAIN=7 Number_of_iterations:4 Time_Per_Exposure: 400S Special_Requirements:SAME POS AS 190 Comments: CH4 EXPOSURES REACQ, IGNORE SAA Visit_Number: 2 Visit_Requirements: SEQ 1-2 WITHIN 24H ORIENT -24D TO 24D FROM NOMINAL On_Hold_Comments: Exposure_number: 220 Target_Name: SATURN-PC Config: WFPC2 Opmode: IMAGE Aperture: PC1-FIX Sp_Element: FQCH4P15 Wavelength: 8922 Optional_Parameters: CR-SPLIT=NO Number_of_iterations:3 Time_Per_Exposure: 100S ! Special_Requirements:POS TARG 0, 0 Comments: test exposure for Nicholson Exposure_number: 230 Target_Name: SATURN Config: WFPC2 Opmode: IMAGE Aperture: FQCH4W3 Sp_Element: FQCH4N Wavelength: 8922 Optional_Parameters: CR-SPLIT=NO, CLOCKS=YES, ATD-GAIN=7 Number_of_iterations:3 Time_Per_Exposure: 60S Special_Requirements: Comments: Exposure_Number: 240 ! Section 6.5 Target_Name: SATURN-WEST-ERING Config: WFPC2 Opmode: IMAGE Aperture: WF2-FIX ! Section 9 Sp_Element: F675W ! Section 9 Wavelength: 6714 Optional_Parameters: CR-SPLIT=NO,SUM=2X2 ! Section 9 Number_of_Iterations:1 Time_Per_Exposure: 400S Special_Requirements:POS TARG 16.8, -9.0 ! Section 7.2 NO SPLIT Comments: Test exposure for Nicholson Data_Distribution Medium: 8MM Blocking_Factor: 10 Ship_To: PI_Address Ship_Via: UPS