7178( 4) - 03/06/98 11:12 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 7178 Version: 4 Check-in Date: 06-Mar-1998 11:07:05 1.Proposal Title: COMPOSITION OF THE SATURN BRIGHT RINGS ------------------------------------------------------------------------------------ 2. Proposal For 3. Cycle GTO/NIC 7 ------------------------------------------------------------------------------------ 4. Investigators Contact? PI: BRADFORD A. SMITH INSTITUTE FOR ASTRONOMY CoI: ROLAND MEIER UNIVERSITY OF HAWAII N ------------------------------------------------------------------------------------ 5. Abstract Groundbased spectroscopy established a quarter of a century ago that there must be substances other than water ice in Saturn's bright rings, as indicated by their UV reflectivity, which does not match that of pure ice. Speculation has ranged from silicate to carbonaceous material, but there remains no near-infrared evidence for anything but water ice. High resolution images obtained by the Voyager spacecraft show distinct color differences among narrow ringlets within Saturn's B ring, suggesting heterogeneous composition within the ring. The Voyager images also revealed that Saturn's C ring has a color that is distinctly different from the average A and B ring colors. High resolution NICMOS images may reveal non-water-ice material within narrow regions of the B ring and characterize the near-infrared differences between the B and A rings and the C ring. Observations of the rings are made at both ansae in filters that are both within and outside the 2-micron water- ice absorption band. Additional filters are used to investigate the spectral properties of the ringlets at still longer wavelengths. ------------------------------------------------------------------------------------ 7178( 4) - 03/06/98 11:12 - [ 2] Observations Description ------------------------ Camera 2 is first centered on the ring axis at the mid-radius of the bright ring system on the east side, then at the same equivalent location on the west side, and finally at a point just beyond the orbit of Rhea. Observations in the bright ring system are made with the F180M, F205M, F222M and F237M filters. The first pair examines the narrow ringlets of all bright rings both in and out of the water-ice absorption bands. The second pair extends coverage further into the infrared. The region beyond the orbit of Rhea is used for sky background. Real Time Justification ----------------------- None Calibration Justification ------------------------- Backgrounds are needed for long wavelength filters. Additional Comments ------------------- The visit requirements keep the observations with one month of Saturn opposition and orient Camera two such that one of its principal axes is aligned with the ring axis. ------------------------------------------------------------------------------------ Data Distribution Media: DAT Blocking Factor: 10 Ship To: Rodger I. Thompson, University of Arizona, Steward Obs./NICMOS, 933 N. Cherry Ave, Tucson, AZ 85721-0065 Ship Via: Email: thompson@as.arizona.edu ------------------------------------------------------------------------------------ 7178( 4) - 03/06/98 11:12 - [ 3] TARGET LIST b)Solar System Targets ------------------------------------------------------------------------------------------------------------------------------------ TARGET NUMBER: 1 | TARGET NAME: SATURN-RINGS-E ------------------------------------------------------------------------------------------------------------------------------------ TARGET DESCRIPTION: RING SATURN ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 1 | TARGET POSITION LEVEL 2 | STD=SATURN | TYPE=TORUS,LONG=270,LAT=0,RAD=105650,POL | E_LAT=+90 | ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 3 | WINDOWS | | ------------------------------------------------------------------------------------------------------------------------------------ DATA | COMMENTS | SURF(H) = +4.3+/-0.2 | Centered in the middle of the bright | ring system | ------------------------------------------------------------------------------------------------------------------------------------ TARGET NUMBER: 2 | TARGET NAME: SATURN-RINGS-W ------------------------------------------------------------------------------------------------------------------------------------ TARGET DESCRIPTION: RING SATURN ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 1 | TARGET POSITION LEVEL 2 | STD=SATURN | TYPE=TORUS,LONG=90,LAT=0,RAD=105650,POLE | _LAT=+90 | ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 3 | WINDOWS | | ------------------------------------------------------------------------------------------------------------------------------------ DATA | COMMENTS | SURF(H) = +4.3+/-0.2 | Centered in the middle of the bright | ring system | ------------------------------------------------------------------------------------------------------------------------------------ 7178( 4) - 03/06/98 11:12 - [ 4] TARGET LIST b)Solar System Targets ------------------------------------------------------------------------------------------------------------------------------------ TARGET NUMBER: 3 | TARGET NAME: BACKGROUND ------------------------------------------------------------------------------------------------------------------------------------ TARGET DESCRIPTION: RING SATURN ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 1 | TARGET POSITION LEVEL 2 | STD=SATURN | TYPE=TORUS,LONG=90,LAT=0,RAD=560000,POLE | _LAT=+90 | ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 3 | WINDOWS | | ------------------------------------------------------------------------------------------------------------------------------------ DATA | COMMENTS | SURF-BKG(V) = 20+/-0.2 | Puts the NIC2 FOV just clear of | Rhea's orbit. | ------------------------------------------------------------------------------------------------------------------------------------ 7178( 4) - 03/06/98 11:12 - [ 5] Visit: 01 Visit Priority: Visit Requirements: BETWEEN 24-Sep-1998 AND 24-Nov-1998 SCHED 100% ORIENT 41D TO 51D On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 SATURN-RING NIC2 MULTIAC NIC2-FI F180M 1.80000 SAMP-SEQ=STEP32,NSAMP=4 12 DEF GS ACQ SCENARIO SINGLE S-E CUM X ------------------------------------------------------------------------------------------------------------------------------------ 2 SATURN-RING NIC2 MULTIAC NIC2-FI F204M 2.04000 SAMP-SEQ=STEP32,NSAMP=4 12 DEF S-E CUM X ------------------------------------------------------------------------------------------------------------------------------------ 3 SATURN-RING NIC2 MULTIAC NIC2-FI F222M 2.22000 SAMP-SEQ=STEP32,NSAMP=4 12 DEF S-E CUM X ------------------------------------------------------------------------------------------------------------------------------------ 4 SATURN-RING NIC2 MULTIAC NIC2-FI F237M 2.37000 SAMP-SEQ=STEP32,NSAMP=4 12 DEF S-E CUM X ------------------------------------------------------------------------------------------------------------------------------------ 5 SATURN-RING NIC2 MULTIAC NIC2-FI F180M 1.80000 SAMP-SEQ=STEP32,NSAMP=4 12 DEF GS ACQ SCENARIO SINGLE S-W CUM X ------------------------------------------------------------------------------------------------------------------------------------ 6 SATURN-RING NIC2 MULTIAC NIC2-FI F204M 2.04000 SAMP-SEQ=STEP32,NSAMP=4 12 DEF S-W CUM X ------------------------------------------------------------------------------------------------------------------------------------ 7 SATURN-RING NIC2 MULTIAC NIC2-FI F222M 2.22000 SAMP-SEQ=STEP32,NSAMP=4 12 DEF S-W CUM X ------------------------------------------------------------------------------------------------------------------------------------ 8 SATURN-RING NIC2 MULTIAC NIC2-FI F237M 2.37000 SAMP-SEQ=STEP32,NSAMP=4 12 DEF S-W CUM X ------------------------------------------------------------------------------------------------------------------------------------ 9 BACKGROUND NIC2 MULTIAC NIC2 F180M 1.80000 SAMP-SEQ=STEP32,NSAMP=4 12 DEF CUM ------------------------------------------------------------------------------------------------------------------------------------ 10 BACKGROUND NIC2 MULTIAC NIC2 F204M 2.04000 SAMP-SEQ=STEP32,NSAMP=4 12 DEF CUM ------------------------------------------------------------------------------------------------------------------------------------ 11 BACKGROUND NIC2 MULTIAC NIC2 F222M 2.22000 SAMP-SEQ=STEP32,NSAMP=4 12 DEF CUM ------------------------------------------------------------------------------------------------------------------------------------ 12 BACKGROUND NIC2 MULTIAC NIC2 F237M 2.37000 SAMP-SEQ=STEP32,NSAMP=4 12 DEF CUM ------------------------------------------------------------------------------------------------------------------------------------ 7178( 4) - 03/06/98 11:12 - [ 6] Summary Form for Proposal 7178 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations NIC2 ------------------------------------------------------------------------------------------------------------------------------------ Opmodes MULTIACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters SAMP-SEQ=STEP32 NSAMP=4 ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GTO/NIC ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements BETWEEN 24-Sep-1998 AND 24-Nov-1998 SCHED 100% ORIENT 41D TO 51D GS ACQ SCENARIO SINGLE ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F180M F204M F222M F237M ------------------------------------------------------------------------------------------------------------------------------------ Target Names SATURN-RINGS-E SATURN-RINGS-W BACKGROUND ------------------------------------------------------------------------------------------------------------------------------------