7321( 7) - 10/02/97 16:50 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 7321 Version: 7 Check-in Date: 02-Oct-1997 16:48:27 1.Proposal Title: Spatially resolved multispectral investigation of Titan's troposphere and stratosphere ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Cycle SOLAR SYSTEM GO 7 ------------------------------------------------------------------------------------ 5. Investigators Contact? PI: MARK T. LEMMON UNIVERSITY ARIZONA CoI: Peter Smith Lunar and Planetary Laboratory N CoI: Ralph Lorenz Lunar and Planetary Laboratory N CoI: Robert West Jet Propulsion Laboratory N ------------------------------------------------------------------------------------ 6. Abstract Saturn's moon Titan has a thick, hazy atmosphere obscuring a surface that has only recently been observed in the near- infrared. Despite observations of surface albedo features, the nature of the surface remains hidden due to our imprecise knowledge of the atmosphere. All existing radiative transfer models of Titan's atmosphere (which are used to calculate surface albedos) are driven primarily by Titan's spectral geometric albedo, which is not spatially resolved. The models describe an atmosphere that does not exist: strong north- south variations that vary with wavelength from +18\ global average; Titan is highly limb darkened at a few wavelengths, limb brightened at others, and has not been observed with spatial resolution at most wavelengths; the brightness of the atmosphere is a non-linear effect of the physical parameters, so a model of the average brightness is not an average model. We propose to obtain spatially and spectrally resolved observations of Titan sufficient to constrain the photometric and polarimetric properties of the atmosphere, and to use the information to generate a new, spatially resolved model of the atmosphere. The model will be used to interpret existing albedo maps of Titan, existing observations of clouds in Titan's troposphere, and existing and simultaneous observations of Titan's near-infrared light curve. This procedure will constrain the nature and composition of surface materials and help prepare for Cassini observations and Huygens in situ measurements. ------------------------------------------------------------------------------------ 7321( 7) - 10/02/97 16:50 - [ 2] Observations Description ------------------------ WFPC2 orbits Using exposure times and gains that have proven sufficient in previous cycles, we can complete our WFPC2 program in one orbit. A 52-minute orbit has 9 minutes for acquisition, 8 minutes for science exposures, and 35 minutes of overhead for 7 CRSPLIT images. S/N will be near 100 for the F336W and FQCH4N-D images and near 200 for the others. STIS orbits Each orbit is identical in exposures, and will see different parts of Titan. With each grating, we will observe an approximately north-south scan through Titan's center, followed by identical observations approximately 0.125 and 0.25arcsec away from the center. The central wavelength for G750L will be approximately 7715Angstrom and only one central wavelength will be used. We will use 9 minutes for guide star acquisition, 7.5 minutes for target acquisition (checkbox=9, geometric method, using approximately 1-sec exposures of the F28X50LP filter), 16 minutes for exposure overhead (3 CRSPLIT=2 observations with one spectral element followed by 3 CRSPLIT=2 observations with the other), and 19.5 minutes for science exposures. The program is (scientifically) easiest to implement if the spatial axis of the slit is oriented parallel to north- south on Titan, but the offsets can be calculated for any other orientation (the acquisition plan will locate an area in Titan's northern hemisphere at the sub-Earth longitude). Acquisition peak up is not desired due to the spatial scan in the science observations. S/N will be about 150 for the brightest part of the disk for 4000Angstrom and 8900Angstrom based on the STIS exposure time calculator. NICMOS orbits Each orbit is identical in exposures, and will see different parts of Titan. We will use 9 minutes for acquisition; 55 seconds for one camera change from 1 to 2 (overhead based on NICMOS FAQ); 20 seconds per NIC1 filter (allowing 2 reads), 55 seconds per NIC2 filter (allowing 2 reads at each of two positions within several arcsec) for a total of 10 minutes; and 32 minutes for science exposures, S/N near 200 in the brightest part of each image using the NICMOS exposure time calculator. Real Time Justification ----------------------- Time-critical: For STIS and NICMOS, the two orbits should look at different parts of Titan to allow photometric models of different surface components and to ensure that we can separate the effects of the surface and transient clouds. One major terrain is visible for 4 out of every 16 days, the other is visible for 12 out of every 16 days. It is helpful, but not required, if the whole project is completed within two weeks. It is preferred that the STIS slit be approximately aligned with Titan's north-south axis, but the program may be carried out with any orientation if the orientation is known in advance (for planning the required offsets). We will obtain 10-15 nights of ground based near infrared spectroscopy with University of Arizona Observatories facilities. These will be used to obtain a light curve of Titan at the time of the HST observations for comparison with past light curves. Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ 7321( 7) - 10/02/97 16:50 - [ 3] Data Distribution Media: 8MM Blocking Factor: 10 Ship To: PI_Address Ship Via: Email: ------------------------------------------------------------------------------------ 7321( 7) - 10/02/97 16:50 - [ 4] TARGET LIST b)Solar System Targets ------------------------------------------------------------------------------------------------------------------------------------ TARGET NUMBER: 1 | TARGET NAME: TITAN-LEADING ------------------------------------------------------------------------------------------------------------------------------------ TARGET DESCRIPTION: SATELLITE TITAN ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 1 | TARGET POSITION LEVEL 2 | STD=SATURN | STD=TITAN | ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 3 | WINDOWS | | CML OF TITAN FROM EARTH BETWEEN 80 140, | PHASE OF SATURN FROM EARTH BETWEEN -4 4 | ------------------------------------------------------------------------------------------------------------------------------------ DATA | COMMENTS | SURF(V) = 7.8+/-0.3 | observe bright feature located on SURF(B) = 9.2+/-0.3 | leading hemisphere of Titan SURF(4000)=6.0+/-0.6e-13 | SURF(5000)=2.3+/-0.2e-12 | SURF(8900)=5.0+/-0.5e-13 | SURF(9400)=2.0+/-0.2e-12 | SURF(20300)=2.2+/-0.2e-13 | SURF(21600)=3.1+/-0.3e-14 | | ------------------------------------------------------------------------------------------------------------------------------------ TARGET NUMBER: 2 | TARGET NAME: TITAN-TRAILING ------------------------------------------------------------------------------------------------------------------------------------ TARGET DESCRIPTION: SATELLITE TITAN ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 1 | TARGET POSITION LEVEL 2 | STD=SATURN | STD=TITAN | ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 3 | WINDOWS | | CML OF TITAN FROM EARTH BETWEEN 180 20, | PHASE OF SATURN FROM EARTH BETWEEN -4 4 | ------------------------------------------------------------------------------------------------------------------------------------ DATA | COMMENTS | SURF(V) = 7.8+/-0.3 | observe trailing hemisphere of Titan SURF(B) = 9.2+/-0.3 | SURF(4000)=6.0+/-0.6e-13 | SURF(5000)=2.3+/-0.2e-12 | SURF(8900)=5.0+/-0.5e-13 | SURF(9400)=2.0+/-0.2e-12 | SURF(20300)=2.2+/-0.2e-13 | SURF(21600)=3.1+/-0.3e-14 | | ------------------------------------------------------------------------------------------------------------------------------------ 7321( 7) - 10/02/97 16:50 - [ 5] TARGET LIST b)Solar System Targets ------------------------------------------------------------------------------------------------------------------------------------ TARGET NUMBER: 3 | TARGET NAME: TITAN ------------------------------------------------------------------------------------------------------------------------------------ TARGET DESCRIPTION: SATELLITE TITAN ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 1 | TARGET POSITION LEVEL 2 | STD=SATURN | STD=TITAN | ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 3 | WINDOWS | | PHASE OF SATURN FROM EARTH BETWEEN -4 4 | ------------------------------------------------------------------------------------------------------------------------------------ DATA | COMMENTS | SURF(V) = 7.8+/-0.3 | observe any part of Titan SURF(B) = 9.2+/-0.3 | SURF(4000)=6.0+/-0.6e-13 | SURF(5000)=2.3+/-0.2e-12 | SURF(8900)=5.0+/-0.5e-13 | SURF(9400)=2.0+/-0.2e-12 | SURF(20300)=2.2+/-0.2e-13 | SURF(21600)=3.1+/-0.3e-14 | | ------------------------------------------------------------------------------------------------------------------------------------ 7321( 7) - 10/02/97 16:50 - [ 6] Visit: 01 Visit Priority: Visit Requirements: ORIENT 25D TO 65D On Hold Comments: Additional Comments: This visit is intended to observe the area around a large bright feature on Titan with the STIS slit aligned north to south or south to north, so ORIENT 205D TO 245D is also acceptable Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 TITAN-LEADI NIC1 MULTIAC NIC1 F145M SAMP-SEQ=STEP8,NSAMP=9 2 DEF NG CUM ------------------------------------------------------------------------------------------------------------------------------------ 2 TITAN-LEADI NIC1 MULTIAC NIC1 F164N SAMP-SEQ=STEP8,NSAMP=23 2 DEF NG CUM ------------------------------------------------------------------------------------------------------------------------------------ 3 TITAN-LEADI NIC1 MULTIAC NIC1 POL0S SAMP-SEQ=STEP8,NSAMP=8 2 DEF NG CUM ------------------------------------------------------------------------------------------------------------------------------------ 4 TITAN-LEADI NIC1 MULTIAC NIC1 POL120S SAMP-SEQ=STEP8,NSAMP=8 2 DEF NG CUM ------------------------------------------------------------------------------------------------------------------------------------ 5 TITAN-LEADI NIC1 MULTIAC NIC1 POL240S SAMP-SEQ=STEP8,NSAMP=8 2 DEF NG CUM ------------------------------------------------------------------------------------------------------------------------------------ 6 TITAN-LEADI NIC2 MULTIAC NIC2 F187N SAMP-SEQ=STEP8,NSAMP=9, 1 DEF NG CUM PATTERN=ONE-CHOP,NUM-POS=2, CHOP-SIZE=5.0 ------------------------------------------------------------------------------------------------------------------------------------ 7 TITAN-LEADI NIC2 MULTIAC NIC2 F190N SAMP-SEQ=STEP8,NSAMP=9, 1 DEF NG CUM PATTERN=ONE-CHOP,NUM-POS=2, CHOP-SIZE=5.0 ------------------------------------------------------------------------------------------------------------------------------------ 8 TITAN-LEADI NIC2 MULTIAC NIC2 F207M SAMP-SEQ=STEP8,NSAMP=5, 1 DEF NG CUM PATTERN=ONE-CHOP,NUM-POS=2, CHOP-SIZE=5.0 ------------------------------------------------------------------------------------------------------------------------------------ 9 TITAN-LEADI NIC2 MULTIAC NIC2 F212N SAMP-SEQ=STEP8,NSAMP=9, 1 DEF NG CUM PATTERN=ONE-CHOP,NUM-POS=2, CHOP-SIZE=5.0 ------------------------------------------------------------------------------------------------------------------------------------ 10 TITAN-LEADI NIC2 MULTIAC NIC2 F215N SAMP-SEQ=STEP8,NSAMP=9, 1 DEF NG CUM PATTERN=ONE-CHOP,NUM-POS=2, CHOP-SIZE=5.0 ------------------------------------------------------------------------------------------------------------------------------------ 11 TITAN-LEADI NIC2 MULTIAC NIC2 F216N SAMP-SEQ=STEP8,NSAMP=9, 1 DEF NG CUM PATTERN=ONE-CHOP,NUM-POS=2, CHOP-SIZE=5.0 ------------------------------------------------------------------------------------------------------------------------------------ 12 TITAN-LEADI NIC2 MULTIAC NIC2 POL0L SAMP-SEQ=STEP8,NSAMP=6, 1 DEF NG CUM PATTERN=ONE-CHOP,NUM-POS=2, CHOP-SIZE=5.0 ------------------------------------------------------------------------------------------------------------------------------------ 7321( 7) - 10/02/97 16:50 - [ 7] Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 13 TITAN-LEADI NIC2 MULTIAC NIC2 POL120L SAMP-SEQ=STEP8,NSAMP=6, 1 DEF NG CUM PATTERN=ONE-CHOP,NUM-POS=2, CHOP-SIZE=5.0 ------------------------------------------------------------------------------------------------------------------------------------ 14 TITAN-LEADI NIC2 MULTIAC NIC2 POL240L SAMP-SEQ=STEP8,NSAMP=6, 1 DEF NG CUM PATTERN=ONE-CHOP,NUM-POS=2, CHOP-SIZE=5.0 ------------------------------------------------------------------------------------------------------------------------------------ 20 TITAN-LEADI STIS/C ACQ F28X50L MIRROR ACQTYPE=DIFFUSE, 1 0.5 S ONBOARD ACQ FOR 30,40 NG CD P DIFFUSE-CENTER=GEOMETRIC-CENTER, CHECKBOX=9 ------------------------------------------------------------------------------------------------------------------------------------ 30 TITAN-LEADI STIS/C ACCUM 52X0.1 G430L 4300 PATTERN=PERP-TO-SLIT,NUM-POS=3, 1 180 S NG CD STEP-SIZE=0.125, PATTERN-DIRECTION=PLUS,CR-SPLIT=2 ------------------------------------------------------------------------------------------------------------------------------------ 40 TITAN-LEADI STIS/C ACCUM 52X0.1 G750L 7751 PATTERN=PERP-TO-SLIT,NUM-POS=3, 1 100 S NG CD STEP-SIZE=0.125, PATTERN-DIRECTION=PLUS,CR-SPLIT=2 Comments: Contemporaneous flat field requested for this exposure ------------------------------------------------------------------------------------------------------------------------------------ 45 NONE STIS/C ACCUM 52X0.2 G750L 7751 LAMP=TUNGSTEN,GAIN=1,CR-SPLIT=2 1 60 S CD Comments: Contemporaneous flatfield ------------------------------------------------------------------------------------------------------------------------------------ 7321( 7) - 10/02/97 16:50 - [ 8] Visit: 02 Visit Priority: Visit Requirements: On Hold Comments: Additional Comments: It is preferable but not required to have this visit be close in time to either of the other visits Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 50 TITAN WFPC2 IMAGE PC1 F336W CR-SPLIT=0.5,ATD-GAIN=7 1 200 S ------------------------------------------------------------------------------------------------------------------------------------ 60 TITAN WFPC2 IMAGE PC1 F439W CR-SPLIT=0.5,ATD-GAIN=15 1 40 S ------------------------------------------------------------------------------------------------------------------------------------ 61 TITAN WFPC2 IMAGE PC1 F547M CR-SPLIT=1,ATD-GAIN=15 1 7 S ------------------------------------------------------------------------------------------------------------------------------------ 62 TITAN WFPC2 IMAGE PC1 F588N CR-SPLIT=0.5,ATD-GAIN=15 1 40 S ------------------------------------------------------------------------------------------------------------------------------------ 63 TITAN WFPC2 IMAGE PC1 F673N CR-SPLIT=0.5,ATD-GAIN=15 1 40 S ------------------------------------------------------------------------------------------------------------------------------------ 64 TITAN WFPC2 IMAGE FQCH4N1 FQCH4N15 6193 CR-SPLIT=0.5,ATD-GAIN=15 1 80 S 5 ------------------------------------------------------------------------------------------------------------------------------------ 65 TITAN WFPC2 IMAGE FQCH4P1 FQCH4P15 8929 CR-SPLIT=0.5,ATD-GAIN=7 1 200 S 5 ------------------------------------------------------------------------------------------------------------------------------------ 7321( 7) - 10/02/97 16:50 - [ 9] Visit: 03 Visit Priority: Visit Requirements: ORIENT 25D TO 65D On Hold Comments: Additional Comments: This visit is intended to observe the darker side of Titan with the slit aligned north-south, and ORIENT 205D TO 245D is acceptable Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 TITAN-TRAIL NIC1 MULTIAC NIC1 F145M SAMP-SEQ=STEP8,NSAMP=9 2 DEF ING CUM ------------------------------------------------------------------------------------------------------------------------------------ 2 TITAN-TRAIL NIC1 MULTIAC NIC1 F164N SAMP-SEQ=STEP8,NSAMP=23 2 DEF ING CUM ------------------------------------------------------------------------------------------------------------------------------------ 3 TITAN-TRAIL NIC1 MULTIAC NIC1 POL0S SAMP-SEQ=STEP8,NSAMP=8 2 DEF ING CUM ------------------------------------------------------------------------------------------------------------------------------------ 4 TITAN-TRAIL NIC1 MULTIAC NIC1 POL120S SAMP-SEQ=STEP8,NSAMP=8 2 DEF ING CUM ------------------------------------------------------------------------------------------------------------------------------------ 5 TITAN-TRAIL NIC1 MULTIAC NIC1 POL240S SAMP-SEQ=STEP8,NSAMP=8 2 DEF ING CUM ------------------------------------------------------------------------------------------------------------------------------------ 6 TITAN-TRAIL NIC2 MULTIAC NIC2 F187N SAMP-SEQ=STEP8,NSAMP=9, 1 DEF ING CUM PATTERN=ONE-CHOP,NUM-POS=2, CHOP-SIZE=5.0 ------------------------------------------------------------------------------------------------------------------------------------ 7 TITAN-TRAIL NIC2 MULTIAC NIC2 F190N SAMP-SEQ=STEP8,NSAMP=9, 1 DEF ING CUM PATTERN=ONE-CHOP,NUM-POS=2, CHOP-SIZE=5.0 ------------------------------------------------------------------------------------------------------------------------------------ 8 TITAN-TRAIL NIC2 MULTIAC NIC2 F207M SAMP-SEQ=STEP8,NSAMP=5, 1 DEF ING CUM PATTERN=ONE-CHOP,NUM-POS=2, CHOP-SIZE=5.0 ------------------------------------------------------------------------------------------------------------------------------------ 9 TITAN-TRAIL NIC2 MULTIAC NIC2 F212N SAMP-SEQ=STEP8,NSAMP=9, 1 DEF ING CUM PATTERN=ONE-CHOP,NUM-POS=2, CHOP-SIZE=5.0 ------------------------------------------------------------------------------------------------------------------------------------ 10 TITAN-TRAIL NIC2 MULTIAC NIC2 F215N SAMP-SEQ=STEP8,NSAMP=9, 1 DEF ING CUM PATTERN=ONE-CHOP,NUM-POS=2, CHOP-SIZE=5.0 ------------------------------------------------------------------------------------------------------------------------------------ 11 TITAN-TRAIL NIC2 MULTIAC NIC2 F216N SAMP-SEQ=STEP8,NSAMP=9, 1 DEF ING CUM PATTERN=ONE-CHOP,NUM-POS=2, CHOP-SIZE=5.0 ------------------------------------------------------------------------------------------------------------------------------------ 12 TITAN-TRAIL NIC2 MULTIAC NIC2 POL0L SAMP-SEQ=STEP8,NSAMP=6, 1 DEF ING CUM PATTERN=ONE-CHOP,NUM-POS=2, CHOP-SIZE=5.0 ------------------------------------------------------------------------------------------------------------------------------------ 7321( 7) - 10/02/97 16:50 - [ 10] Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 13 TITAN-TRAIL NIC2 MULTIAC NIC2 POL120L SAMP-SEQ=STEP8,NSAMP=6, 1 DEF ING CUM PATTERN=ONE-CHOP,NUM-POS=2, CHOP-SIZE=5.0 ------------------------------------------------------------------------------------------------------------------------------------ 14 TITAN-TRAIL NIC2 MULTIAC NIC2 POL240L SAMP-SEQ=STEP8,NSAMP=6, 1 DEF ING CUM PATTERN=ONE-CHOP,NUM-POS=2, CHOP-SIZE=5.0 ------------------------------------------------------------------------------------------------------------------------------------ 20 TITAN-TRAIL STIS/C ACQ F28X50L MIRROR ACQTYPE=DIFFUSE, 1 0.5 S ONBOARD ACQ FOR 30,40 ING CD P DIFFUSE-CENTER=GEOMETRIC-CENTER, CHECKBOX=9 ------------------------------------------------------------------------------------------------------------------------------------ 30 TITAN-TRAIL STIS/C ACCUM 52X0.1 G430L 4300 PATTERN=PERP-TO-SLIT,NUM-POS=3, 1 180 S ING CD STEP-SIZE=0.125, PATTERN-DIRECTION=PLUS,CR-SPLIT=2 ------------------------------------------------------------------------------------------------------------------------------------ 40 TITAN-TRAIL STIS/C ACCUM 52X0.1 G750L 7751 PATTERN=PERP-TO-SLIT,NUM-POS=3, 1 100 S ING CD STEP-SIZE=0.125, PATTERN-DIRECTION=PLUS,CR-SPLIT=2 Comments: Contemporaneous flat field requested for this exposure ------------------------------------------------------------------------------------------------------------------------------------ 7321( 7) - 10/02/97 16:50 - [ 11] Summary Form for Proposal 7321 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations NIC1 NIC2 STIS/CCD WFPC2 ------------------------------------------------------------------------------------------------------------------------------------ Opmodes MULTIACCUM ACQ IMAGE ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters SAMP-SEQ=STEP8 NSAMP=9 NSAMP=23 NSAMP=8 CHOP-SIZE=5.0 NUM-POS=2 PATTERN=ONE-CHOP NSAMP=6 CHECKBOX=9 CR-SPLIT=2 PATTERN-DIRECTION=PLUS GAIN=1 ATD-GAIN=7 ATD-GAIN=15 CR-SPLIT=1 CR-SPLIT=0.5 NSAMP=5 DIFFUSE-CENTER=GEOMETRIC-CENTER STEP-SIZE=0.125 NUM-POS=3 ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category SOLAR SYSTEM ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements ORIENT 25D TO 65D ONBOARD ACQ FOR 30,40 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F145M F164N POL0S POL120S POL240S F187N F190N F207M F212N F215N F216N POL0L POL120L POL240L MIRROR G430L G750L F336W F439W F547M F588N F673N FQCH4N15 FQCH4P15 ------------------------------------------------------------------------------------------------------------------------------------ Target Names TITAN-LEADING NONE TITAN TITAN-TRAILING ------------------------------------------------------------------------------------------------------------------------------------