9035( 20) - 01/28/02 06:54 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 9035 Version: 20 Check-in Date: 28-Jan-2002 06:53:55 1.Proposal Title: Spatially Resolved Spectroscopy of Uranus and Neptune ------------------------------------------------------------------------------------ 2. Proposal For 3. Cycle GO 10 ------------------------------------------------------------------------------------ 4. Investigators Contact? PI: Erich Karkoschka University of Arizona CoI: Dr. Mark Lemmon Texas A&M University N CoI: Dr. Martin Tomasko University of Arizona N ------------------------------------------------------------------------------------ 5. Abstract We propose to use STIS to obtain data cubes for Uranus (Cycle 10) and Neptune (Cycle 11). The spectrum between 290 and 1020 nm is sampled at 2000 wavelengths. The north- south position on the planetary disk is sampled along the slit every 0.05". The east -west position is sampled by successive exposures every 0.05" (longward of 520 nm wavelength) and 0.15" (shortward of 520 nm). Such data have never been obtained. Only HST, with STIS, has the capability to record spatial variations of narrow methane and hydrogen absorption and Raman scattering features. We have obtained such data for Saturn by ground-based observations which permitted a comprehensive understanding of the vertical haze and cloud structure as a function of latitude. Similar improvements are expected from the proposed data for Uranus and Neptune. HST has revealed exciting images of Uranus and Neptune while their quantitative analysis has been slow due to limitations in available filters. Our short, spatially-resolved spectroscopic program will reveal accurate spectral shapes across each WFPC2 filter which then will greatly improve the reliability of interpretations based on hundreds of past and future WFPC2 images. Similarly, WFPC2 images of Titan required the addition of STIS spectra before the latest improvements in our understanding of its atmosphere were possible. ------------------------------------------------------------------------------------ 9035( 20) - 01/28/02 06:54 - [ 2] Observations Description ------------------------ Cycle 10: During the first orbit, we will use STIS with grating G430L and a 0.1" slit for wavelengths 290-570 nm and 1 min exposure time each. The slit orientation with be parallel to the central meridian. Considering overhead times, 13 positions will be possible distributed between the central meridian and the evening limb equally spaced by 0.15". At wavelengths below 540 nm, Uranus does not display much latitudinal contrasts. Thus, the significant center-to- limb variations are expected to be well recorded by those slit positions. For the next two orbits, we propose to use STIS with grating G750L and 0.1" slit for wavelengths 524- 1027 nm and 1 min exposure time each. Sampling the 1.85" radius of Uranus at 0.05" sampling from central meridian to evening limb with an additional exposure on each side to account for impecfect centering in the acquisition requires 40 exposures (20 per orbit). We plan to read out only 7" around Uranus to reduce overhead times. For both gratings, we expect about 5, 000 electrons per pixel at the brightest part of Uranus at the brightest wavelength, which typically gives signal-to-noise ratios of 50 per pixel. The gain 1 setting will be used. Overhead times for the first orbit: guide star acquisition (6 min), target acquisition (10 min), exposure overheads (5 + 12*1 = 17 min), small angle offsets (12*0.33 = 4 min), exposure times (13*1 = 13 min), totaling 50 min. Overhead times for the second and third orbit: guide star reacquisition (5 min), exposure overheads (5 + 19*1 = 24 min), small angle offsets (19*0.33 = 6 min), exposure times (20*1 = 20 min), totaling 55 min. Both gratings will require wavelength calibration exposures (wavecal) which will be scheduled during the occultation periods between orbits. The G750L grating will require flatfields (fringe flat) which also will be scheduled between orbits. Overhead for data management will not be required since we will read out only 140 rows. The target acquisition will be a diffuse acquisition on Uranus with flux-centered checkbox of 33 pixels with aperture F28X50LP and 5 sec exposure time. The target acquisition exposure will help in the navigation of the exposures with the G750L grating. The overlapping spectral region will facilitate navigation of the remaining exposures. We tested our target acquisition method with WFPC2 images in 21 different filters. The root-mean-square deviation in east-west centering between our acquisition method and a limb fitting method was 0.03". The deviation was only 0.02" for an average image of many red and near-infrared WFPC2 images which approximates the throughput of the F28X50LP aperture. Thus, we are confindent that centering on Uranus will be more accurate than required. Cycle 11: We will use the same observing technique as in Cycle 10, but this time for Neptune instead of Uranus. Neptune requires exposure times three times as long as for Uranus to reach similar exposure levels. The first orbit allows 8 exposures with 4 minute exposure time each which is sufficient. The spacing between different slit positions is 0.15". Sampling with the G750L grating every 0.05" requires 24 slit positions between central meridian and evening limb. With two remaining orbits as for Uranus, this would yield 12 exposures each with 2 minute exposure time which would compromise the signal-to-noise ratio. Therefore, we ask for an additional orbit for Neptune which extends the observations with grating G750L to three orbits with 8 exposures each of 4 minute exposure time. Real Time Justification ----------------------- Time-critical observations: In order to take advantage of the almost perfect east-west symmetry of Uranus (to a lesser degree of Neptune), the slit needs to be aligned along the central meridians. This restricts scheduling of the observations within a few days and about a month of opposition for Uranus and Neptune, respectively. Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ 9035( 20) - 01/28/02 06:54 - [ 3] TARGET LIST Solar System Targets ------------------------------------------------------------------------------------------------------------------------------------ TARGET NUMBER: 1 | TARGET NAME: URANUS-CENTER-OF-LIGHT ------------------------------------------------------------------------------------------------------------------------------------ TARGET DESCRIPTION: OFFSET URANUS ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 1 | TARGET POSITION LEVEL 2 | STD=URANUS | TYPE=POS_ANGLE,RAD=0.5,ANG=78.5,REF=NORT | H | ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 3 | WINDOWS | | ------------------------------------------------------------------------------------------------------------------------------------ DATA | COMMENTS | V = 5.7 | Uranus Central Meridian, 0.5" B-V = 0.6 | towards south pole | ------------------------------------------------------------------------------------------------------------------------------------ TARGET NUMBER: 2 | TARGET NAME: URANUS-MOSAIC-BLUE ------------------------------------------------------------------------------------------------------------------------------------ TARGET DESCRIPTION: OFFSET URANUS ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 1 | TARGET POSITION LEVEL 2 | STD=URANUS | TYPE=POS_ANGLE,RAD=1.8252,ANG=348.5,REF= | NORTH | ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 3 | WINDOWS | | ------------------------------------------------------------------------------------------------------------------------------------ DATA | COMMENTS | V = 5.7 | Uranus mosaic from evening limb to B-V = 0.6 | center | ------------------------------------------------------------------------------------------------------------------------------------ 9035( 20) - 01/28/02 06:54 - [ 4] TARGET LIST Solar System Targets ------------------------------------------------------------------------------------------------------------------------------------ TARGET NUMBER: 3 | TARGET NAME: URANUS-MOSAIC-RED-1 ------------------------------------------------------------------------------------------------------------------------------------ TARGET DESCRIPTION: OFFSET URANUS ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 1 | TARGET POSITION LEVEL 2 | STD=URANUS | TYPE=POS_ANGLE,RAD=1.9266,ANG=348.5,REF= | NORTH | ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 3 | WINDOWS | | ------------------------------------------------------------------------------------------------------------------------------------ DATA | COMMENTS | V = 5.7 | Uranus mosaic from evening limb B-V = 0.6 | towards center | ------------------------------------------------------------------------------------------------------------------------------------ TARGET NUMBER: 4 | TARGET NAME: URANUS-MOSAIC-RED-2 ------------------------------------------------------------------------------------------------------------------------------------ TARGET DESCRIPTION: OFFSET URANUS ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 1 | TARGET POSITION LEVEL 2 | STD=URANUS | TYPE=POS_ANGLE,RAD=0.9126,ANG=348.5,REF= | NORTH | ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 3 | WINDOWS | | ------------------------------------------------------------------------------------------------------------------------------------ DATA | COMMENTS | V = 5.7 | Uranus mosaic from afternoon side to B-V = 0.6 | center | ------------------------------------------------------------------------------------------------------------------------------------ 9035( 20) - 01/28/02 06:54 - [ 5] Patterns ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 1 Primary_Pattern Secondary_Pattern Pattern_Type LINE Pattern_Purpose MOSAIC Number_Of_Points 13 Point_Spacing 0.1521 Coordinate_Frame CELESTIAL Pattern_Orient 168.5 Center_Pattern NO ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 2 Primary_Pattern Secondary_Pattern Pattern_Type LINE Pattern_Purpose MOSAIC Number_Of_Points 20 Point_Spacing 0.0507 Coordinate_Frame CELESTIAL Pattern_Orient 168.5 Center_Pattern NO ------------------------------------------------------------------------------------------------------------------------------------ 9035( 20) - 01/28/02 06:54 - [ 6] Visit: 01 Visit Priority: Visit Requirements: SCHED 100% ORIENT 303.4D TO 303.6D On Hold Comments: Additional Comments: Slit-orientation must be parallel to the rotation axis of Uranus (PA = 78.53 deg in mid August 2002) to use Uranus' east-west symmetry. Check comments of exposures 22 and 32 Exposure times of exposures 12, 22, and 32 may be slightly adjusted in case of longer or shorter than expected visibility periods. Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 URANUS-CENT STIS/C ACQ F28X50L MIRROR ACQTYPE=DIFFUSE , 1 5 S ER-OF-LIGHT CD P DIFFUSE-CENTER=FLUX-CENTROID , CHECKBOX=33 ------------------------------------------------------------------------------------------------------------------------------------ 12 URANUS-MOSA STIS/C ACCUM 52X0.1 G430L 4300 SIZEAXIS2=140 ,CR-SPLIT=NO , 1 87 S PATTERN 1 NO SPLIT IC-BLUE CD WAVECAL=NO ------------------------------------------------------------------------------------------------------------------------------------ 13 WAVE STIS/C ACCUM 52X0.1 G430L 4300 1 DEF CD ------------------------------------------------------------------------------------------------------------------------------------ 20 CCDFLAT STIS/C ACCUM 52X0.1 G750L 7751 2 DEF CD Comments: Preferably scheduled close to exposure 22 ------------------------------------------------------------------------------------------------------------------------------------ 21 WAVE STIS/C ACCUM 52X0.1 G750L 7751 1 DEF CD Comments: Preferably scheduled close to exposure 22 ------------------------------------------------------------------------------------------------------------------------------------ 22 URANUS-MOSA STIS/C ACCUM 52X0.1 G750L 7751 SIZEAXIS2=140 ,CR-SPLIT=NO 1 87 S PATTERN 2 NO SPLIT MAX IC-RED-1 CD DUR 240S Comments: Sp_Element must be G750L, Wavelength 7751 ------------------------------------------------------------------------------------------------------------------------------------ 23 WAVE STIS/C ACCUM 52X0.1 G750L 7751 1 DEF CD ------------------------------------------------------------------------------------------------------------------------------------ 24 CCDFLAT STIS/C ACCUM 52X0.1 G750L 7751 2 DEF CD ------------------------------------------------------------------------------------------------------------------------------------ 30 CCDFLAT STIS/C ACCUM 52X0.1 G750L 7751 2 DEF CD Comments: Preferably scheduled close to exposure 32 ------------------------------------------------------------------------------------------------------------------------------------ 31 WAVE STIS/C ACCUM 52X0.1 G750L 7751 1 DEF CD Comments: Preferably scheduled close to exposure 32 ------------------------------------------------------------------------------------------------------------------------------------ 32 URANUS-MOSA STIS/C ACCUM 52X0.1 G750L 7751 SIZEAXIS2=140 ,CR-SPLIT=NO 1 87 S PATTERN 2 NO SPLIT MAX IC-RED-2 CD DUR 240S Comments: Sp_Element must be G750L, Wavelength 7751 ------------------------------------------------------------------------------------------------------------------------------------ 9035( 20) - 01/28/02 06:54 - [ 7] Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 33 WAVE STIS/C ACCUM 52X0.1 G750L 7751 1 DEF CD ------------------------------------------------------------------------------------------------------------------------------------ 34 CCDFLAT STIS/C ACCUM 52X0.1 G750L 7751 2 DEF CD ------------------------------------------------------------------------------------------------------------------------------------ 9035( 20) - 01/28/02 06:54 - [ 8] Summary Form for Proposal 9035 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures F28X50LP 52X0.1 ------------------------------------------------------------------------------------------------------------------------------------ Configurations STIS/CCD ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters ACQTYPE=DIFFUSE DIFFUSE-CENTER=FLUX-CENTROID CHECKBOX=33 WAVECAL=NO CR-SPLIT=NO SIZEAXIS2=140 ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements SCHED 100% ORIENT 303.4D TO 303.6D PATTERN 1 NO SPLIT PATTERN 2 NO SPLIT MAX DUR 240S ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements MIRROR G430L G750L ------------------------------------------------------------------------------------------------------------------------------------ Target Names URANUS-CENTER-OF-LIGHT URANUS-MOSAIC-BLUE WAVE CCDFLAT URANUS-MOSAIC-RED-1 URANUS-MOSAIC-RED-2 ------------------------------------------------------------------------------------------------------------------------------------ Wavelengths 4300 7751 ------------------------------------------------------------------------------------------------------------------------------------