8117( 19) - 01/04/01 15:13 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 8117 Version: 19 Check-in Date: 04-Jan-2001 15:12:31 1.Proposal Title: Saturn's Far UV Aurora and Polar Hazes ------------------------------------------------------------------------------------ 2. Proposal For 3. Cycle GO 8 ------------------------------------------------------------------------------------ 4. Investigators Contact? PI: John Trauger Jet Propulsion Laboratory CoI: Dr. John Clarke University of Michigan N CoI: Dr. Gilda Ballester University of Michigan N CoI: Dr. Lotfi Ben Jaffel Institut d'Astrophysique de Paris N CoI: Dr. Karl Stapelfeldt Jet Propulsion Laboratory N CoI: Dr. Robin Evans Jet Propulsion Laboratory N ------------------------------------------------------------------------------------ 5. Abstract We propose to carry out a coordinated program of STIS imaging and spectroscopy in the FUV and NUV during one full rotation of the planet in order to capture a complete picture of the south auroral emission region on Saturn. FUV imaging and chapman-profile modeling is our lever to characterize emissions from above the homopause, while FUV and NUV spectroscopy and radiative transfer modeling will describe the atmospheric phenomena driven by particle radiation that penetrates below the homopause. The proposed observation is a direct extension of a program of WFPC2 and STIS imaging begun in Cycles 6 and 7. Very little is presently known about the range of possible morphologies and temporal behaviors in the Saturn aurora. One complete rotation is required to sort out the planet-fixed and local-time-fixed characteristics, and to provide spectra with sufficient S/N to reliably constrain the radiative transfer modeling. ------------------------------------------------------------------------------------ 8117( 19) - 01/04/01 15:13 - [ 2] Observations Description ------------------------ Each orbit of observing will consist of one FUV spectrum (G140L), and either one FUV image (25SRF2) or one NUV spectrum (G230LB). Bright object limits for the NUV require that the CCD mode be used for the NUV spectrum. The 25SRF2 image mode provides the location of the molecular H2 auroral emissions, which indicates the center of the auroral arcs for both the H Ly-alpha and molecular H2. The 2-arcsec spectrograph slit is specified for G140L and the 0.5-arcsecond slit is specified for G230LB. The slits are oriented parallel to Saturn's north -south axis to provide spatially resolved spectra of the auroral emission latitudes, lower latitudes across the disk, the rings, and the geocoronal/interplanetary background. The slit is offset a ~2 arcseconds eastward of the rotational axis as required to center on the south aurora near 0600 local time. The wide G140L slit with eastern offset provides an auroral field of view that is comfortably larger than the ~1-arcsec range of latitude wander observed in the auroral arcs in Cycle 7 images. The narrower G230LB slit provides spectral resolving power sufficient to constrain the atmospheric modeling. The length of the slit covers a range of latitudes extending from low latitudes free of the polar haze to the high latitudes of the auroral arc, in order to better constrain the polar haze model. The orientation of the slit allows the summation of ~100 pixel rows, which together with the 2-arcsec slit width will provide a S/N of about 5 in a 1000-second exposure across the FUV wavelengths longward of 1350 Angstroms that are needed to constrain the radiative model, based on a quantitative simulation with a nominal synthetic Saturn spectrum. Multiple spectra combined with images to confirm auroral pointing accuracy works to reduce systematic errors, and summing of spectra will further improve the S/N by another factor of 3. The full rotational coverage provides a long lever to separate anticipated auroral systematics that follow local-time, planet longitude, possible satellite interactions, and random events. Obtaining images and spectra in each orbit makes it possible to verify the current location of the aurora, and to know the position of the slit relative to the emission morphology. With a -19.9 degrees sub-earth latitude, the 1999 Saturn apparition provides the best view of an auroral zone on Saturn since the HST servicing mission in 1993. This will greatly improve our ability to sort out the latitude/altitude and longitude/latitude ambiguities that arise with a more oblique view of the polar regions. The following geometry constraints are specified: 1. The image sequence should be taken close to opposition to minimize the geocoronal H Lyman alpha background (maximize shadow time) and also to maximize the apparent size of the disk. 2. STIS MAMA operations are restricted to five or less consecutive SAA-free orbits per day. Given this 5-orbit window, the 8-orbit Saturn observation sequence are best broken into two visits, each consisting of 4 consecutive orbits. 3. No constraints are placed on Saturn longitude during the first visit, but a time delay of [(n + 0.5) * 639 minutes] is required between the start of the first visit and start of the second visit (where n is as small an integer as possible), in oder to provide effective coverage of one complete Saturn rotation (period is 639 minutes). 4. STIS spectra will be taken with the long slit aligned parallel to the central meridian (i.e. N-S) and offset eastward by 2 arcsec to cover the morning sector of Saturn's south polar auroral zone. 5. A POSTARG displacement is specified to place the long slit over the south polar aurora zone at 0600 local time. This generates an RPS2 diagnostic (offset greater than the width of the slit), but the offset is intended. Real Time Justification ----------------------- The G140L spectroscopy and 25MAMA imaging needs to be done in shadow time. In most orbits, it will be possible to schedule exposures in pairs, with one exposure in shadow that includes H Ly-alpha (G140L) and a second unrestricted exposure that excludes H Ly-alpha (G230LB or F25SRF2). The order of these pairings is determined by the observing date (i.e. before or after Saturn opposition on November 6, 1999) once the scheduling window is known. The observations are grouped into two visits, each consisting of four consecutive orbits, with timing between the visits constrained to provide continuity over a full rotation of Saturn. The observation is scheduled within a month of opposition. Calibration Justification ------------------------- Additional Comments ------------------- A number of details in the observing sequence will be known only when the observing dates have been selected. These TBD parameters are as follows: 1. Bright object avoidance scheduling windows must be determined. 2. The second visit is constrained to begin when Saturn has rotated (180 + n*360) degrees from the start of the first visit, where n=1 if possible, corresponding to (319 + 639*n) minutes after the start of the first visit. 3. The placement of the G140L spectra in each orbit depends on whether earth shadow occurs at the beginning or end of the orbit. If the observations are scheduled following the date of Saturn opposition on 6 November 1999, then shadow occurs at the end of each orbit, and the G140L exposure is the last science exposure in the orbit (this is assumed in the RPS2 proposal below). If the observations occur before opposition, then the G140L exposures need to be moved to the start of each orbit (i.e. the proposal needs to be revised from its present form). 4. The slit must be oriented parallel to Saturn's central meridian. ------------------------------------------------------------------------------------ 8117( 19) - 01/04/01 15:13 - [ 3] Data Distribution Paper Products: NO Media: ELECTRONIC Blocking Factor: 10 Ship To: PI_Address Ship Via: Email: ------------------------------------------------------------------------------------ 8117( 19) - 01/04/01 15:13 - [ 4] TARGET LIST Solar System Targets ------------------------------------------------------------------------------------------------------------------------------------ TARGET NUMBER: 1 | TARGET NAME: SAT-AUR ------------------------------------------------------------------------------------------------------------------------------------ TARGET DESCRIPTION: PLANET SATURN ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 1 | TARGET POSITION LEVEL 2 | STD=SATURN | | ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 3 | WINDOWS | | ------------------------------------------------------------------------------------------------------------------------------------ DATA | COMMENTS | V = -0.6+/-0.5 | F-LINE(1400)=1+/-1e-14 | W-LINE(1400)=420 | F-CONT(1800)=4+/-5e-13 | SIZE=16+/-13 | F-CONT(5500)=7.8+/-5e-12 | SIZE=1.1 | | ------------------------------------------------------------------------------------------------------------------------------------ TARGET NUMBER: 2 | TARGET NAME: TITAN ------------------------------------------------------------------------------------------------------------------------------------ TARGET DESCRIPTION: SATELLITE ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 1 | TARGET POSITION LEVEL 2 | STD=SATURN | STD=TITAN | ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 3 | WINDOWS | | ------------------------------------------------------------------------------------------------------------------------------------ DATA | COMMENTS | SURF(V) = 7.8+/-0.3 | | ------------------------------------------------------------------------------------------------------------------------------------ 8117( 19) - 01/04/01 15:13 - [ 5] Visit: 01 Visit Priority: Visit Requirements: SCHED 70%; ORIENT 67D TO 67D; between 28-Jan-2001:08:20:00 and 31-Jan- 2001:17:50:00 On Hold Comments: Additional Comments: ORIENT 43D (after Nov 6 2000) based on Saturn's north polar Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 11 TITAN STIS/C ACQ F28X50L MIRROR ACQTYPE=DIFFUSE,CHECKBOX=19, 1 0.1 S CD P DIFFUSE-CENTER=GEOMETRIC-CENTER Comments: Diam=0.83", Peak=5680 e-, S/N=1875, ETC 15510 ------------------------------------------------------------------------------------------------------------------------------------ 12 SAT-AUR STIS/F TIME-TA F25SRF2 MIRROR BUFFER-TIME=100 1 330 S UV-MAM G A ------------------------------------------------------------------------------------------------------------------------------------ 13 SAT-AUR STIS/F TIME-TA 52X2 G140L 1425 BUFFER-TIME=1000 1 1000 S POS TARG -2.0, 0.0 UV-MAM G A ------------------------------------------------------------------------------------------------------------------------------------ 21 SAT-AUR STIS/C ACCUM 52X0.5 G230LB 2375 1 680 S POS TARG -2.0, 0.0 CD ------------------------------------------------------------------------------------------------------------------------------------ 22 SAT-AUR STIS/F TIME-TA 52X2 G140L 1425 BUFFER-TIME=600 1 1200 S POS TARG -2.0, 0.0 UV-MAM G A ------------------------------------------------------------------------------------------------------------------------------------ 31 SAT-AUR STIS/F TIME-TA F25SRF2 MIRROR BUFFER-TIME=100 1 600 S UV-MAM G A ------------------------------------------------------------------------------------------------------------------------------------ 32 SAT-AUR STIS/F TIME-TA 52X2 G140L 1425 BUFFER-TIME=700 1 1400 S POS TARG -2.0, 0.0 UV-MAM G A ------------------------------------------------------------------------------------------------------------------------------------ 41 SAT-AUR STIS/C ACCUM 52X0.5 G230LB 2375 1 680 S POS TARG -2.0, 0.0 CD ------------------------------------------------------------------------------------------------------------------------------------ 42 SAT-AUR STIS/F TIME-TA 52X2 G140L 1425 BUFFER-TIME=600 1 1200 S POS TARG -2.0, 0.0 UV-MAM G A ------------------------------------------------------------------------------------------------------------------------------------ 8117( 19) - 01/04/01 15:13 - [ 6] Visit: 02 Visit Priority: Visit Requirements: SCHED 70%; after 1 by 25h to 28h ORIENT 67D TO 67D; between 29-Jan- 2001:08:20:00 and 01-Feb-2001:16:20:00 On Hold Comments: Additional Comments: and [81, 82] repectively. Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 51 TITAN STIS/C ACQ F28X50L MIRROR ACQTYPE=DIFFUSE,CHECKBOX=19, 1 0.1 S CD P DIFFUSE-CENTER=GEOMETRIC-CENTER Comments: Diam=0.83", Peak=5680 e-, S/N=1875, ETC 15510 ------------------------------------------------------------------------------------------------------------------------------------ 52 SAT-AUR STIS/F TIME-TA F25SRF2 MIRROR BUFFER-TIME=100 1 300 S UV-MAM G A ------------------------------------------------------------------------------------------------------------------------------------ 53 SAT-AUR STIS/F TIME-TA 52X2 G140L 1425 BUFFER-TIME=1000 1 1000 S POS TARG -5.2, 0.0 UV-MAM G A ------------------------------------------------------------------------------------------------------------------------------------ 61 SAT-AUR STIS/C ACCUM 52X0.5 G230LB 2375 1 680 S POS TARG -5.2, 0.0 CD ------------------------------------------------------------------------------------------------------------------------------------ 62 SAT-AUR STIS/F TIME-TA 52X2 G140L 1425 BUFFER-TIME=600 1 1200 S POS TARG -5.2, 0.0 UV-MAM G A ------------------------------------------------------------------------------------------------------------------------------------ 71 SAT-AUR STIS/F TIME-TA F25SRF2 MIRROR BUFFER-TIME=100 1 600 S UV-MAM G A ------------------------------------------------------------------------------------------------------------------------------------ 72 SAT-AUR STIS/F TIME-TA 52X2 G140L 1425 BUFFER-TIME=700 1 1400 S POS TARG -5.2, 0.0 UV-MAM G A ------------------------------------------------------------------------------------------------------------------------------------ 81 SAT-AUR STIS/C ACCUM 52X0.5 G230LB 2375 1 680 S POS TARG -5.2, 0.0 CD ------------------------------------------------------------------------------------------------------------------------------------ 82 SAT-AUR STIS/F TIME-TA 52X2 G140L 1425 BUFFER-TIME=600 1 1200 S POS TARG -5.2, 0.0 UV-MAM G A ------------------------------------------------------------------------------------------------------------------------------------ 8117( 19) - 01/04/01 15:13 - [ 7] Visit: 11 Visit Priority: Visit Requirements: SCHED 70%; ORIENT 67D TO 67D; between 28-Jan-2001:08:20:00 and 31-Jan- 2001:17:50:00 On Hold Comments: Additional Comments: ORIENT 43D (after Nov 6 2000) based on Saturn's north polar Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 11 TITAN STIS/C ACQ F28X50L MIRROR ACQTYPE=DIFFUSE,CHECKBOX=19, 1 0.1 S CD P DIFFUSE-CENTER=GEOMETRIC-CENTER Comments: Diam=0.83", Peak=5680 e-, S/N=1875, ETC 15510 ------------------------------------------------------------------------------------------------------------------------------------ 12 SAT-AUR STIS/F TIME-TA F25SRF2 MIRROR BUFFER-TIME=100 1 330 S UV-MAM G A ------------------------------------------------------------------------------------------------------------------------------------ 13 SAT-AUR STIS/F TIME-TA 52X2 G140L 1425 BUFFER-TIME=1000 1 1000 S POS TARG -5.2, 0.0 UV-MAM G A ------------------------------------------------------------------------------------------------------------------------------------ 21 SAT-AUR STIS/C ACCUM 52X0.5 G230LB 2375 1 680 S POS TARG -5.2, 0.0 CD ------------------------------------------------------------------------------------------------------------------------------------ 22 SAT-AUR STIS/F TIME-TA 52X2 G140L 1425 BUFFER-TIME=600 1 1200 S POS TARG -5.2, 0.0 UV-MAM G A ------------------------------------------------------------------------------------------------------------------------------------ 31 SAT-AUR STIS/F TIME-TA F25SRF2 MIRROR BUFFER-TIME=100 1 600 S UV-MAM G A ------------------------------------------------------------------------------------------------------------------------------------ 32 SAT-AUR STIS/F TIME-TA 52X2 G140L 1425 BUFFER-TIME=700 1 1400 S POS TARG -5.2, 0.0 UV-MAM G A ------------------------------------------------------------------------------------------------------------------------------------ 41 SAT-AUR STIS/C ACCUM 52X0.5 G230LB 2375 1 680 S POS TARG -5.2, 0.0 CD ------------------------------------------------------------------------------------------------------------------------------------ 42 SAT-AUR STIS/F TIME-TA 52X2 G140L 1425 BUFFER-TIME=600 1 1200 S POS TARG -5.2, 0.0 UV-MAM G A ------------------------------------------------------------------------------------------------------------------------------------ 8117( 19) - 01/04/01 15:13 - [ 8] Summary Form for Proposal 8117 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures F28X50LP F25SRF2 52X2 52X0.5 ------------------------------------------------------------------------------------------------------------------------------------ Configurations STIS/CCD STIS/FUV-MAMA ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ TIME-TAG ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters ACQTYPE=DIFFUSE CHECKBOX=19 DIFFUSE-CENTER=GEOMETRIC-CENTER BUFFER-TIME=100 BUFFER-TIME=1000 BUFFER-TIME=600 BUFFER-TIME=700 ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements SCHED 70%; ORIENT 67D TO 67D; between 28-Jan-2001 08 20 00 and 31-Jan-2001 17 50 00 POS TARG -2.0, 0.0 SCHED 70%; after 1 by 25h to 28h ORIENT 67D TO 67D; between 29-Jan-2001 08 20 00 and 01-Feb-2001 16 20 00 POS TARG -5.2, 0.0 SCHED 70%; ORIENT 67D TO 67D; between 28-Jan-2001 08 20 00 and 31-Jan-2001 17 50 00 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements MIRROR G140L G230LB ------------------------------------------------------------------------------------------------------------------------------------ Target Names TITAN SAT-AUR ------------------------------------------------------------------------------------------------------------------------------------ Wavelengths 1425 2375 ------------------------------------------------------------------------------------------------------------------------------------