10357( 42) - 12/29/04 11:27 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 10357 Version: 42 Check-in Date: 29-Dec-2004 16:26:21 1.Proposal Title: Saturn's Inner Satellites at True Opposition ------------------------------------------------------------------------------------ 2. Proposal For 3. Cycle 4. Parallel Pointing Tolerance GO/DD 13 ------------------------------------------------------------------------------------ 5. Investigators Contact? PI: Dr. Anne J. Verbiscer The University of Virginia CoI: Dr. Richard G. French Wellesley College N ------------------------------------------------------------------------------------ 6. Abstract We request one HST orbit to observe Janus, Epimetheus, Mimas, and Enceladus with WFPC2 exactly at opposition, when the Earth transits the center of the solar disk seen from Saturn on UT 13/14 January 2005. Data obtained at this unique viewing geometry are essential to determining physical properties of the moon's surface, related to its emplacement and evolution, and critical for the interpretation of photometric data obtained by Cassini at higher phase angles. This single observation will be the capstone of 9 years of legacy HST WFPC2 observations of the saturnian system (Cycles 6-12, R. French, PI) from which we have constructed precise, multiwavelength phase curves which demonstrate how the reflectance of these satellites varies with solar phase angle from 0.07 to 6.4 degrees. Each satellite exhibits a dramatic increase in brightness, or "opposition effect", as phase angles decrease below 1 degree. Since 1998 (Cycle 7) the minimum observable phase angle at opposition has decreased each year to 0.07 degrees in Cycle 12; however, the absolute minimum observable phase angle, about 0.02 degrees (limited by the angular size of the Sun viewed from Saturn), has not been accessible until Cycle 13. Using the same set of broadband filters for continuity with our previous programs, we will place observations made during the Earth transit on the existing UVBRI phase curves and establish the amplitude of each satellite's opposition surge. From these observations we will determine surface properties such as porosity, grain size distribution and particle opacity using radiative transfer models. While the Cassini spacecraft will obtain images at larger phase angles, it will miss entirely the narrow brightness surge near opposition due to orbital constraints. Because these inner satellites will be either lost in or contaminated by the glare of the fully open rings, they are not accessible to ground-based telescopes. The 2005 opposition prese nts the only opportunity for HST to observe the saturnian system during this rare planetary alignment. The next transit of Earth across the solar disk seen from Saturn occurs in 2020; the next central transit occurs in 2049. ------------------------------------------------------------------------------------ 10357( 42) - 12/29/04 11:27 - [ 2] Observations Description ------------------------ Visit 01 and 02 perform guide star acquisition tests for Visits 03 and 11. Visit 03 perfoms a Fixed Head Star Tracker (FHST) update with no ORIENT restrictions so Visit 11 can execute without a FHST update. The time critical observations of VIsit 11 must occur while the Earth transits the solar disk seen from Saturn. In this single visit, the first HST images of Saturn, its rings, and inner satellites at true opposition will be obtained using the F1042M, F336W, F439W, F555W, F675W, and F814W filters. Real Time Justification ----------------------- Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ 10357( 42) - 12/29/04 11:27 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 2 GUIDE-STAR- UNIDENTIFIED, RA=07H42M52.6000S +/- 0.1", J2000 V = 20.0 ACQ-TEST-1 UNDESIGNATED DEC=+21D21'0.00" +/- 0.1" Coordinate Source: Other_Source: Saturn Comments: Near the place in the sky were Saturn will be at the time that visit 11 executes. 3 GUIDE-STAR- UNIDENTIFIED, RA=07H43M19.0000S +/- 0.1", J2000 V = 20.0 ACQ-TEST-2 UNDESIGNATED DEC=+21D23'53.00" +/- 0.1" Coordinate Source: Other_Source: Saturn Comments: Near the place in the sky were Saturn will be at the time that visit 11 executes. 10357( 42) - 12/29/04 11:27 - [ 4] TARGET LIST Solar System Targets ------------------------------------------------------------------------------------------------------------------------------------ TARGET NUMBER: 1 | TARGET NAME: SATURN-OFFSET ------------------------------------------------------------------------------------------------------------------------------------ TARGET DESCRIPTION: OFFSET Saturn Offset ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 1 | TARGET POSITION LEVEL 2 | STD=SATURN | | ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 3 | WINDOWS | | ------------------------------------------------------------------------------------------------------------------------------------ DATA | COMMENTS | V = 0.9 | | ------------------------------------------------------------------------------------------------------------------------------------ 10357( 42) - 12/29/04 11:27 - [ 5] Visit: 01 Visit Priority: Visit Requirements: BEFORE 03-JAN-2005:00:00:00 On Hold Comments: Additional Comments: Perform a guide star acquisition test for one the guide stars to be used in visit 11. Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exp | Target | Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Num | Name | Config | Mode | or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 GUIDE-STAR- WFPC2 IMAGE PC1-FIX F1042M 1 1 S GSPAIR ACQ-TEST-1 0137301813F30000000000F0; GS ACQ SCENARIO SINGLE Comments: Guide star acquistion test for one of visit 11's guide stars. ------------------------------------------------------------------------------------------------------------------------------------ Sub Exposures ------------------------------------------------------------------------------------------------------------------------------------ Target | Exp |Instr | Oper. | Aper |Spectral|Cent.|Primary |Secondary |Iteration |CR-SPLIT |Orbit |Duration Name | Num |Config | Mode | or FOV |Element |Wave.|Pattern Pos |Pattern Pos |Num |Num |Number | ------------------------------------------------------------------------------------------------------------------------------------ GUIDE-STAR-ACQ-TES 1 WFPC2 IMAGE PC1-FIX F1042M none none none none 1 N/A T-1 10357( 42) - 12/29/04 11:27 - [ 6] Visit: 02 Visit Priority: Visit Requirements: BEFORE 03-JAN-2005:00:00:00 On Hold Comments: Additional Comments: Perform guide star acquisition tests for the guide stars to be used in visits 02 and 11. Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exp | Target | Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Num | Name | Config | Mode | or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 GUIDE-STAR- WFPC2 IMAGE PC1-FIX F1042M 1 1 S NEW OBSET FULL ACQ; ACQ-TEST-2 GSPAIR 0137302456F10000000000F0; GS ACQ SCENARIO SINGLE Comments: Guide star acquistion test for one of visit 11's guide stars. ------------------------------------------------------------------------------------------------------------------------------------ Sub Exposures ------------------------------------------------------------------------------------------------------------------------------------ Target | Exp |Instr | Oper. | Aper |Spectral|Cent.|Primary |Secondary |Iteration |CR-SPLIT |Orbit |Duration Name | Num |Config | Mode | or FOV |Element |Wave.|Pattern Pos |Pattern Pos |Num |Num |Number | ------------------------------------------------------------------------------------------------------------------------------------ GUIDE-STAR-ACQ-TES 1 WFPC2 IMAGE PC1-FIX F1042M none none none none 1 N/A T-2 10357( 42) - 12/29/04 11:27 - [ 7] Visit: 03 Visit Priority: Visit Requirements: NOTRACK On Hold Comments: Additional Comments: Visit 11 has problems scheduling in the desired orbit because of unfavorable windows for Fixed Head Star Tracker (FHST) updates. If the less restrictive visit 03 is scheduled just before visit 11, the FHST update will take place sooner; and there will not be an need for an FHST update between the two visits. Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exp | Target | Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Num | Name | Config | Mode | or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 SATURN-OFFS S/C POINTIN V1 1 1 S GSPAIR ET G 0137302437F10137300714F2 ------------------------------------------------------------------------------------------------------------------------------------ Sub Exposures ------------------------------------------------------------------------------------------------------------------------------------ Target | Exp |Instr | Oper. | Aper |Spectral|Cent.|Primary |Secondary |Iteration |CR-SPLIT |Orbit |Duration Name | Num |Config | Mode | or FOV |Element |Wave.|Pattern Pos |Pattern Pos |Num |Num |Number | ------------------------------------------------------------------------------------------------------------------------------------ SATURN-OFFSET 1 S/C POINTIN V1 none none none none 1 N/A G 10357( 42) - 12/29/04 11:27 - [ 8] Visit: 11 Visit Priority: Visit Requirements: SCHED 100%; ORIENT 133.0D TO 133.0 D; AFTER 03 BY 0.5 Orbits TO 1.5 Orbits; BETWEEN 13-JAN-2005:22:28:00 AND 14-JAN-2005:02:56:00 On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exp | Target | Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Num | Name | Config | Mode | or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 SATURN-OFFS WFPC2 IMAGE PC1-FIX F1042M 1 40 S POS TARG -13.021,-0.506 ET ------------------------------------------------------------------------------------------------------------------------------------ 2 SATURN-OFFS WFPC2 IMAGE PC1-FIX F336W 1 30 S SAME POS AS 1 ET ------------------------------------------------------------------------------------------------------------------------------------ 3 SATURN-OFFS WFPC2 IMAGE PC1-FIX F555W 1 0.11 S SAME POS AS 1 ET ------------------------------------------------------------------------------------------------------------------------------------ 4 SATURN-OFFS WFPC2 IMAGE PC1-FIX F439W 2 5 S SAME POS AS 1; NEW ET ALIGNMENT ------------------------------------------------------------------------------------------------------------------------------------ 5 SATURN-OFFS WFPC2 IMAGE PC1-FIX F439W 1 1 S SAME POS AS 1 ET ------------------------------------------------------------------------------------------------------------------------------------ 6 SATURN-OFFS WFPC2 IMAGE PC1-FIX F555W 2 1 S SAME POS AS 1 ET ------------------------------------------------------------------------------------------------------------------------------------ 7 SATURN-OFFS WFPC2 IMAGE PC1-FIX F555W 1 0.4 S SAME POS AS 1 ET ------------------------------------------------------------------------------------------------------------------------------------ 8 SATURN-OFFS WFPC2 IMAGE PC1-FIX F814W 1 1 S POS TARG -15.273,-2.366; ET NEW ALIGNMENT ------------------------------------------------------------------------------------------------------------------------------------ 9 SATURN-OFFS WFPC2 IMAGE PC1-FIX F814W 2 0.4 S SAME POS AS 8; NEW ET ALIGNMENT ------------------------------------------------------------------------------------------------------------------------------------ 10 SATURN-OFFS WFPC2 IMAGE PC1-FIX F675W 1 1 S SAME POS AS 8 ET ------------------------------------------------------------------------------------------------------------------------------------ 11 SATURN-OFFS WFPC2 IMAGE PC1-FIX F675W 1 0.35 S SAME POS AS 8 ET ------------------------------------------------------------------------------------------------------------------------------------ 12 SATURN-OFFS WFPC2 IMAGE PC1-FIX F675W 1 0.11 S SAME POS AS 8 ET ------------------------------------------------------------------------------------------------------------------------------------ 10357( 42) - 12/29/04 11:27 - [ 9] Sub Exposures ------------------------------------------------------------------------------------------------------------------------------------ Target | Exp |Instr | Oper. | Aper |Spectral|Cent.|Primary |Secondary |Iteration |CR-SPLIT |Orbit |Duration Name | Num |Config | Mode | or FOV |Element |Wave.|Pattern Pos |Pattern Pos |Num |Num |Number | ------------------------------------------------------------------------------------------------------------------------------------ Sub Exposures ------------------------------------------------------------------------------------------------------------------------------------ Target | Exp |Instr | Oper. | Aper |Spectral|Cent.|Primary |Secondary |Iteration |CR-SPLIT |Orbit |Duration Name | Num |Config | Mode | or FOV |Element |Wave.|Pattern Pos |Pattern Pos |Num |Num |Number | ------------------------------------------------------------------------------------------------------------------------------------ SATURN-OFFSET 1 WFPC2 IMAGE PC1-FIX F1042M none none none none 1 N/A SATURN-OFFSET 2 WFPC2 IMAGE PC1-FIX F336W none none none none 1 N/A SATURN-OFFSET 3 WFPC2 IMAGE PC1-FIX F555W none none none none 1 N/A SATURN-OFFSET 4 WFPC2 IMAGE PC1-FIX F439W none none 1 none 1 N/A SATURN-OFFSET 4 WFPC2 IMAGE PC1-FIX F439W none none 2 none 1 N/A SATURN-OFFSET 5 WFPC2 IMAGE PC1-FIX F439W none none none none 1 N/A SATURN-OFFSET 6 WFPC2 IMAGE PC1-FIX F555W none none 1 none 1 N/A SATURN-OFFSET 6 WFPC2 IMAGE PC1-FIX F555W none none 2 none 1 N/A SATURN-OFFSET 7 WFPC2 IMAGE PC1-FIX F555W none none none none 1 N/A SATURN-OFFSET 8 WFPC2 IMAGE PC1-FIX F814W none none none none 1 N/A SATURN-OFFSET 9 WFPC2 IMAGE PC1-FIX F814W none none 1 none 1 N/A SATURN-OFFSET 9 WFPC2 IMAGE PC1-FIX F814W none none 2 none 1 N/A SATURN-OFFSET 10 WFPC2 IMAGE PC1-FIX F675W none none none none 1 N/A SATURN-OFFSET 11 WFPC2 IMAGE PC1-FIX F675W none none none none 1 N/A SATURN-OFFSET 12 WFPC2 IMAGE PC1-FIX F675W none none none none 1 N/A 10357( 42) - 12/29/04 11:27 - [ 10] Summary Form for Proposal 10357 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures PC1-FIX V1 ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFPC2 S/C ------------------------------------------------------------------------------------------------------------------------------------ Opmodes IMAGE POINTING ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO/DD ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements BEFORE 03-JAN-2005 00 00 00 GSPAIR 0137301813F30000000000F0; GS ACQ SCENARIO SINGLE BEFORE 03-JAN-2005 00 00 00 NEW OBSET FULL ACQ; GSPAIR 0137302456F10000000000F0; GS ACQ SCENARIO SINGLE NOTRACK GSPAIR 0137302437F10137300714F2 SCHED 100%; ORIENT 133.0D TO 133.0 D; AFTER 03 BY 0.5 Orbits TO 1.5 Orbits; BETWEEN 13-JAN-2005 22 28 00 AND 14-JAN-2005 02 56 00 POS TARG -13.021,-0.506 SAME POS AS 1 SAME POS AS 1; NEW ALIGNMENT POS TARG -15.273,-2.366; NEW ALIGNMENT SAME POS AS 8; NEW ALIGNMENT SAME POS AS 8 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F1042M F336W F555W F439W F814W F675W ------------------------------------------------------------------------------------------------------------------------------------ Target Names GUIDE-STAR-ACQ-TEST-1 GUIDE-STAR-ACQ-TEST-2 SATURN-OFFSET ------------------------------------------------------------------------------------------------------------------------------------