16418( 12) - 20-Jul-2020 19:36:20 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 16418 Version: 12 Check-in Time: 20-Jul-2020 19:36:20 STScI Edit Number: 7 Title Bright Near-Sun Comet C/2020 F3 (NEOWISE) ------------------------------------------------------------------------------------ Type Cycle GO/DD 27 ------------------------------------------------------------------------------------ Investigators Contact? PI: Qicheng Zhang California Institute of Technology Y CoI: Dr. Quanzhi Ye University of Maryland N CoI: Dr. Ludmilla Kolokolova University of Maryland N CoI: Dr. Matthew M Knight United States Naval Academy N CoI: Prof. Gregg Hallinan California Institute of Technology N ------------------------------------------------------------------------------------ Abstract C/2020 F3 (NEOWISE) is the brightest near-Sun comet to survive perihelion in over a decade, and since its post-conjunction recovery from the ground in early 2020 July, has displayed a morphology that is characteristic of many of the brightest and most active such comets in history. Moreover, C/2020 F3 features post-perihelion observing geometry that is unusually favorable for a near-Sun comet, leaving the 55 degree solar exclusion zone of HST only one month past perihelion. These factors combine to make this comet not only a target likely to have high public awareness, but also a particularly favorable candidate for close study to evaluate the behavior and evolution of comets near the Sun more generally. We propose to use WFC3/UVIS and ACS/WFC to collect multi-color imagery and imaging polarimetry of C/2020 F3 to trace the spatial variation of dust properties throughout the coma---particularly of its jets---and characterize or constrain the presence of fragments or unresolved debris streams produced by the earlier intense activity near perihelion. These observations will provide the first high resolution look at the effects of perihelic heating on a surviving near-Sun comet, and with the imminent loss of HST's three gyro mode and the corresponding collapse in its field of regard, will likely be the last opportunity of this favorability to conduct such analysis for the foreseeable future. ------------------------------------------------------------------------------------ Observations Description ------------------------ We request two orbits to conduct color imaging and polarimetry of C/2020 F3. As the comet will be receding from the Sun and the targeted activity rapidly declining during the observing window, the observations should be ideally scheduled as early as possible, once the comet leaves the 55 degree solar exclusion zone on 2020 August 3. Orbit 1 will use WFC3/UVIS to image the comet through five filters: F373N, F487N, F689M, F775W, and F845M. These filters were selected to minimize the contamination of dust colors by typical strong cometary emission lines. Two dithered frames will be collected through each filter to protect against passing field stars, cosmic rays, and detector defects. To avoid a serial buffer dump, the F487N, F689M, and F845M frames will be limited to a 1k subarray, which will provide a 40'' wide field of view---still sufficient to 16418( 12) - 20-Jul-2020 19:36:20 - [ 2] cover the inner coma. F373N and F775W will be recorded on the full UVIS frame in order to provide the widest possible field of view (2.7') to search for fragments. Orbit 2 will use ACS/WFC to image the comet through F775W crossed with each of the POL0V, POL60V, and POL120V polarizers. The limited ACS buffer size and inability to use <2k subarrays with polarizers limits this orbit to three dithered triplets of POL0V+POL60V+POL120V exposures. The first triplet will be comprised of very short exposures to avoid saturation, as described above, while the other two will be longer exposures to improve sensitivity to fainter structures and fragments. An unsaturated F775W+CLR exposure will also be included to protect the polarimetry of the near-nucleus region (likely saturated in the other two polarizer triplets) from stars, cosmic rays, and detector defects. We expect to measure polarizations in the range 10--40%, and with this exposure structure, we anticipate having sufficient S/N for the measured coma polarization to be calibration-limited over most of the frame. We additionally request coordinated parallel observations with ACS in orbit 1 and WFC3 in orbit 2. These observations will further constrain or characterize the presence of fragments away from the coma, as well any other spatially small features in the dust (including from the disintegration of unresolved fragments) that cannot be resolved from the ground as well as improve the precision of colors/polarimetry measured in the lower surface brightness outer regions of the coma by the primary observations, where sky background contamination could be important. ------------------------------------------------------------------------------------ 16418( 12) - 20-Jul-2020 19:36:20 - [ 3] TARGET LIST Solar System Targets ------------------------------------------------------------------------------------------------------------------------------------ TARGET NUMBER: 1 TARGET NAME: 2020F3 ------------------------------------------------------------------------------------------------------------------------------------ TARGET DESCRIPTION: COMET C/2020 F3 (NEOWISE) ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 1 TARGET POSITION LEVEL 2 TYPE=COMET, Q=0.2946512619109637, E=0.99916958479388, I=128.937400236612 , O=61.00942236569867, W=37.2784724513936, T=03-JUL-2020:16:17:50, TTimeScale=TDB, EQUINOX=J2000, EPOCH=03-AUG-2020:00:00:00, EpochTimeScale=TDB ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 3 WINDOWS ------------------------------------------------------------------------------------------------------------------------------------ DATA COMMENTS V = 6 Ephemeris Center: EARTH Extended: YES ------------------------------------------------------------------------------------------------------------------------------------ 16418( 12) - 20-Jul-2020 19:36:20 - [ 4] Visit: 01 Visit Requirements: 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| (Total) | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 2020F3 WFC3/UVI ACCUM UVIS2-M1K F487N 1 81 S (81 POS TARG 5.12, 5; GS ACQ S 1C-SUB S) SCENARIO ONEB1BE; PAR 4 WITH 1-3 ------------------------------------------------------------------------------------------------------------------------------------ 2 2020F3 WFC3/UVI ACCUM UVIS2-M1K F689M 1 12 S (12 SAME POS AS 1 S 1C-SUB S) ------------------------------------------------------------------------------------------------------------------------------------ 3 2020F3 WFC3/UVI ACCUM UVIS2-M1K F845M 1 20 S (20 SAME POS AS 1 S 1C-SUB S) ------------------------------------------------------------------------------------------------------------------------------------ 4 2020F3 ACS/WFC ACCUM WFC F775W, 1 240 S (240 POL120V S) ------------------------------------------------------------------------------------------------------------------------------------ 5 2020F3 WFC3/UVI ACCUM UVIS2-M1K F845M 1 20 S (20 POS TARG 5.12, 5; PAR 8 S 1C-SUB S) WITH 5-7 ------------------------------------------------------------------------------------------------------------------------------------ 6 2020F3 WFC3/UVI ACCUM UVIS2-M1K F689M 1 11 S (11 SAME POS AS 5 S 1C-SUB S) ------------------------------------------------------------------------------------------------------------------------------------ 7 2020F3 WFC3/UVI ACCUM UVIS2-M1K F487N 1 81 S (81 SAME POS AS 5 S 1C-SUB S) ------------------------------------------------------------------------------------------------------------------------------------ 8 2020F3 ACS/WFC ACCUM WFC F775W, 1 289 S (289 POL60V S) ------------------------------------------------------------------------------------------------------------------------------------ 9 2020F3 WFC3/UVI ACCUM UVIS-CENT F775W 1 232 S (232 POS TARG 5, -15; PAR S ER S) 11-12 WITH 9-10 ------------------------------------------------------------------------------------------------------------------------------------ 10 2020F3 WFC3/UVI ACCUM UVIS-FIX F373N FLASH=5 1 348 S (348 SAME POS AS 9 S S) ------------------------------------------------------------------------------------------------------------------------------------ 11 2020F3 ACS/WFC ACCUM WFC F775W, 1 387 S (387 POL0V S) ------------------------------------------------------------------------------------------------------------------------------------ 12 2020F3 ACS/WFC ACCUM WFC F775W, 1 181 S (181 POL0V S) ------------------------------------------------------------------------------------------------------------------------------------ 13 2020F3 WFC3/UVI ACCUM UVIS-CENT F373N FLASH=5 1 348 S (348 POS TARG 5.12, -17; PAR S ER S) 15-16 WITH 13-14 ------------------------------------------------------------------------------------------------------------------------------------ 14 2020F3 WFC3/UVI ACCUM UVIS-FIX F775W 1 232 S (232 SAME POS AS 13 S S) 16418( 12) - 20-Jul-2020 19:36:20 - [ 5] Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exp | Target | Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Num | Name | Config | Mode | or FOV |Element |Waveln.| Parameters |Exp| (Total) | Requirements ------------------------------------------------------------------------------------------------------------------------------------ ------------------------------------------------------------------------------------------------------------------------------------ 15 2020F3 ACS/WFC ACCUM WFC F775W, 1 258 S (258 POL60V S) ------------------------------------------------------------------------------------------------------------------------------------ 16 2020F3 ACS/WFC ACCUM WFC F775W, 1 288 S (288 POL120V S) ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ 2020F3 1 WFC3/UVI ACCUM UVIS2-M1 F487N none none none none 1 N/A S K1C-SUB 2020F3 2 WFC3/UVI ACCUM UVIS2-M1 F689M none none none none 1 N/A S K1C-SUB 2020F3 3 WFC3/UVI ACCUM UVIS2-M1 F845M none none none none 1 N/A S K1C-SUB 2020F3 4 ACS/WFC ACCUM WFC F775W, none none none none 1 N/A POL120V 2020F3 5 WFC3/UVI ACCUM UVIS2-M1 F845M none none none none 1 N/A S K1C-SUB 2020F3 6 WFC3/UVI ACCUM UVIS2-M1 F689M none none none none 1 N/A S K1C-SUB 2020F3 7 WFC3/UVI ACCUM UVIS2-M1 F487N none none none none 1 N/A S K1C-SUB 2020F3 8 ACS/WFC ACCUM WFC F775W, none none none none 1 N/A POL60V 2020F3 9 WFC3/UVI ACCUM UVIS-CEN F775W none none none none 1 N/A S TER 2020F3 10 WFC3/UVI ACCUM UVIS-FIX F373N none none none none 1 N/A S 2020F3 11 ACS/WFC ACCUM WFC F775W, none none none none 1 N/A POL0V 2020F3 12 ACS/WFC ACCUM WFC F775W, none none none none 1 N/A POL0V 2020F3 13 WFC3/UVI ACCUM UVIS-CEN F373N none none none none 1 N/A S TER 2020F3 14 WFC3/UVI ACCUM UVIS-FIX F775W none none none none 1 N/A S 2020F3 15 ACS/WFC ACCUM WFC F775W, none none none none 1 N/A POL60V 2020F3 16 ACS/WFC ACCUM WFC F775W, none none none none 1 N/A POL120V 16418( 12) - 20-Jul-2020 19:36:20 - [ 6] Visit: 02 Visit Requirements: GROUP 02, 01 WITHIN 5.2 Orbits 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| (Total) | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 2020F3 ACS/WFC ACCUM WFC1B-2K F775W 1 3 S (3 S) POS TARG 2, -2; GS ACQ SCENARIO ONEB1BE; PAR 5-6 WITH 1-4 ------------------------------------------------------------------------------------------------------------------------------------ 2 2020F3 ACS/WFC ACCUM WFC F775W, 1 10 S (10 SAME POS AS 1 POL0V S) ------------------------------------------------------------------------------------------------------------------------------------ 3 2020F3 ACS/WFC ACCUM WFC F775W, 1 10 S (10 SAME POS AS 1 POL60V S) ------------------------------------------------------------------------------------------------------------------------------------ 4 2020F3 ACS/WFC ACCUM WFC F775W, 1 10 S (10 SAME POS AS 1 POL120V S) ------------------------------------------------------------------------------------------------------------------------------------ 5 2020F3 WFC3/UVI ACCUM UVIS1-2K2 F373N FLASH=10 1 197 S (197 S A-SUB S) ------------------------------------------------------------------------------------------------------------------------------------ 6 2020F3 WFC3/UVI ACCUM UVIS1-2K2 F373N FLASH=10 1 196 S (196 S A-SUB S) ------------------------------------------------------------------------------------------------------------------------------------ 7 2020F3 ACS/WFC ACCUM WFC F775W, 1 150 S (150 POS TARG 0, -2; PAR POL120V S) 10-12 WITH 7-9 ------------------------------------------------------------------------------------------------------------------------------------ 8 2020F3 ACS/WFC ACCUM WFC F775W, 1 150 S (150 SAME POS AS 7 POL60V S) ------------------------------------------------------------------------------------------------------------------------------------ 9 2020F3 ACS/WFC ACCUM WFC F775W, 1 150 S (150 SAME POS AS 7 POL0V S) ------------------------------------------------------------------------------------------------------------------------------------ 10 2020F3 WFC3/UVI ACCUM UVIS1-2K2 F775W 1 110 S (110 S A-SUB S) ------------------------------------------------------------------------------------------------------------------------------------ 11 2020F3 WFC3/UVI ACCUM UVIS1-2K2 F775W 1 110 S (110 S A-SUB S) ------------------------------------------------------------------------------------------------------------------------------------ 12 2020F3 WFC3/UVI ACCUM UVIS1-2K2 F775W 1 110 S (110 S A-SUB S) ------------------------------------------------------------------------------------------------------------------------------------ 13 2020F3 ACS/WFC ACCUM WFC F775W, 1 56 S (56 PAR 16-17 WITH 13-15 POL0V S) ------------------------------------------------------------------------------------------------------------------------------------ 14 2020F3 ACS/WFC ACCUM WFC F775W, 1 56 S (56 SAME POS AS 13 POL60V S) 16418( 12) - 20-Jul-2020 19:36:20 - [ 7] Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exp | Target | Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Num | Name | Config | Mode | or FOV |Element |Waveln.| Parameters |Exp| (Total) | Requirements ------------------------------------------------------------------------------------------------------------------------------------ ------------------------------------------------------------------------------------------------------------------------------------ 15 2020F3 ACS/WFC ACCUM WFC F775W, 1 56 S (56 SAME POS AS 13 POL120V S) ------------------------------------------------------------------------------------------------------------------------------------ 16 2020F3 WFC3/UVI ACCUM UVIS F775W 1 270 S (270 S S) ------------------------------------------------------------------------------------------------------------------------------------ 17 2020F3 WFC3/UVI ACCUM UVIS F775W 1 103 S (103 S S) ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ 2020F3 1 ACS/WFC ACCUM WFC1B-2K F775W none none none none 1 N/A 2020F3 2 ACS/WFC ACCUM WFC F775W, none none none none 1 N/A POL0V 2020F3 3 ACS/WFC ACCUM WFC F775W, none none none none 1 N/A POL60V 2020F3 4 ACS/WFC ACCUM WFC F775W, none none none none 1 N/A POL120V 2020F3 5 WFC3/UVI ACCUM UVIS1-2K F373N none none none none 1 N/A S 2A-SUB 2020F3 6 WFC3/UVI ACCUM UVIS1-2K F373N none none none none 1 N/A S 2A-SUB 2020F3 7 ACS/WFC ACCUM WFC F775W, none none none none 1 N/A POL120V 2020F3 8 ACS/WFC ACCUM WFC F775W, none none none none 1 N/A POL60V 2020F3 9 ACS/WFC ACCUM WFC F775W, none none none none 1 N/A POL0V 2020F3 10 WFC3/UVI ACCUM UVIS1-2K F775W none none none none 1 N/A S 2A-SUB 2020F3 11 WFC3/UVI ACCUM UVIS1-2K F775W none none none none 1 N/A S 2A-SUB 2020F3 12 WFC3/UVI ACCUM UVIS1-2K F775W none none none none 1 N/A S 2A-SUB 2020F3 13 ACS/WFC ACCUM WFC F775W, none none none none 1 N/A POL0V 2020F3 14 ACS/WFC ACCUM WFC F775W, none none none none 1 N/A POL60V 2020F3 15 ACS/WFC ACCUM WFC F775W, none none none none 1 N/A POL120V 2020F3 16 WFC3/UVI ACCUM UVIS F775W none none none none 1 N/A S 16418( 12) - 20-Jul-2020 19:36:20 - [ 8] 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 | ------------------------------------------------------------------------------------------------------------------------------------ 2020F3 17 WFC3/UVI ACCUM UVIS F775W none none none none 1 N/A S 16418( 12) - 20-Jul-2020 19:36:20 - [ 9] Summary Form for Proposal 16418 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures UVIS, UVIS-CENTER, UVIS-FIX, UVIS1-2K2A-SUB, UVIS2-M1K1C-SUB, WFC, WFC1B-2K ------------------------------------------------------------------------------------------------------------------------------------ Configurations ACS/WFC, WFC3/UVIS ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters FLASH=10, FLASH=5 ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements GROUP 02, 01 WITHIN 5.2 Orbits, GS ACQ SCENARIO ONEB1BE, PAR 10-12 WITH 7-9, PAR 11-12 WITH 9-10, PAR 15-16 WITH 13-14, PAR 16-17 WITH 13-15, PAR 4 WITH 1-3, PAR 5-6 WITH 1-4, PAR 8 WITH 5-7, POS TARG 0, -2, POS TARG 2, -2, POS TARG 5, -15, POS TARG 5.12, -17, POS TARG 5.12, 5, SAME POS AS 1, SAME POS AS 13, SAME POS AS 5, SAME POS AS 7, SAME POS AS 9 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F373N, F487N, F689M, F775W, F845M, POL0V, POL120V, POL60V ------------------------------------------------------------------------------------------------------------------------------------ Target Names 2020F3 ------------------------------------------------------------------------------------------------------------------------------------