15406( 15) - 01-Feb-2018 16:46:10 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 15406 Version: 15 Check-in Time: 01-Feb-2018 16:46:10 STScI Edit Number: 0 Title Cause and characteristics of the major outburst of comet C/2017 O1 (ASASSN) ------------------------------------------------------------------------------------ Type Cycle GO/DD 25 ------------------------------------------------------------------------------------ Investigators Contact? PI: Dr. Karen J. Meech University of Hawaii Y CoI: Prof. Benjamin John Shappee University of Hawaii N CoI: Dr. Larry Denneau University of Hawaii N CoI: Dr. James M. Bauer University of Maryland N CoI: Dr. Olivier Hainaut European Southern Observatory - Germany N CoI: Marco Micheli ESA SSA-NEO Coordination Centre N CoI: Dr. Jan Kleyna University of Hawaii N CoI: Dr. Jacqueline Keane University of Hawaii N CoI: Dr. Bin Yang European Southern Observatory - Chile N CoI: Dr. Harald Ebeling University of Hawaii N ------------------------------------------------------------------------------------ Abstract We seek to observe comet C/2017 O1 (ASASSN), which remained undetected even at a distance from the Sun of only a few a.u., but is currently undergoing a major outburst (dm~5). We aim to search for near-nucleus fragments and, if they are present, determine their size distribution down to <10m, investigate the total mass of ejected material, and identify the cause of the outburst by measuring fragment velocities and searching for color variations among the fragments. C/2017 O1 provides a unique opportunity to collect observational evidence of the origins and evolution of comets, as only a handful of long-period comets that have had outbursts this large have been studied in detail. We propose a single-orbit observation in November to establish whether fragmentation occurred; only if fragments are detected, we request two additional single-orbit observations in intervals of a few days to determine the fragments' velocity and evolution. Should fragments be found to move too slowly to allow velocity determinations from the resulting dataset, we request a final set of two 1-orbit visits in February 2018 when the fragments' separation has increased. Regardless of whether splitting occurred or not, the requested observations will allow us to explore the inner coma for any structures or jets that could reveal the physical mechanism behind the outburst, thus adding an important datapoint to a currently still very small sample of well studied cometary outbursts. As such, the proposed project will provide fresh insights into a class of objects that are central to our understanding of the physical and chemical evolution of the solar system. ------------------------------------------------------------------------------------ Observations Description ------------------------ This single-orbit observation is meant to establish whether fragmentation is the cause of the outburst and to search for differences in color between any 15406( 15) - 01-Feb-2018 16:46:10 - [ 2] fragments, if present. If fragments are detected, two additional visits will be requested in order to measure the fragments' velocities. The present observation is designed to (a) detect the nucleus as well as any fragments, using the high throughput of the F350LP filter and the excellent angular resolution of WFC3/UVIS, and (b) to explore the presence of color variations by obtaining photometry in a much redder, high-throughput bandpass, namely the F110W filter in the WFC3/IR channel. Both parts of this exploration take about approximately equal parts of this single-orbit observation; dithering is applied to the extent allowed by the constraints set by the need to dump buffers. The sole visit of this observation needs to be scheduled within the Nov 29 - Dec 3, 2017 window within which projection effects are minimal, thereby allowing fragments to be detected if present. The optimal time within this window, determined by the requirement that a sufficient number of reference stars (and no bright stars) fall within the field of view, is still under investigation. ------------------------------------------------------------------------------------ 15406( 15) - 01-Feb-2018 16:46:10 - [ 3] TARGET LIST Solar System Targets ------------------------------------------------------------------------------------------------------------------------------------ TARGET NUMBER: 1 TARGET NAME: C2017-O1 ------------------------------------------------------------------------------------------------------------------------------------ TARGET DESCRIPTION: COMET Comet undergoing major outburst, possibly due to fragmentation ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 1 TARGET POSITION LEVEL 2 TYPE=COMET, Q=1.49871313, E=0.9965450, I=39.84913, O=25.81029, W=20.90731, T=14-OCT-2017:18:49:20, TTimeScale=UTC, EQUINOX=J2000, EPOCH=01-NOV-2017:00:00:00, EpochTimeScale=UTC, A1=0, A2=0, A3=0 ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 3 WINDOWS ------------------------------------------------------------------------------------------------------------------------------------ DATA COMMENTS V = 27.3 Ephemeris Center: EARTH ------------------------------------------------------------------------------------------------------------------------------------ 15406( 15) - 01-Feb-2018 16:46:10 - [ 4] Patterns ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 1 Primary_Pattern Secondary_Pattern Pattern_Type WFC3-UVIS-DITHER-LINE-3PT Pattern_Purpose DITHER Number_Of_Points 3 Point_Spacing 0.135 Line_Spacing Coordinate_Frame POS-TARG Pattern_Orient 46.84 Angle_Between_Sides Center_Pattern NO Pattern_Comments: This is a small fractional pixel dither for non-redundant pixels between frames on the target. ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 3 Primary_Pattern Secondary_Pattern Pattern_Type WFC3-IR-DITHER-BOX-MIN Pattern_Purpose DITHER Number_Of_Points 4 Point_Spacing 0.572 Line_Spacing 0.365 Coordinate_Frame POS-TARG Pattern_Orient 18.528 Angle_Between_Sides 74.653 Center_Pattern NO ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 4 Primary_Pattern Secondary_Pattern Pattern_Type WFC3-IR-DITHER-BLOB WFC3-IR-DITHER-BOX-MIN Pattern_Purpose DITHER DITHER Number_Of_Points 2 4 Point_Spacing 5.183 0.572 Line_Spacing 0.365 Coordinate_Frame POS-TARG POS-TARG Pattern_Orient 41.859 18.528 Angle_Between_Sides 74.653 Center_Pattern YES NO ------------------------------------------------------------------------------------------------------------------------------------ 15406( 15) - 01-Feb-2018 16:46:10 - [ 5] Patterns ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 5 Primary_Pattern Secondary_Pattern Pattern_Type WFC3-UVIS-GAP-LINE WFC3-UVIS-DITHER-LINE Pattern_Purpose MOSAIC DITHER Number_Of_Points 2 2 Point_Spacing 2.414 0.145 Line_Spacing Coordinate_Frame POS-TARG POS-TARG Pattern_Orient 85.759 46.84 Angle_Between_Sides Center_Pattern YES NO ------------------------------------------------------------------------------------------------------------------------------------ 15406( 15) - 01-Feb-2018 16:46:10 - [ 6] Visit: 01 (Visit 1) Visit Requirements: BETWEEN 29-NOV-2017:00:00:00 AND 03-DEC-2017:00:00:00 On Hold Comments: Additional Comments: We request scheduling of this observation in the 2017.335:00:16:14 slot. 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 C2017-O1 WFC3/IR MULTIAC IR-UVIS F110W SAMP-SEQ=SPARS25, NSAMP=10 1 DEF POS TARG null, 45; SEQ 1 CUM (911.748 NON-INT; PATTERN 3 1 S) ------------------------------------------------------------------------------------------------------------------------------------ 2 C2017-O1 WFC3/UVI ACCUM UVIS1 F350LP 1 349 S SEQ 2 NON-INT; PATTERN 1 S see below 2 (1116 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 | ------------------------------------------------------------------------------------------------------------------------------------ C2017-O1 1 WFC3/IR MULTIAC IR-UVIS F110W 1 none none none 1 N/A CUM C2017-O1 1 WFC3/IR MULTIAC IR-UVIS F110W 2 none none none 1 N/A CUM C2017-O1 1 WFC3/IR MULTIAC IR-UVIS F110W 3 none none none 1 N/A CUM C2017-O1 1 WFC3/IR MULTIAC IR-UVIS F110W 4 none none none 1 N/A CUM C2017-O1 2 WFC3/UVI ACCUM UVIS1 F350LP 1 none none none 1 372.0 S S C2017-O1 2 WFC3/UVI ACCUM UVIS1 F350LP 2 none none none 1 372.0 S S C2017-O1 2 WFC3/UVI ACCUM UVIS1 F350LP 3 none none none 1 372.0 S S 15406( 15) - 01-Feb-2018 16:46:10 - [ 7] Visit: 02 (IR-F110W) Visit Requirements: ORIENT 90D TO 91 D; BETWEEN 12-FEB-2018:00:00:00 AND 18-FEB-2018:00:00:00 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| (Total) | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 C2017-O1 WFC3/IR MULTIAC IR-UVIS-C F110W SAMP-SEQ=SPARS25, NSAMP=12 1 DEF POS TARG -45, null; SEQ CUM ENTER (2223.504 1 NON-INT; PATTERN 4 1 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 | ------------------------------------------------------------------------------------------------------------------------------------ C2017-O1 1 WFC3/IR MULTIAC IR-UVIS- F110W 1 1 none none 1 N/A CUM CENTER C2017-O1 1 WFC3/IR MULTIAC IR-UVIS- F110W 1 2 none none 1 N/A CUM CENTER C2017-O1 1 WFC3/IR MULTIAC IR-UVIS- F110W 1 3 none none 1 N/A CUM CENTER C2017-O1 1 WFC3/IR MULTIAC IR-UVIS- F110W 1 4 none none 1 N/A CUM CENTER C2017-O1 1 WFC3/IR MULTIAC IR-UVIS- F110W 2 1 none none 1 N/A CUM CENTER C2017-O1 1 WFC3/IR MULTIAC IR-UVIS- F110W 2 2 none none 1 N/A CUM CENTER C2017-O1 1 WFC3/IR MULTIAC IR-UVIS- F110W 2 3 none none 1 N/A CUM CENTER C2017-O1 1 WFC3/IR MULTIAC IR-UVIS- F110W 2 4 none none 1 N/A CUM CENTER 15406( 15) - 01-Feb-2018 16:46:10 - [ 8] Visit: 03 (UVIS-F350LP) Visit Requirements: SAME ORIENT AS 02 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 C2017-O1 WFC3/UVI ACCUM UVIS-CENT F350LP CR-SPLIT=NO 1 409 S POS TARG -45, 5; GS ACQ S ER (1636 S) SCENARIO BASE1B3; SEQ 1-2 NON-INT; PATTERN 5 1 ------------------------------------------------------------------------------------------------------------------------------------ 2 C2017-O1 WFC3/UVI ACCUM UVIS-CENT F350LP 1 409 S (409 POS TARG -45, 5 S ER 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 | ------------------------------------------------------------------------------------------------------------------------------------ C2017-O1 1 WFC3/UVI ACCUM UVIS-CEN F350LP 1 1 none none 1 N/A S TER C2017-O1 1 WFC3/UVI ACCUM UVIS-CEN F350LP 1 2 none none 1 N/A S TER C2017-O1 1 WFC3/UVI ACCUM UVIS-CEN F350LP 2 1 none none 1 N/A S TER C2017-O1 1 WFC3/UVI ACCUM UVIS-CEN F350LP 2 2 none none 1 N/A S TER C2017-O1 2 WFC3/UVI ACCUM UVIS-CEN F350LP none none none none 1 N/A S TER 15406( 15) - 01-Feb-2018 16:46:10 - [ 9] Summary Form for Proposal 15406 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures IR-UVIS, IR-UVIS-CENTER, UVIS-CENTER, UVIS1 ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFC3/IR, WFC3/UVIS ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM, MULTIACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters CR-SPLIT=NO, NSAMP=10, NSAMP=12, SAMP-SEQ=SPARS25 ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements BETWEEN 12-FEB-2018:00:00:00 AND 18-FEB-2018:00:00:00, BETWEEN 29-NOV-2017:00:00:00 AND 03-DEC-2017:00:00:00, GS ACQ SCENARIO BASE1B3, ORIENT 90D TO 91 D, PATTERN 1 2, PATTERN 3 1, PATTERN 4 1, PATTERN 5 1, POS TARG -45, 5, POS TARG -45, null, POS TARG null, 45, SAME ORIENT AS 02, SEQ 1 NON-INT, SEQ 1-2 NON-INT, SEQ 2 NON-INT ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F110W, F350LP ------------------------------------------------------------------------------------------------------------------------------------ Target Names C2017-O1 ------------------------------------------------------------------------------------------------------------------------------------