17254( 7) - 19-Oct-2022 13:56:26 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 17254 Version: 7 Check-in Time: 19-Oct-2022 13:56:26 STScI Edit Number: 1 Title Determining the Driver of Activity in a Newly Discovered Main Belt Comet ------------------------------------------------------------------------------------ Type Cycle GO/DD 30 ------------------------------------------------------------------------------------ Investigators Contact? PI: Dr. Jacqueline Keane University of Hawaii Y CoI: Dr. Karen J. Meech University of Hawaii N CoI: Dr. Robert Weryk University of Hawaii N CoI: Dr. Richard Wainscoat University of Hawaii N CoI: Dr. Jan Kleyna University of Hawaii N ------------------------------------------------------------------------------------ Abstract On 2022 September 8, Pan-STARRS detected a dust tail / trail associated with a new main-belt asteroid candidate. Confirming follow-up observations with the 3.6m Canada-France-Hawaii Telescope on September 22 show a tail corresponding to at least 25, 000 km length in space. A search of the Pan-STARRS image archive shows no matching object in pre-discovery images, nor could the recent astrometry be linked to any existing asteroid, or isolated tracklets, implying that this is a new discovery that was not previously visible. Something happened recently to trigger significant activity, resulting in an increase in brightness by at least 2 orders of magnitude. We propose a DD programme of WFC3 imaging over two orbits. Only HST will allow us to study the changing morphology of the dust structures and thus differentiate between continuous mass-loss and an impulsive event. ------------------------------------------------------------------------------------ Observations Description ------------------------ Optical imaging observations to explore the dust surrounding an active asteroid. We request a total time baseline for observations of approximately two months, with visits spaced roughly equally, to enable robust measurements of the evolution of the dust structure and of the velocity of any detected fragments. While we would like to observe the asteroid as soon as possible, disruptive scheduling is not warranted. Our basic observing strategy is to take multiple long exposures using WFC3 and the F350LP wide bandpass filter. ------------------------------------------------------------------------------------ 17254( 7) - 19-Oct-2022 13:56:26 - [ 2] TARGET LIST Solar System Targets ------------------------------------------------------------------------------------------------------------------------------------ TARGET NUMBER: 1 TARGET NAME: P21XDAC ------------------------------------------------------------------------------------------------------------------------------------ TARGET DESCRIPTION: ASTEROID Active asteroid in the main asteroid belt. ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 1 TARGET POSITION LEVEL 2 TYPE=ASTEROID, A=3.0705665, E= 0.1956716, I=15.29185, O=115.06373, W=240.71338, M=23.81960201, EQUINOX=J2000, EPOCH=05-OCT-2022:00:00:00, EpochTimeScale=UTC ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 3 WINDOWS ------------------------------------------------------------------------------------------------------------------------------------ DATA COMMENTS V = 27 +/- 6 Ephemeris Center: EARTH Extended: NO ------------------------------------------------------------------------------------------------------------------------------------ TARGET NUMBER: 2 TARGET NAME: P21XDAC2 ------------------------------------------------------------------------------------------------------------------------------------ TARGET DESCRIPTION: ASTEROID asteroid ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 1 TARGET POSITION LEVEL 2 TYPE=ASTEROID, A=3.070266776415772, E=0.1955671799352209, I=15.29187909037629 , O=115.062336313636, W=240.7237704225099, M=21.80331790047074, EQUINOX=J2000, EPOCH=24-SEP-2022:00:00:00, EpochTimeScale=TDB ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 3 WINDOWS ------------------------------------------------------------------------------------------------------------------------------------ DATA COMMENTS V = 26 +/- 6 Ephemeris Center: EARTH ------------------------------------------------------------------------------------------------------------------------------------ 17254( 7) - 19-Oct-2022 13:56:26 - [ 3] Patterns ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 1 Primary_Pattern Secondary_Pattern Pattern_Type WFC3-UVIS-DITHER-LINE Pattern_Purpose DITHER Number_Of_Points 2 Point_Spacing 0.145 Line_Spacing Coordinate_Frame POS-TARG Pattern_Orient 46.84 Angle_Between_Sides Center_Pattern NO ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 2 Primary_Pattern Secondary_Pattern Pattern_Type WFC3-UVIS-DITHER-BOX Pattern_Purpose DITHER Number_Of_Points 4 Point_Spacing 0.173 Line_Spacing 0.112 Coordinate_Frame POS-TARG Pattern_Orient 23.884 Angle_Between_Sides 81.785 Center_Pattern NO ------------------------------------------------------------------------------------------------------------------------------------ 17254( 7) - 19-Oct-2022 13:56:26 - [ 4] Visit: 01 Visit Requirements: BETWEEN 17-OCT-2022:00:00:00 AND 18-OCT-2022:03:00:00; BETWEEN 18-OCT-2022:13:00:00 AND 24-OCT-2022:00:00:00; VISIBILITY INTERVAL NO GYRO BIAS UPDATE ON MOVING TARGET 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 P21XDAC WFC3/UVI ACCUM UVIS2-2K2 F350LP CR-SPLIT=NO 3 245 S SEQ 1 NON-INT; PATTERN 1 S C-SUB (1470 S) 1 ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ P21XDAC 1 WFC3/UVI ACCUM UVIS2-2K F350LP 1 none 1 none 1 N/A S 2C-SUB P21XDAC 1 WFC3/UVI ACCUM UVIS2-2K F350LP 1 none 2 none 1 N/A S 2C-SUB P21XDAC 1 WFC3/UVI ACCUM UVIS2-2K F350LP 1 none 3 none 1 N/A S 2C-SUB P21XDAC 1 WFC3/UVI ACCUM UVIS2-2K F350LP 2 none 1 none 1 N/A S 2C-SUB P21XDAC 1 WFC3/UVI ACCUM UVIS2-2K F350LP 2 none 2 none 1 N/A S 2C-SUB P21XDAC 1 WFC3/UVI ACCUM UVIS2-2K F350LP 2 none 3 none 1 N/A S 2C-SUB 17254( 7) - 19-Oct-2022 13:56:26 - [ 5] Visit: 02 Visit Requirements: AFTER 01 BY 21 D TO 45 D; BETWEEN 12-NOV-2022:00:00:00 AND 12-NOV-2022:00:30:00; BETWEEN 12-NOV-2022:02:30:00 AND 12-NOV-2022:06:30:00; BETWEEN 12-NOV-2022:11:00:00 AND 12-NOV-2022:13:45:00; BETWEEN 12-NOV-2022:17:00:00 AND 13-NOV-2022:00:30:00; BETWEEN 13-NOV-2022:02:30:00 AND 13-NOV-2022:04:00:00; BETWEEN 13-NOV-2022:05:30:00 AND 13-NOV-2022:07:00:00; BETWEEN 13-NOV-2022:11:00:00 AND 13-NOV-2022:16:00:00; BETWEEN 13-NOV-2022:23:00:00 AND 14-NOV-2022:21:30:00; VISIBILITY INTERVAL NO GYRO BIAS UPDATE ON MOVING TARGET 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 P21XDAC2 WFC3/UVI ACCUM UVIS2-2K2 F350LP CR-SPLIT=NO 3 245 S SEQ 1 NON-INT; PATTERN 1 S C-SUB (1470 S) 1 ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ P21XDAC2 1 WFC3/UVI ACCUM UVIS2-2K F350LP 1 none 1 none 1 N/A S 2C-SUB P21XDAC2 1 WFC3/UVI ACCUM UVIS2-2K F350LP 1 none 2 none 1 N/A S 2C-SUB P21XDAC2 1 WFC3/UVI ACCUM UVIS2-2K F350LP 1 none 3 none 1 N/A S 2C-SUB P21XDAC2 1 WFC3/UVI ACCUM UVIS2-2K F350LP 2 none 1 none 1 N/A S 2C-SUB P21XDAC2 1 WFC3/UVI ACCUM UVIS2-2K F350LP 2 none 2 none 1 N/A S 2C-SUB P21XDAC2 1 WFC3/UVI ACCUM UVIS2-2K F350LP 2 none 3 none 1 N/A S 2C-SUB 17254( 7) - 19-Oct-2022 13:56:26 - [ 6] Summary Form for Proposal 17254 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures UVIS2-2K2C-SUB ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFC3/UVIS ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters CR-SPLIT=NO ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements AFTER 01 BY 21 D TO 45 D, BETWEEN 12-NOV-2022:00:00:00 AND 12-NOV-2022:00:30:00, BETWEEN 12-NOV-2022:02:30:00 AND 12-NOV-2022:06:30:00, BETWEEN 12-NOV-2022:11:00:00 AND 12-NOV-2022:13:45:00, BETWEEN 12-NOV-2022:17:00:00 AND 13-NOV-2022:00:30:00, BETWEEN 13-NOV-2022:02:30:00 AND 13-NOV-2022:04:00:00, BETWEEN 13-NOV-2022:05:30:00 AND 13-NOV-2022:07:00:00, BETWEEN 13-NOV-2022:11:00:00 AND 13-NOV-2022:16:00:00, BETWEEN 13-NOV-2022:23:00:00 AND 14-NOV-2022:21:30:00, BETWEEN 17-OCT-2022:00:00:00 AND 18-OCT-2022:03:00:00, BETWEEN 18-OCT-2022:13:00:00 AND 24-OCT-2022:00:00:00, PATTERN 1 1, SEQ 1 NON-INT, VISIBILITY INTERVAL NO GYRO BIAS UPDATE ON MOVING TARGET ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F350LP ------------------------------------------------------------------------------------------------------------------------------------ Target Names P21XDAC, P21XDAC2 ------------------------------------------------------------------------------------------------------------------------------------