15481( 4) - 15-Apr-2019 13:25:31 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 15481 Version: 4 Check-in Time: 15-Apr-2019 13:25:31 STScI Edit Number: 0 Title The orbital evolution of binary main-belt comet 288P/300163 ------------------------------------------------------------------------------------ Type Cycle GO 25 ------------------------------------------------------------------------------------ Investigators Contact? PI: Dr. Jessica Agarwal Max Planck Institute for Solar System Y Research CoI: Dr. David Jewitt University of California - Los Angeles N CoI: Dr. Harold A. Weaver The Johns Hopkins University Applied N Physics Laboratory CoI: Max Mutchler Space Telescope Science Institute N CoI: Dr. Stephen M. Larson University of Arizona N ------------------------------------------------------------------------------------ Abstract We request 5 orbits of mid-cycle time, spaced at 50-day intervals between 2018, November and 2019, June, to continue studying the orbital evolution of the unique binary main-belt comet 288P/300163. HST/WFC3 observations from 2016/17 revealed that 288P is unusual due to its combination of nearly equal component size, wide separation, high eccentricity, and sublimation-driven activity. Possible formation scenarios include a collision, rotational break-up or a combination of both. The interrelation of activity and orbital evolution seems probable but is highly model-dependent and unconfirmed. In data from 2017/18, we find indications of a change of the orbital elements during the past year, which has significant consequences for modelling the past and future evolution of the system. We request renewed observations of 288P to investigate if the orbit change was induced by the several months of activity in 2016/17, or if the orbit keeps changing also without activity. In order to link the new data to those from previous arcs, the observations should start as soon as possible when 288P emerges from HST's solar exclusion zone in late October 2018, which is why we request mid-cycle time. ------------------------------------------------------------------------------------ Observations Description ------------------------ The goal of the observations is to repeatedly measure the projected component separation of the binary asteroid 288P in order to derive the orbital elements of the binary system during Cycle 26. Five visits are the minimum requirement to contrain the orbital elements, assuming that the binary and heliocentric orbital planes are parallel. We propose to observe the 288P system during 5 epochs in ~50-day intervals during the visibility period between 2018 October and 2019 June. The timing of each visit is flexible within +/-1 week. All five orbits will be suited to measure the absolute magnitude of the components and its rotational variability. We expect each component to have V~23, and component separations up to 0.03 arcsec. We will employ a subsampling dither box pattern combined with careful PSF-fitting to measure the sub-pixel component separations. 15481( 4) - 15-Apr-2019 13:25:31 - [ 2] In each orbit, we will take 8 exposures of ~225s using the 1k subarray of WFC3 and perform a subsampling dither box pattern, obtaining 2 exposures at each dither point. The orbital visibility for a solar system target near the ecliptic plane is 54 min (Section 6.3 of the HST Primer document). The described strategy provides a total exposure time of 1800s = 30 min, and estimated overheads of 6 min for guide-star acquisition, 2.6 min for the first exposure, a total of 14.7 min for the subsequent 7 exposures, and 1.5 min for the three spacecraft maneuvers required for dithering, which adds up to a total execution time of 54 min per orbit. This dither strategy is identical to the one employed successfully for this target during Cycles 24 and 25, ensuring maximum comparability of the data. We will use the wide bandpass filter F606W for an optimum trade-off between sensitivity and highest resolution: the bandpass (475 - 700 nm) covers the maximum of the solar spectrum, and is in the wavelength range where the PSF is smallest (FWHM<0.07 arcsec, from the WFC3 Instrument Handbook for Cycle 25), such that we can optimally exploit our subsampling dither strategy. In addition, F606W is the same filter we used to observe 288P in GO 12597, 14790, 14864, 14884, and 15328, enabling a direct comparison of the data sets. The WFC3 exposure time calculator returns for a solar-spectrum point source at V=22.3 (combined for both components), exposure time of 450 s, F606W filter, and default background values a signal-to-noise-ratio of 105 within a circle of 0.2 arcsec (ETC Request ID: WFC3UVIS.im.1154717). This signal will be sufficient to reliably fit the PSFs. ------------------------------------------------------------------------------------ 15481( 4) - 15-Apr-2019 13:25:31 - [ 3] TARGET LIST Solar System Targets ------------------------------------------------------------------------------------------------------------------------------------ TARGET NUMBER: 1 TARGET NAME: 288P ------------------------------------------------------------------------------------------------------------------------------------ TARGET DESCRIPTION: COMET COMET 288P, ASTEROID 300163 ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 1 TARGET POSITION LEVEL 2 TYPE=COMET, Q=2.434091859832713, E=0.2011952883437459, I=3.240682641168021, O=83.19068811025544, W=281.2529259614446, T=08-NOV-2016:21:17:35, TTimeScale=TDB, EQUINOX=J2000, EPOCH=29-APR-2014:00:00:00, EpochTimeScale=TDB ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 3 WINDOWS ------------------------------------------------------------------------------------------------------------------------------------ DATA COMMENTS V = 22.3 +/- 0.1 Ephemeris Center: EARTH Extended: NO ------------------------------------------------------------------------------------------------------------------------------------ 15481( 4) - 15-Apr-2019 13:25:31 - [ 4] Patterns ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 1 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 ------------------------------------------------------------------------------------------------------------------------------------ 15481( 4) - 15-Apr-2019 13:25:31 - [ 5] Visit: 01 Visit Requirements: BETWEEN 01-NOV-2018:00:00:00 AND 15-NOV-2018:00:00:00 On Hold Comments: Additional Comments: The flash warning disappears when using the zodiacal light model for the actual position of the target close to the ecliptic. 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 288P WFC3/UVI ACCUM UVIS2-C1K F606W CR-SPLIT=NO 2 230 S PATTERN 1 1 S 1C-SUB (1840 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 | ------------------------------------------------------------------------------------------------------------------------------------ 288P 1 WFC3/UVI ACCUM UVIS2-C1 F606W 1 none 1 none 1 N/A S K1C-SUB 288P 1 WFC3/UVI ACCUM UVIS2-C1 F606W 1 none 2 none 1 N/A S K1C-SUB 288P 1 WFC3/UVI ACCUM UVIS2-C1 F606W 2 none 1 none 1 N/A S K1C-SUB 288P 1 WFC3/UVI ACCUM UVIS2-C1 F606W 2 none 2 none 1 N/A S K1C-SUB 288P 1 WFC3/UVI ACCUM UVIS2-C1 F606W 3 none 1 none 1 N/A S K1C-SUB 288P 1 WFC3/UVI ACCUM UVIS2-C1 F606W 3 none 2 none 1 N/A S K1C-SUB 288P 1 WFC3/UVI ACCUM UVIS2-C1 F606W 4 none 1 none 1 N/A S K1C-SUB 288P 1 WFC3/UVI ACCUM UVIS2-C1 F606W 4 none 2 none 1 N/A S K1C-SUB 15481( 4) - 15-Apr-2019 13:25:31 - [ 6] Visit: 02 Visit Requirements: BETWEEN 20-DEC-2018:00:00:00 AND 03-JAN-2019:00:00:00 On Hold Comments: Additional Comments: The flash warning disappears when using the zodiacal light model for the actual position of the target close to the ecliptic. 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 288P WFC3/UVI ACCUM UVIS2-C1K F606W CR-SPLIT=NO 2 230 S PATTERN 1 1 S 1C-SUB (1840 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 | ------------------------------------------------------------------------------------------------------------------------------------ 288P 1 WFC3/UVI ACCUM UVIS2-C1 F606W 1 none 1 none 1 N/A S K1C-SUB 288P 1 WFC3/UVI ACCUM UVIS2-C1 F606W 1 none 2 none 1 N/A S K1C-SUB 288P 1 WFC3/UVI ACCUM UVIS2-C1 F606W 2 none 1 none 1 N/A S K1C-SUB 288P 1 WFC3/UVI ACCUM UVIS2-C1 F606W 2 none 2 none 1 N/A S K1C-SUB 288P 1 WFC3/UVI ACCUM UVIS2-C1 F606W 3 none 1 none 1 N/A S K1C-SUB 288P 1 WFC3/UVI ACCUM UVIS2-C1 F606W 3 none 2 none 1 N/A S K1C-SUB 288P 1 WFC3/UVI ACCUM UVIS2-C1 F606W 4 none 1 none 1 N/A S K1C-SUB 288P 1 WFC3/UVI ACCUM UVIS2-C1 F606W 4 none 2 none 1 N/A S K1C-SUB 15481( 4) - 15-Apr-2019 13:25:31 - [ 7] Visit: 03 Visit Requirements: BETWEEN 15-JAN-2019:00:00:00 AND 30-JAN-2019:00:00:00 On Hold Comments: Additional Comments: The flash warning disappears when using the zodiacal light model for the actual position of the target close to the ecliptic. 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 288P WFC3/UVI ACCUM UVIS2-C1K F606W CR-SPLIT=NO 2 230 S PATTERN 1 1 S 1C-SUB (1840 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 | ------------------------------------------------------------------------------------------------------------------------------------ 288P 1 WFC3/UVI ACCUM UVIS2-C1 F606W 1 none 1 none 1 N/A S K1C-SUB 288P 1 WFC3/UVI ACCUM UVIS2-C1 F606W 1 none 2 none 1 N/A S K1C-SUB 288P 1 WFC3/UVI ACCUM UVIS2-C1 F606W 2 none 1 none 1 N/A S K1C-SUB 288P 1 WFC3/UVI ACCUM UVIS2-C1 F606W 2 none 2 none 1 N/A S K1C-SUB 288P 1 WFC3/UVI ACCUM UVIS2-C1 F606W 3 none 1 none 1 N/A S K1C-SUB 288P 1 WFC3/UVI ACCUM UVIS2-C1 F606W 3 none 2 none 1 N/A S K1C-SUB 288P 1 WFC3/UVI ACCUM UVIS2-C1 F606W 4 none 1 none 1 N/A S K1C-SUB 288P 1 WFC3/UVI ACCUM UVIS2-C1 F606W 4 none 2 none 1 N/A S K1C-SUB 15481( 4) - 15-Apr-2019 13:25:31 - [ 8] Visit: 04 Visit Requirements: BETWEEN 16-FEB-2019:00:00:00 AND 06-MAR-2019:00:00:00 On Hold Comments: Additional Comments: The flash warning disappears when using the zodiacal light model for the actual position of the target close to the ecliptic. 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 288P WFC3/UVI ACCUM UVIS2-C1K F606W CR-SPLIT=NO 2 230 S PATTERN 1 1 S 1C-SUB (1840 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 | ------------------------------------------------------------------------------------------------------------------------------------ 288P 1 WFC3/UVI ACCUM UVIS2-C1 F606W 1 none 1 none 1 N/A S K1C-SUB 288P 1 WFC3/UVI ACCUM UVIS2-C1 F606W 1 none 2 none 1 N/A S K1C-SUB 288P 1 WFC3/UVI ACCUM UVIS2-C1 F606W 2 none 1 none 1 N/A S K1C-SUB 288P 1 WFC3/UVI ACCUM UVIS2-C1 F606W 2 none 2 none 1 N/A S K1C-SUB 288P 1 WFC3/UVI ACCUM UVIS2-C1 F606W 3 none 1 none 1 N/A S K1C-SUB 288P 1 WFC3/UVI ACCUM UVIS2-C1 F606W 3 none 2 none 1 N/A S K1C-SUB 288P 1 WFC3/UVI ACCUM UVIS2-C1 F606W 4 none 1 none 1 N/A S K1C-SUB 288P 1 WFC3/UVI ACCUM UVIS2-C1 F606W 4 none 2 none 1 N/A S K1C-SUB 15481( 4) - 15-Apr-2019 13:25:31 - [ 9] Visit: 05 Visit Requirements: BETWEEN 06-MAY-2019:00:00:00 AND 27-MAY-2019:00:00:00 On Hold Comments: Additional Comments: The flash warning disappears when using the zodiacal light model for the actual position of the target close to the ecliptic. 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 288P WFC3/UVI ACCUM UVIS2-C1K F606W CR-SPLIT=NO 2 230 S PATTERN 1 1 S 1C-SUB (1840 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 | ------------------------------------------------------------------------------------------------------------------------------------ 288P 1 WFC3/UVI ACCUM UVIS2-C1 F606W 1 none 1 none 1 N/A S K1C-SUB 288P 1 WFC3/UVI ACCUM UVIS2-C1 F606W 1 none 2 none 1 N/A S K1C-SUB 288P 1 WFC3/UVI ACCUM UVIS2-C1 F606W 2 none 1 none 1 N/A S K1C-SUB 288P 1 WFC3/UVI ACCUM UVIS2-C1 F606W 2 none 2 none 1 N/A S K1C-SUB 288P 1 WFC3/UVI ACCUM UVIS2-C1 F606W 3 none 1 none 1 N/A S K1C-SUB 288P 1 WFC3/UVI ACCUM UVIS2-C1 F606W 3 none 2 none 1 N/A S K1C-SUB 288P 1 WFC3/UVI ACCUM UVIS2-C1 F606W 4 none 1 none 1 N/A S K1C-SUB 288P 1 WFC3/UVI ACCUM UVIS2-C1 F606W 4 none 2 none 1 N/A S K1C-SUB 15481( 4) - 15-Apr-2019 13:25:31 - [ 10] Summary Form for Proposal 15481 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures UVIS2-C1K1C-SUB ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFC3/UVIS ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters CR-SPLIT=NO ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements BETWEEN 01-NOV-2018:00:00:00 AND 15-NOV-2018:00:00:00, BETWEEN 06-MAY-2019:00:00:00 AND 27-MAY-2019:00:00:00, BETWEEN 15-JAN-2019:00:00:00 AND 30-JAN-2019:00:00:00, BETWEEN 16-FEB-2019:00:00:00 AND 06-MAR-2019:00:00:00, BETWEEN 20-DEC-2018:00:00:00 AND 03-JAN-2019:00:00:00, PATTERN 1 1 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F606W ------------------------------------------------------------------------------------------------------------------------------------ Target Names 288P ------------------------------------------------------------------------------------------------------------------------------------