14884( 3) - 29-Nov-2016 13:27:25 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 14884 Version: 3 Check-in Time: 29-Nov-2016 13:27:25 STScI Edit Number: 0 Title Characterising the dust ejection process in the first known active binary asteroid system 288P/300163. ------------------------------------------------------------------------------------ Type Cycle GO 24 ------------------------------------------------------------------------------------ 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 four orbits of MC time to monitor the dust ejected from the recently discovered, first known active binary asteroid system 288P/300163, using WFC3. The key aim is to trace the influence of the binary nature and/or potential rapid rotation on the sublimation-driven activity, in order to understand if the activity was triggered by the same process that led to the formation of the binary, or if the two processes were independent. Both dust release and binary formation can be a consequence of rapid rotation, and 288P is the first object showing both these phenomena, which may emphasise the importance of the YORP-effect in re-shaping the asteroid belt. The proposed observations will exploit the change in projection related to the Earth's crossing the orbital plane of 288P in 2016 December to reconstruct the three-dimensional distribution of the dust ejected from the 288P system. As this coincides with the expected maximum of activity (perihelion is on November 08) and a close approach to Earth (perigee was on September-10 at 1.45 AU), we will follow the dust ejection process at supreme temporal and spatial resolution. The activity of 288P is expected to cease around 2017 February, which triggers our request for mid-cycle time. ------------------------------------------------------------------------------------ Observations Description ------------------------ The purpose of the program is to observe active asteroid 288P during December 2016 through February 2017. One orbit should be scheduled as close a possible to December 14 in order to measure the vertical extent of the dust trail while the Earth crosses the orbital plane of 288P. The remaining 3 orbits should be spaced at 2-3 week intervals and before 288P enters the solar exclusion zone in mid-February. This will give us three high-resolution measurements of the dust sheet from a perspective south of the orbital plane, complementary to our existing observations (from GO 14790 and GO 14864) obtained from a northern perspective. The three measurements will allow us to sufficiently sample the temporal evolution of the dust tail and coma to distinguish between episodic and continuous emission. We will follow the same successful observation strategy as for our programs GO 14790 and 14864, ensuring a maximum comparability of the data. 14884( 3) - 29-Nov-2016 13:27:25 - [ 2] The orbital visibility for a solar system target near the ecliptic plane is 54 min (Section 6.3 of the HST Primer document). In each orbit, we will take 8 exposures of $\sim$230\, s using the 1k subarray of WFC3. We will perform a subsampling dither box pattern, obtaining 2 exposures at each dither point. We will carefully drizzle our subsampled images to a finer output pixel scale to extract the extra spatial information gathered by our subsampling strategy. This enhanced resolution will allow us to extract the maximum possible information on the two nuclei and the dust distribution in the innermost coma. The dithering will also enable us to reject hot pixels and cosmic ray hits. This strategy gives us a total exposure time of 1840\, s = 30min per orbit, and estimated overheads of 6\, min for guide-star acquisition, 2.6\, min for the first exposure, a total of 14.7\, min for the subsequent 7 exposures, and 1.5\, min for the three spacecraft maneuvers required for dithering, which adds up to a total execution time of 54\, min per orbit. Our observations of GO 14790 and 14864 show that this exposure time is adequate to detect the dust tail at good S/N. We will use the wide bandpass filter F606W for an optimum trade-off between sensitivity and highest resolution: the bandpass (475 -- 700 nm) covers the maximum of the solar spectrum, and is in the wavelength range where the PSF is smallest (FWHM$<$0.07 arcsec, from the WFC3 instrument handbook for Cycle 24), 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 and 14864, enabling a direct comparison of the data sets. ------------------------------------------------------------------------------------ 14884( 3) - 29-Nov-2016 13:27:25 - [ 3] TARGET LIST Solar System Targets ------------------------------------------------------------------------------------------------------------------------------------ TARGET NUMBER: 1 TARGET NAME: 288P ------------------------------------------------------------------------------------------------------------------------------------ TARGET DESCRIPTION: COMET active asteroid ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 1 TARGET POSITION LEVEL 2 TYPE=COMET, Q=2.437997636061935, E=.2002773126787514, I=3.239254302184838, O=83.22502588733704, W=281.9669249151093, T=18-JUL-2011:22:51:20, TTimeScale=UTC, EQUINOX=J2000, EPOCH=19-JUN-2010:00:00:00, EpochTimeScale=TDB ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 3 WINDOWS ------------------------------------------------------------------------------------------------------------------------------------ DATA COMMENTS V = 20 +/- 1 Ephemeris Center: EARTH Extended: YES ------------------------------------------------------------------------------------------------------------------------------------ 14884( 3) - 29-Nov-2016 13:27:25 - [ 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 ------------------------------------------------------------------------------------------------------------------------------------ 14884( 3) - 29-Nov-2016 13:27:25 - [ 5] Visit: 01 Visit Requirements: BETWEEN 14-DEC-2016:00:00:00 AND 16-DEC-2016:00:00:00 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 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 14884( 3) - 29-Nov-2016 13:27:25 - [ 6] Visit: 02 Visit Requirements: BETWEEN 26-DEC-2016:00:00:00 AND 01-JAN-2017:00:00:00 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 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 14884( 3) - 29-Nov-2016 13:27:25 - [ 7] Visit: 03 Visit Requirements: BETWEEN 13-JAN-2017:00:00:00 AND 20-JAN-2017:00:00:00 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 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 14884( 3) - 29-Nov-2016 13:27:25 - [ 8] Visit: 04 Visit Requirements: BETWEEN 30-JAN-2017:00:00:00 AND 05-FEB-2017:00:00:00 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 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 14884( 3) - 29-Nov-2016 13:27:25 - [ 9] Summary Form for Proposal 14884 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures UVIS2-C1K1C-SUB ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFC3/UVIS ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters CR-SPLIT=NO ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements BETWEEN 13-JAN-2017:00:00:00 AND 20-JAN-2017:00:00:00, BETWEEN 14-DEC-2016:00:00:00 AND 16-DEC-2016:00:00:00, BETWEEN 26-DEC-2016:00:00:00 AND 01-JAN-2017:00:00:00, BETWEEN 30-JAN-2017:00:00:00 AND 05-FEB-2017:00:00:00, PATTERN 1 1 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F606W ------------------------------------------------------------------------------------------------------------------------------------ Target Names 288P ------------------------------------------------------------------------------------------------------------------------------------