16463( 9) - 06-Jul-2021 14:03:52 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 16463 Version: 9 Check-in Time: 06-Jul-2021 14:03:52 STScI Edit Number: 5 Title Active Asteroid P/2020 O1 ------------------------------------------------------------------------------------ Type Cycle GO 28 ------------------------------------------------------------------------------------ Investigators Contact? PI: Dr. David Jewitt University of California - Los Angeles Y CoI: Dr. Jessica Agarwal Technische Universitaet Braunschweig N CoI: Dr. Yoonyoung Kim Technische Universitaet Braunschweig N CoI: Max Mutchler Space Telescope Science Institute Y CoI: Dr. Harold A. Weaver The Johns Hopkins University Applied Y Physics Laboratory CoI: Dr. Jing Li University of California - Los Angeles N ------------------------------------------------------------------------------------ Abstract Exploratory observations of newly discovered active asteroid P/2020 O1 show evidence for protracted mass-loss and very low velocity ejection, consistent with prolonged sublimation of ice as the driving mechanism. We request mid-Cycle time in order to refine the analysis of P/2020 O1 using data from a variety of observational geometries, coupled with a sophisticated Monte Carlo dust dynamics model. Observations at high resolution and at a range of times and geometries are needed to definitively determine the mass loss mechanism. If water ice sublimation is confirmed, P/2020 O1 would be the icy asteroid with the smallest semimajor axis (highest temperature), setting new bounds on the distribution of ice in the asteroid belt. ------------------------------------------------------------------------------------ Observations Description ------------------------ Our basic observing strategy is to take multiple long exposures (348 s) using WFC3 and a wide bandpass filter F350LP for maximum sensitivity. The F350LP filter provides a 1.6x higher count rate for a target with a solar-type spectrum, so we plan to use it. We also plan to dither the exposures to mitigate the effects from bad pixels, cosmic rays, and the inter-chip gap. The apparent rates of motion are easily within Hubbles tracking capabilities. These rates are also slow enough to keep a single pair of guide stars within the FGS pickles for an entire visibility window. The current 1-sigma ephemeris uncertainty of P/2020 O1 is about 4 arcsec and grows with time. However, we will improve the ephemeris iteratively, with each successive visit refining the orbit to get ready for the next. As a result, ephemeris errors will be negligible compared to the WFC3 field-of-view of 162 x 162 arcsec, so that ephemeris issues are of no concern to this observation. We understand that we may have essentially no control over the spacecraft roll angle, which means we will not be able to optimize the orientation of the dust tail on the CCD (i.e., to orient the tail along the longest dimension of the detector). However, the field-of-view of the camera is large enough that we should obtain excellent data on a portion of the tail, no matter what spacecraft roll angle is used. We request 5 orbits to characterize the progression of activity in P/2020 O1. The 16463( 9) - 06-Jul-2021 14:03:52 - [ 2] temporal distribution of the orbits is determined in part by the movement of the target into the 54 degree 4 Sun-exclusion zone of HST and in part by the changing heliocentric distance of the object. Visit 1 is one orbit as early as possible in late November/early December, to bridge the gap from the last observations in September. Visit 2 is one orbit late in 2020 December, close to the entry of P/2020 O1 into the Sun-exclusion zone on UT December 25. The heliocentric distance will be about 2.50 AU and the angle of the Earth above the orbital plane is near the maximum 1.9 degrees, providing the best perspective on the spatial distribution of dust and strong leverage for the dust dynamics models. Visit 3 is one orbit in 2021 July, as close as possible to the emergence of P/2020 O1 from the Sun-exclusion zone on UT 2021 July 6. The heliocentric distance is 2.75 AU and the angle from the orbit plane -1.6 degrees, again providing strong constraint on the dust models. Visit 4 is one orbit in 2021 August, about one month following Visit 3. Visit 5 is one orbit in 2021 September, about one month following Visit 4. With heliocentric distance 2.80 AU, we will sample the target similar to its 2.96 AU aphelion from an out-of-plane angle 0 degrees. Depending on the status of the activity, this is likely to provide our best constraint on the bare nucleus. Visits 1 and 2, together with existing ToO observations from September, will provide coverage of the dust development over 4 months following the 2020 May perihelion. If P/2020 O1 continues to be active in 2021, then Visits 3, 4 and 5 will extend the sampling of the activity for a full year. If activity should shut down before the summer, these visits will sample the evolution of the largest particles already ejected, expected to linger near the nucleus. These observations will provide powerful constraints on large particle ejection from P/2020 O1. Previously, large particles in comets have been studied mainly using thermal wavelengths, offering angular resolution 100 times poorer than HST. The dates of each visit are not critical at the level of a week to 10 days. The proposed scheduling will bridge the gap to observations to be proposed for Cycle 29. ------------------------------------------------------------------------------------ 16463( 9) - 06-Jul-2021 14:03:52 - [ 3] TARGET LIST Solar System Targets ------------------------------------------------------------------------------------------------------------------------------------ TARGET NUMBER: 1 TARGET NAME: P2020-O1 ------------------------------------------------------------------------------------------------------------------------------------ TARGET DESCRIPTION: ASTEROID active asteroid ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 1 TARGET POSITION LEVEL 2 TYPE=COMET, Q=2.329339261954623, E=0.1198591438297583, I=5.22346273219021 , O=175.9889902558661, W=104.8273219832331, T=03-MAY-2020:18:25:03, TTimeScale=TDB, EQUINOX=J2000, EPOCH=28-JUL-2020:00:00:00, EpochTimeScale=TDB ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 3 WINDOWS ------------------------------------------------------------------------------------------------------------------------------------ DATA COMMENTS V = 22 +/- 3 Ephemeris Center: EARTH Extended: YES ------------------------------------------------------------------------------------------------------------------------------------ TARGET NUMBER: 2 TARGET NAME: P2020-O1-V3 ------------------------------------------------------------------------------------------------------------------------------------ TARGET DESCRIPTION: ASTEROID active asteroid ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 1 TARGET POSITION LEVEL 2 TYPE=COMET, Q=2.329334434263673, E=0.1198571503419016, I=5.223476693804598 , O=175.9886843766403, W=104.827482351413, T=03-MAY-2020:18:24:37, TTimeScale=TDB, EQUINOX=J2000, EPOCH=29-JUL-2020:00:00:00, EpochTimeScale=TDB ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 3 WINDOWS ------------------------------------------------------------------------------------------------------------------------------------ DATA COMMENTS V = 22 +/- 3 Ephemeris Center: EARTH Extended: YES ------------------------------------------------------------------------------------------------------------------------------------ 16463( 9) - 06-Jul-2021 14:03:52 - [ 4] 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 ------------------------------------------------------------------------------------------------------------------------------------ 16463( 9) - 06-Jul-2021 14:03:52 - [ 5] Visit: 01 Visit Requirements: BETWEEN 23-NOV-2020:06:00:00 AND 26-NOV-2020:12:00:00; BETWEEN 27-NOV-2020:00:00:00 AND 02-DEC-2020:00:00:00 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 P2020-O1 WFC3/UVI ACCUM UVIS2-2K2 F350LP 3 260 S SEQ 1 NON-INT; PATTERN 1 S C-SUB (1560 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 | ------------------------------------------------------------------------------------------------------------------------------------ P2020-O1 1 WFC3/UVI ACCUM UVIS2-2K F350LP 1 none 1 none 1 N/A S 2C-SUB P2020-O1 1 WFC3/UVI ACCUM UVIS2-2K F350LP 1 none 2 none 1 N/A S 2C-SUB P2020-O1 1 WFC3/UVI ACCUM UVIS2-2K F350LP 1 none 3 none 1 N/A S 2C-SUB P2020-O1 1 WFC3/UVI ACCUM UVIS2-2K F350LP 2 none 1 none 1 N/A S 2C-SUB P2020-O1 1 WFC3/UVI ACCUM UVIS2-2K F350LP 2 none 2 none 1 N/A S 2C-SUB P2020-O1 1 WFC3/UVI ACCUM UVIS2-2K F350LP 2 none 3 none 1 N/A S 2C-SUB 16463( 9) - 06-Jul-2021 14:03:52 - [ 6] Visit: 02 Visit Requirements: BETWEEN 21-DEC-2020:00:00:00 AND 28-DEC-2020:00:00:00 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 P2020-O1 WFC3/UVI ACCUM UVIS2-2K2 F350LP 3 260 S SEQ 1 NON-INT; PATTERN 1 S C-SUB (1560 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 | ------------------------------------------------------------------------------------------------------------------------------------ P2020-O1 1 WFC3/UVI ACCUM UVIS2-2K F350LP 1 none 1 none 1 N/A S 2C-SUB P2020-O1 1 WFC3/UVI ACCUM UVIS2-2K F350LP 1 none 2 none 1 N/A S 2C-SUB P2020-O1 1 WFC3/UVI ACCUM UVIS2-2K F350LP 1 none 3 none 1 N/A S 2C-SUB P2020-O1 1 WFC3/UVI ACCUM UVIS2-2K F350LP 2 none 1 none 1 N/A S 2C-SUB P2020-O1 1 WFC3/UVI ACCUM UVIS2-2K F350LP 2 none 2 none 1 N/A S 2C-SUB P2020-O1 1 WFC3/UVI ACCUM UVIS2-2K F350LP 2 none 3 none 1 N/A S 2C-SUB 16463( 9) - 06-Jul-2021 14:03:52 - [ 7] Visit: 03 Visit Requirements: BETWEEN 07-JUL-2021:06:00:00 AND 23-JUL-2021:03:00:00; BETWEEN 23-JUL-2021:17:30:00 AND 26-JUL-2021:00:00:00 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 P2020-O1-V3 WFC3/UVI ACCUM UVIS2-2K2 F350LP 3 230 S SEQ 1 NON-INT; PATTERN 1 S C-SUB (1380 S) 1 ------------------------------------------------------------------------------------------------------------------------------------ 2 P2020-O1-V3 WFC3/UVI ACCUM UVIS2-2K2 F350LP 3 230 S SEQ 2 NON-INT; PATTERN 1 S C-SUB (1380 S) 2 ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ P2020-O1-V3 1 WFC3/UVI ACCUM UVIS2-2K F350LP 1 none 1 none 1 N/A S 2C-SUB P2020-O1-V3 1 WFC3/UVI ACCUM UVIS2-2K F350LP 1 none 2 none 1 N/A S 2C-SUB P2020-O1-V3 1 WFC3/UVI ACCUM UVIS2-2K F350LP 1 none 3 none 1 N/A S 2C-SUB P2020-O1-V3 1 WFC3/UVI ACCUM UVIS2-2K F350LP 2 none 1 none 1 N/A S 2C-SUB P2020-O1-V3 1 WFC3/UVI ACCUM UVIS2-2K F350LP 2 none 2 none 1 N/A S 2C-SUB P2020-O1-V3 1 WFC3/UVI ACCUM UVIS2-2K F350LP 2 none 3 none 1 N/A S 2C-SUB P2020-O1-V3 2 WFC3/UVI ACCUM UVIS2-2K F350LP 1 none 1 none 2 N/A S 2C-SUB P2020-O1-V3 2 WFC3/UVI ACCUM UVIS2-2K F350LP 1 none 2 none 2 N/A S 2C-SUB P2020-O1-V3 2 WFC3/UVI ACCUM UVIS2-2K F350LP 1 none 3 none 2 N/A S 2C-SUB P2020-O1-V3 2 WFC3/UVI ACCUM UVIS2-2K F350LP 2 none 1 none 2 N/A S 2C-SUB P2020-O1-V3 2 WFC3/UVI ACCUM UVIS2-2K F350LP 2 none 2 none 2 N/A S 2C-SUB P2020-O1-V3 2 WFC3/UVI ACCUM UVIS2-2K F350LP 2 none 3 none 2 N/A S 2C-SUB 16463( 9) - 06-Jul-2021 14:03:52 - [ 8] Visit: 04 Visit Requirements: BETWEEN 19-JUL-2021:00:00:00 AND 23-JUL-2021:03:00:00; BETWEEN 23-JUL-2021:16:00:00 AND 26-JUL-2021:00:00:00; GROUP 04, 03 WITHIN 2.5 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 P2020-O1-V3 WFC3/UVI ACCUM UVIS2-2K2 F350LP 3 230 S SEQ 1 NON-INT; PATTERN 1 S C-SUB (1380 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 | ------------------------------------------------------------------------------------------------------------------------------------ P2020-O1-V3 1 WFC3/UVI ACCUM UVIS2-2K F350LP 1 none 1 none 1 N/A S 2C-SUB P2020-O1-V3 1 WFC3/UVI ACCUM UVIS2-2K F350LP 1 none 2 none 1 N/A S 2C-SUB P2020-O1-V3 1 WFC3/UVI ACCUM UVIS2-2K F350LP 1 none 3 none 1 N/A S 2C-SUB P2020-O1-V3 1 WFC3/UVI ACCUM UVIS2-2K F350LP 2 none 1 none 1 N/A S 2C-SUB P2020-O1-V3 1 WFC3/UVI ACCUM UVIS2-2K F350LP 2 none 2 none 1 N/A S 2C-SUB P2020-O1-V3 1 WFC3/UVI ACCUM UVIS2-2K F350LP 2 none 3 none 1 N/A S 2C-SUB 16463( 9) - 06-Jul-2021 14:03:52 - [ 9] Summary Form for Proposal 16463 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures UVIS2-2K2C-SUB ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFC3/UVIS ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements BETWEEN 07-JUL-2021:06:00:00 AND 23-JUL-2021:03:00:00, BETWEEN 19-JUL-2021:00:00:00 AND 23-JUL-2021:03:00:00, BETWEEN 21-DEC-2020:00:00:00 AND 28-DEC-2020:00:00:00, BETWEEN 23-JUL-2021:16:00:00 AND 26-JUL-2021:00:00:00, BETWEEN 23-JUL-2021:17:30:00 AND 26-JUL-2021:00:00:00, BETWEEN 23-NOV-2020:06:00:00 AND 26-NOV-2020:12:00:00, BETWEEN 27-NOV-2020:00:00:00 AND 02-DEC-2020:00:00:00, GROUP 04, 03 WITHIN 2.5 Orbits, PATTERN 1 1, PATTERN 1 2, SEQ 1 NON-INT, SEQ 2 NON-INT ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F350LP ------------------------------------------------------------------------------------------------------------------------------------ Target Names P2020-O1, P2020-O1-V3 ------------------------------------------------------------------------------------------------------------------------------------