0Is main-belt comet 288P a triple system?We request 6 mid-cycle orbits using WFC3 in 2021 June to probe the newly suspected triple nature of main-belt comet 288P. This object is unique. It has wide separation, nearly equal-sized components, and also displays repetitive comet-like activity. 288P is one of only a few known asteroid binaries whose components can be spatially resolved by WFC3. Archival WFC3 observations obtained two months after the Cycle 28 deadline reveal that 288P is likely triple. That is, the light curve of one of the two main components is best represented as the sum of the lightcurves of two (spatially unresolved) components with different periods. Additional data are needed to confirm the third component. Successful identification of the third component would make 288P the first-ever detected triple asteroid system to exhibit comet-like activity, and provide crucial constraints on asteroid break-up models and on the role of activity-causing ice sublimation. We emphasize that these measurements maximally exploit the capabilities of HST for high resolution imaging. HST is the only telescope able to spatially separate the two main nuclei (maximum separation about 0.1 arcsec) and hence to measure their rotational lightcurves separately. The proposed observations are time-critical to be carried out in 2021 June, which is the last opportunity to spatially separate the two main components before the return of dust activity in fall 2021.The goal of this program is to measure the time-variability of the brightness of the two components of binary asteroid 288P. We expect that the components will be separated by <0.1arcsec in 2021 September and have a combined brightness of about V=22mag.
All 6 visits should be scheduled as close in time as possible, ideally as 3 pairs of orbits separated each by only one orbit for gyro reset. But distributing the orbits across a time interval of ~24h will also be acceptable (which can be relaxed as needed for scheduling). Hence the timing requirements are as follows:
Visit 1: BETWEEN Sep 27 and Oct 01, GROUP Visits 01, 02, 03 WITHIN 24H
Each visit consists of 8 exposures of ~240s, using a 2-point linear dither pattern to mitigate bad pixels and the C512C sub-frame to minimise read-out time. If the actual orbital visibility is shorter than expected in APT, then the exposure time can be shortened such that all 8 exposures fit into one orbit.
Should the program have to be carried out in 1gyro mode we can shorten the exposure time to adapt to the increased time for guide star acquisition. The target will be at solar elongations >110deg, hence the enlarged solar exclusion zone will not pose a problem.Yoonyoung Kim is an expert in the dynamical modeling of dust moving under the action of gravity, solar radiation pressure and initial velocity distribution, and carried out the lightcurve analysis on GO 16073 data, and will apply the same methods to the data proposed to obtain here.
Jessica Agarwal previously analyzed HST data on active asteroids to place constraints on the dust ejection process from the dust dynamics and photometry. She is the PI of several HST programs that lead to the discovery and further analysis of the unusual binary main-belt comet 288P. She will carry out the PSF fitting to measure the component separations and brightnesses.
David Jewitt has an extensive record of research into the study of small solar system bodies, especially the Kuiper belt objects and the cometary nuclei. In the last decade he has written >20 refereed papers based on Hubble data. He will contribute to the measurement, analysis and interpretation of the data and to writing up the results for publication.
Max Mutchler is an expert on Hubble's cameras. He will contribute to the subsampling observing strategy, and special image processing for moving targets.
Harold Weaver is a veteran Hubble observer, mostly of comets, with many Hubble-related publications. He will contribute to optimizing the observation strategy and to interpreting the data.
Stephen Larson is an experienced investigator of small Solar system bodies and the PI of the Catalina Sky Survey, from which previous HST targets including the outburst of (596) Scheila, P/2013 R3 and 313P were discovered. He will contribute to the data interpretation.Solar System Astronomy3falsefalsefalsefalsefalsefalsefalsefalseSUPPORTEDSOLAR SYSTEMNOASTEROIDbinary asteroidTYPE=ASTEROID,A=3.049316706845886,E=0.2011145348983784,I=3.240027217147757
,O=83.18987601023933,W=281.0531996557008,M=359.7694035685469,EQUINOX=J2000,EPOCH=07-NOV-2016:00:00:00,EpochTimeScale=TDBEARTHWFC3/UVISImagingNoNoF606WWFC3/UVISImagingNoNoF606WWFC3/UVISImagingNoNoF606WPOS-TARGDITHER0.145LINEfalsefalse246.84WFC3-UVIS-DITHER-LINE1falseUsing ephemeris for target 16501-01-288P-UPDATE3ephemeris data for target 16501-01-288P-UPDATE3 does not cover planning interval. Physical constraints are assumed to be unschedulable outside of the ephemeris data. Planning interval: 20.214 to 22.244. ephemeris interval: 21.243 to 23.244Timing link suitability includes constraints ([Group (01 02 03) Within 1.0 days])The scheduling data was generated by CASM 29.2.CASM was run in Phase II mode.(Tic-Visit
:proposal-id 16501
:visit-id "01"
:proposal-version -1
:trans-version "20210514"
:date "02-Sep-2021 13:44:47.0"
:trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0
:FATAL-ERRORS 0 :CONTINUABLE-FATALS 0)
:number-of-orbits 2
:saa-model "29"
:si-bright-earth-limb-angle 20.0
:data-volume 73232
:tdrss-contact-duration 0
:coron NIL
)
(Tic-Obset
:proposal-id 16501
:visit-id "01"
:obset-id "01"
:pcs-mode "FGS"
)
(Tic-Orbit
:proposal-id 16501
:visit-id "01"
:orbit-number 1
:pcs-time 393
:si-vis-utilization 2372
:al-overhead-at-end 0
:internal-dur-at-end 0
:dark-offset NIL
:dark-utilization 0
:max-dark-utilization 1920
:low-sky "N"
:pcs-visibility 2782
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(Tic-Orbit
:proposal-id 16501
:visit-id "01"
:orbit-number 2
:pcs-time 392
:si-vis-utilization 2340
:al-overhead-at-end 0
:internal-dur-at-end 117
:dark-offset NIL
:dark-utilization 0
:max-dark-utilization 1920
:low-sky "N"
:pcs-visibility 2782
:pcs-gap 0
)false20Using ephemeris for target 16501-02-288P-UPDATE3ephemeris data for target 16501-02-288P-UPDATE3 does not cover planning interval. Physical constraints are assumed to be unschedulable outside of the ephemeris data. Planning interval: 20.214 to 22.244. ephemeris interval: 21.243 to 23.244Timing link suitability includes constraints ([Group (01 02 03) Within 1.0 days])The scheduling data was generated by CASM 29.2.CASM was run in Phase II mode.(Tic-Visit
:proposal-id 16501
:visit-id "02"
:proposal-version -1
:trans-version "20210514"
:date "02-Sep-2021 13:49:14.0"
:trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0
:FATAL-ERRORS 0 :CONTINUABLE-FATALS 0)
:number-of-orbits 2
:saa-model "29"
:si-bright-earth-limb-angle 20.0
:data-volume 73232
:tdrss-contact-duration 0
:coron NIL
)
(Tic-Obset
:proposal-id 16501
:visit-id "02"
:obset-id "02"
:pcs-mode "FGS"
)
(Tic-Orbit
:proposal-id 16501
:visit-id "02"
:orbit-number 1
:pcs-time 393
:si-vis-utilization 2372
:al-overhead-at-end 0
:internal-dur-at-end 0
:dark-offset NIL
:dark-utilization 0
:max-dark-utilization 1920
:low-sky "N"
:pcs-visibility 2782
:pcs-gap 0
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(Tic-Orbit
:proposal-id 16501
:visit-id "02"
:orbit-number 2
:pcs-time 392
:si-vis-utilization 2340
:al-overhead-at-end 0
:internal-dur-at-end 117
:dark-offset NIL
:dark-utilization 0
:max-dark-utilization 1920
:low-sky "N"
:pcs-visibility 2782
:pcs-gap 0
)false20Using ephemeris for target 16501-03-288P-UPDATE3ephemeris data for target 16501-03-288P-UPDATE3 does not cover planning interval. Physical constraints are assumed to be unschedulable outside of the ephemeris data. Planning interval: 20.214 to 22.244. ephemeris interval: 21.243 to 23.244Timing link suitability includes constraints ([Group (01 02 03) Within 1.0 days])The scheduling data was generated by CASM 29.2.CASM was run in Phase II mode.(Tic-Visit
:proposal-id 16501
:visit-id "03"
:proposal-version -1
:trans-version "20210514"
:date "02-Sep-2021 13:58:05.0"
:trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0
:FATAL-ERRORS 0 :CONTINUABLE-FATALS 0)
:number-of-orbits 2
:saa-model "29"
:si-bright-earth-limb-angle 20.0
:data-volume 73232
:tdrss-contact-duration 0
:coron NIL
)
(Tic-Obset
:proposal-id 16501
:visit-id "03"
:obset-id "03"
:pcs-mode "FGS"
)
(Tic-Orbit
:proposal-id 16501
:visit-id "03"
:orbit-number 1
:pcs-time 393
:si-vis-utilization 2372
:al-overhead-at-end 0
:internal-dur-at-end 0
:dark-offset NIL
:dark-utilization 0
:max-dark-utilization 1920
:low-sky "N"
:pcs-visibility 2782
:pcs-gap 0
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(Tic-Orbit
:proposal-id 16501
:visit-id "03"
:orbit-number 2
:pcs-time 392
:si-vis-utilization 2340
:al-overhead-at-end 0
:internal-dur-at-end 117
:dark-offset NIL
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:max-dark-utilization 1920
:low-sky "N"
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:pcs-gap 0
)false20