0 Assigned ID: 1210 ----- Attempting Submission 1 (Fri Jan 17 14:32:34 GMT 2020) ----- HST Phase I Proposal 1210 (hst27_mc_288P_apt) successfully submitted. Receipt: # 1210-1 ----- Attempting Submission 2 (Fri Jan 17 20:06:46 GMT 2020) ----- 0 ----- Attempting Submission 1 (Mon Mar 09 13:37:09 GMT 2020) ----- We request 6 orbits of HST/WFC3 in May 2020 measure the rotation periods, elongation and cross-sections of the components of binary main-belt comet 288P. This will allow us to provide constraints on the formation and evolution of this unusual binary system and for the first time to constrain the bulk density of a main-belt comet. The 288P system is special both because of its unusual orbital properties (wide semi-major axis combined with near-equal component size) and because it is the only confirmed solar system binary showing sublimation-driven activity. At present, it is not clear if such systems are indeed rare, or merely affected by a strong detection bias against them. To better judge this, it is mandatory to understand the formation and past evolution of the system, and a potential interrelation between the activity and the binary formation. To constrain binary formation and evolution models, an accurate knowledge of the masses, shapes and angular momenta of the components is required, which we seek to obtain by the proposed observations. These will allow us measure the individual brightness of the components for a significant fraction of the 16h rotation period reported for the more elongated component. HST is the only telescope able to spatially separate the two components (max. separation about 0.08 arcsec). We did not propose these observations at the time of the regular Cycle 27 deadline because then we had not yet found an orbit solution that would have enabled us to predict the times of maximum component separation with sufficient reliability. 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 about 0.08arcsec in 2020 May and have a combined brightness of about V=22mag. The target will be brightest (21.8mag) on May 04, maximising S/N. Hence an observation as close as possible in time to this date is desirable. 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 a small multiple of 16h (~48h) will also be acceptable. Hence the priorities for scheduling should be as follows: 1. All orbits should be scheduled within about 48h. 2. Scheduling should be as close in time as possible to May 04, but not before Apr-25 and not after May 31 to ensure maximum spatial component separation. 3. If two possible dates exist that have similar distance in time to May 04, the later one is preferable, because the spatial separation will be larger at comparable brightness. Each visit consists of 8 exposures of 280s, using a 2-point linear dither pattern to mitigate bad pixels and the C515C 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. The dither pattern and sub-frame are different from those outlined in the proposal, because we trade some comparability to existing date for increased S/N, which is most crucial to reach our science objectives. 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 >100deg, hence the enlarged solar exclusion zone will not pose a problem. 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 and fit the rotational lightcurves. Yoonyoung Kim is an expert in the dynamical modeling of dust moving under the action of gravity, solar radiation pressure and initial velocity distribution. 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 Astronomy 3 false false false false false false false SUPPORTED SOLAR SYSTEM ASTEROID Binary asteroid TYPE=ASTEROID,A=3.047167629727458,E=0.2011952883437459,I=3.240682641168021 ,O=83.19068811025544,W=281.2529259614446,M=188.6246594824991,EQUINOX=J2000,EPOCH=29-APR-2014:00:00:00,EpochTimeScale=TDB EARTH WFC3/UVIS Imaging No No F606W WFC3/UVIS Imaging No No F606W WFC3/UVIS Imaging No No F606W POS-TARG DITHER 0.145 LINE false false 2 46.84 WFC3-UVIS-DITHER-LINE 1 false 1583759578382 /home/agarwal/Proposals/HST27_MC_288P/OP-cache/phase2_200309_ja-v01.xml Using ephemeris for target 16073-01-288P ephemeris data for target 16073-01-288P does not cover planning interval. Physical constraints are assumed to be unschedulable outside of the ephemeris data. Planning interval: 19.213 to 21.089. ephemeris interval: 20.060 to 22.060 Timing link suitability includes constraints ([Group (01 02 03) Within 2.0 days]) The scheduling data was generated by CASM 28.0. CASM was run in Phase II mode. The target will be brightest on May 04, hence scheduling as close to this date as possible would maximise S/N and science return. (Tic-Visit :proposal-id 16073 :visit-id "01" :proposal-version -1 :trans-version "20191203" :date "09-Mar-2020 14:12:57.0" :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 16073 :visit-id "01" :obset-id "01" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 16073 :visit-id "01" :orbit-number 1 :pcs-time 393 :si-vis-utilization 2696 :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 3142 :pcs-gap 0 ) (Tic-Orbit :proposal-id 16073 :visit-id "01" :orbit-number 2 :pcs-time 302 :si-vis-utilization 2664 :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 3142 :pcs-gap 0 ) true 2 0 1583760012522 /home/agarwal/Proposals/HST27_MC_288P/OP-cache/phase2_200309_ja-v02.xml Using ephemeris for target 16073-02-288P ephemeris data for target 16073-02-288P does not cover planning interval. Physical constraints are assumed to be unschedulable outside of the ephemeris data. Planning interval: 19.213 to 21.089. ephemeris interval: 20.060 to 22.060 Timing link suitability includes constraints ([Group (01 02 03) Within 2.0 days]) The scheduling data was generated by CASM 28.0. CASM was run in Phase II mode. (Tic-Visit :proposal-id 16073 :visit-id "02" :proposal-version -1 :trans-version "20191203" :date "09-Mar-2020 14:20:12.0" :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 16073 :visit-id "02" :obset-id "02" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 16073 :visit-id "02" :orbit-number 1 :pcs-time 393 :si-vis-utilization 2696 :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 3142 :pcs-gap 0 ) (Tic-Orbit :proposal-id 16073 :visit-id "02" :orbit-number 2 :pcs-time 302 :si-vis-utilization 2664 :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 3142 :pcs-gap 0 ) true 2 0 1583759969211 /home/agarwal/Proposals/HST27_MC_288P/OP-cache/phase2_200309_ja-v03.xml Using ephemeris for target 16073-03-288P ephemeris data for target 16073-03-288P does not cover planning interval. Physical constraints are assumed to be unschedulable outside of the ephemeris data. Planning interval: 19.213 to 21.089. ephemeris interval: 20.060 to 22.060 Timing link suitability includes constraints ([Group (01 02 03) Within 2.0 days]) The scheduling data was generated by CASM 28.0. CASM was run in Phase II mode. 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