We selected TOO (disruptive), but note that the target falls below 55 degree target-to-sun separation after Thursday, 2023 January 12, which remains outside the 3 week disruptive window through December 22. -334197536 Assigned ID: 3880 ----- Attempting Submission 1 (Tue Dec 20 04:31:51 GMT 2022) ----- HST Phase I Proposal 3880 successfully submitted. Receipt: # 3880-1 Thank you Bill Januszewski and Linda Dressel for your help. NTS: Bill ran the Visit Planner for us. 145857660 ----- Attempting Submission 1 (Fri Dec 23 22:25:36 GMT 2022) ----- Centaurs are minor planets found between the orbits of Jupiter and Neptune. In this region temperatures are too cold for water ice to be sublimate, yet a rare (<20) subset of Centaurs display cometary activity such as a tail or coma. Observations by our team of one such active Centaur, P/2020 MK4, revealed the object had dimmed dramatically, by over 4 magnitudes. A distinct cloud of material has been consistently observable, even in the absence of a clearly discernible nucleus. We present two hypotheses to explain the vanishing of active Centaur P/2020 MK4: (1) the object is disintegrating or dissipating, or (2) the object is much smaller than previously estimated and is now entering a quiescent phase. Notably, the object has a nearly circular orbit (e=0.01), so a decrease in temperature alone cannot account for sublimation cessation, thus disintegration or material exhaustion may be more plausible. In order to test our hypotheses we propose to observe P/2020 MK4 with the WFC3 instrument with the F350LP filter in a sequence of four images acquired during a single orbit. With these observations we will (1) search for the presence of a nucleus (or nuclei, in case of breakup), (2) characterize the activity morphology, (3) measure the size of the debris cloud, and (4) describe the changes in mass loss rates through an observationally informed model of our own construction. In addition to furthering our understanding of active Centaurs, our findings will significantly enhance our understanding of the Centaur population if a fraction of the objects vanish prior to discovery, a possibility enhanced by their recent arrival to the Centaur region and short dynamical lifetimes. We request 4 X 432 s WFC3 exposures with the F350LP filter, all within a single orbit (though our science can be carried out with observations spanning multiple orbits if necessary). The target is P/2020 MK4, and it should be tracked non-siderealy. Dr. Chandler is an expert in minor planet cometary activity, including active Centaurs such as the object targeted by this proposal. Dr. Trujillo has expertise in working with HST data and products, including four publications stemming from data analysis of HST observations. Dr. Oldroyd is an expert in solar system dynamics and has expertise in modeling that will supplment our analysis. Dr. Tegler and Dr. Romanishin are experts in the photometric study of Centaurs. Solar System Astronomy 0 false SUPPORTED SOLAR SYSTEM YES COMET P/2020 MK4 TYPE=COMET,Q=6.023599722627209,E=0.02054475958444175,I=6.691382147221793 ,O=1.888050999838472,W=169.9937011228537,T=06-MAY-2015:10:29:43,TTimeScale=TDB,EQUINOX=J2000,EPOCH=07-SEP-2020:00:00:00,EpochTimeScale=TDB EARTH WFC3/UVIS Imaging No No F350LP POS-TARG DITHER 0.173 LINE 0.112 false false 81.785 4 23.884 WFC3-UVIS-DITHER-BOX 2 false 1671833581171 Using ephemeris for target 17291-01-COMET-P-2020-MK4 ephemeris data for target 17291-01-COMET-P-2020-MK4 does not cover planning interval. Physical constraints are assumed to be unschedulable outside of the ephemeris data. Planning interval: 22.213 to 24.182. ephemeris interval: 22.334 to 24.336 The scheduling data was generated by CASM 30.3. CASM was run in Phase II mode. expanded via "auto-adjust" to 432 s each to maximize usable time of orbit (Tic-Visit :proposal-id 17291 :visit-id "01" :proposal-version -1 :trans-version "20220630" :date "23-Dec-2022 17:13:00.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 1 :saa-model "29" :si-bright-earth-limb-angle 20.0 :data-volume 1154992 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 17291 :visit-id "01" :obset-id "01" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 17291 :visit-id "01" :orbit-number 1 :pcs-time 393 :si-vis-utilization 2166 :al-overhead-at-end 0 :internal-dur-at-end 668 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 2782 :pcs-gap 0 ) true 1 0