Cannot find file /Users/jewitt/Dropbox/Cycle27_2017K2/Cycle27_K2.pdf0Assigned ID: 138
----- Attempting Submission 1 (Wed Apr 03 16:55:24 GMT 2019) -----
HST Phase I Proposal 138 (Cycle27_K2_AS_SUBMITTED.pdf.apt) successfully submitted.
Receipt: # 138-1
----- Attempting Submission 2 (Wed Apr 03 16:57:32 GMT 2019) -----
HST Phase I Proposal 138 (Cycle27_K2_AS_SUBMITTED.pdf.apt) successfully submitted.
Receipt: # 138-2
----- Attempting Submission 3 (Thu Apr 04 23:11:29 GMT 2019) -----Could not find ephemeris for target 15973-05-C2017K2-V5In this resubmission I have created a new K2 target with updated orbital elements from JPL Horizons, and used it for the final visit 05. I also adjusted the BETWEEN windows for visit 05 to avoid spoiler stars. Thanks for the reminder, Alison! -- Max Mutchler-1923685926----- Attempting Submission 1 (Sat Jul 06 18:00:13 GMT 2019) -----
----- Attempting Submission 2 (Tue Nov 19 16:58:08 GMT 2019) -----
----- Attempting Submission 3 (Tue Feb 25 16:22:44 GMT 2020) -----
----- Attempting Submission 4 (Tue Feb 25 17:58:18 GMT 2020) -----
----- Attempting Submission 5 (Tue May 26 18:57:21 GMT 2020) -----
----- Attempting Submission 6 (Thu Aug 06 15:10:36 GMT 2020) -----For some reason the Visit Planner won't compute the planning windows for 05, but I don't think anything is wrong with the target or visit.Distant Comet C/2017 K2Extraordinary long-period comet C/2017 K2 offers our best opportunity to study the rise of activity in a body entering the solar system from Oort cloud distances. Active initially at 26 AU, the comet is now near 12 AU and about to cross the critical distance for the onset of crystallization in amorphous ice. It is far too cold for any aspect of the activity to be driven by normal sublimation processes in the presumed dominant volatile, water ice. We seek HST observations 1) to measure the 3D morphology of the coma and to search for jet activity associated with crystallization 2) to photometrically isolate the nucleus from its massive coma background and so to estimate its size and 3) to contribute to a unique record of cometary development from the largest distances. Already bright beyond Saturn, K2 will cross both the crystallization zone (10 AU) and the water ice sublimation zone (5 AU) on its way to perihelion at 1.8 AU in late 2022. It is predicted to exceed naked-eye visibility and will be suited to increasingly intense astronomical study using the full range of techniques and wavelengths. It offers a unique opportunity to understand the degree to which comets evolve even before entry into the terrestrial planet region where they are more normally studied.We request 5 visits with WFC3 to study K2 crossing the crystallization zone. Observations of this unique target will be the first to test for the role of crystallization in any comet. WFC3/UVIS and the F350LP filter provide maximum sensitivity to faint and structured emission. In each orbit, we will obtain 6 images each of 260s duration, with a dither between groups of three to reject hot pixels and cosmic ray hits. Combination of the images allows the elimination of essential all cosmic ray tracks that otherwise would compromise the measurements. In order to optimally extract information about the dust coma of K2, we plan measurements as follows.
Visit 1 is scheduled as early as possible to assess the initial state of the comet, and will permit comparisons with existing imaging data. Visit 2 observes the comet as the Earth crosses its orbit plane from north to south. This in-plane geometry provides special sensitivity to the largest particles, whose low ejection speeds confine them to the cometary orbit plane, giving a line-line tail or trail appearance. The thickness of this line is a direct measure of the ejection speed, and a primary constraint on the ejection mechanism. Visit 3 is timed to image K2 from the largest angle below the orbital plane. This provides the best perspective on the distribution of material in the plane, and we expect to detect the first fan-like tail in K2 owing to ongoing mass-loss. New material from crystallization activity will reveal itself by its spatial distribution in the plane (c.f. Finson & Probstein 1968). Visit 4 again records the comet from its orbital plane but as the Earth moves from south to north. Comparison with Visit 2 will allow us to assess changes in the intervening 6 months from exactly the same viewing angle. In this time K2 moves from rH = 10.2 AU to 8.9 AU, prime distance for activity driven by crystallization. Final Visit 5 occurs from the maximum angle above the orbital plane, providing a stereo view when compared with Visit 3. This combination of times and angles will give us maximum leverage in the application of our dust dynamics model, needed to extract fundamental parameters of the coma.
Our observing strategy is to take WFC3 exposures using a wide bandpass filter (F350LP) for maximum sensitivity. The predicted brightness of a 9 km nucleus at 12 AU is V = 22 which, without the coma, would be an easy measurement. However, given the presence of the massive coma, the nucleus cannot be isolated without the fine resolution and PSF stability of HST needed to disentangle the nucleus from the coma. The apparent rates of non-sidereal motion remain easily within Hubble's tracking capabilities and also slow enough to keep a single pair of guide stars within the FGS pickles for an entire visibility window. The ephemeris uncertainty of K2 is negligible because it is a long-observed object. Ephemeris issues are of no concern to this proposal. We understand that we will have essentially no control over the spacecraft roll angle, which means we will not be able to optimize the orientation of any dust tail on the CCD (i.e., to orient a 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 no matter what spacecraft roll angle is used.The team has expertise in all aspects of the program, including physics of active asteroids, origin of active asteroids, dynamics of dust under the action of radiation and gravity, operational details of HST, reduction and analysis of WFC3 data and prompt publication of the data. 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 19 refereed papers based on Hubble data. Max Mutchler is an expert in planning the aquisition of HST data and interpreting its properties. Jessica Agarwal and Yoonyoung Kim are experts in modeling the dynamics of dust under the combined action of solar gravity and radiation pressure, with experience in the application to many comets. Jing Li is experienced in CCD data reduction techniques. Harold Weaver is a long-term user of HST with experience in all aspects of its operation. We will all work to promptly write the papers.Solar System6falsefalsefalsefalsefalsefalsefalseSUPPORTEDSOLAR SYSTEMYESCOMETdistant cometTYPE=COMET,Q=1.808218882175621,E=1.000358260337378,I=87.54744458634227
,O=88.23491101383877,W=236.0474261597543,T=20-DEC-2022:23:34:34,TTimeScale=TDB,EQUINOX=J2000,EPOCH=24-APR-2018:00:00:00,EpochTimeScale=TDBEARTHSOLAR SYSTEMYESCOMETdistant cometTYPE=COMET,Q=1.806744822544937,E=1.000357930157462,I=87.54491480043235
,O=88.25182687379407,W=236.0649075500748,T=20-DEC-2022:19:19:53,TTimeScale=TDB,EQUINOX=J2000,EPOCH=14-AUG-2018:00:00:00,EpochTimeScale=TDBEARTHSOLAR SYSTEMYESCOMETdistant cometTYPE=COMET,Q=1.80642808592438,E=1.000361158009129,I=87.54465043083408
,O=88.25348410391007,W=236.0685924553383,T=20-DEC-2022:18:17:48,TTimeScale=TDB,EQUINOX=J2000,EPOCH=06-SEP-2018:00:00:00,EpochTimeScale=TDBEARTHSOLAR SYSTEMYESCOMETdistant cometTYPE=COMET,Q=1.805556561985431,E=1.000363079426984,I=87.54398267530995
,O=88.25737988381947,W=236.0793389386575,T=20-DEC-2022:15:44:07,TTimeScale=TDB,EQUINOX=J2000,EPOCH=20-NOV-2018:00:00:00,EpochTimeScale=TDBEARTHSOLAR SYSTEMYESCOMETdistant cometTYPE=COMET,Q=1.80438697343485,E=1.000368117470132,I=87.54208101109985
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