0 Assigned ID: 1115 ----- Attempting Submission 1 (Wed Jul 08 16:27:47 GMT 2020) ----- HST Phase I Proposal 1115 successfully submitted. Receipt: # 1115-1 SAME POS MAY NOT BE APPROPRIATE SAME POS MAY NOT BE APPROPRIATE FLASH level may be too low for this exposure or a short subexposure. See extended explanation in the diagnostic browser FLASH level may be too low for this exposure or a short subexposure. See extended explanation in the diagnostic browser FLASH level may be too low for this exposure or a short subexposure. See extended explanation in the diagnostic browser FLASH level may be too low for this exposure or a short subexposure. See extended explanation in the diagnostic browser FLASH level may be too low for this exposure or a short subexposure. See extended explanation in the diagnostic browser FLASH level may be too low for this exposure or a short subexposure. See extended explanation in the diagnostic browser FLASH level may be too low for this exposure or a short subexposure. See extended explanation in the diagnostic browser FLASH level may be too low for this exposure or a short subexposure. See extended explanation in the diagnostic browser FLASH level may be too low for this exposure or a short subexposure. See extended explanation in the diagnostic browser FLASH level may be too low for this exposure or a short subexposure. See extended explanation in the diagnostic browser SAME POS MAY NOT BE APPROPRIATE SAME POS MAY NOT BE APPROPRIATE SAME POS MAY NOT BE APPROPRIATE SAME POS MAY NOT BE APPROPRIATE SAME POS MAY NOT BE APPROPRIATE SAME POS MAY NOT BE APPROPRIATE SAME POS MAY NOT BE APPROPRIATE FLASH level may be too low for this exposure or a short subexposure. See extended explanation in the diagnostic browser FLASH level may be too low for this exposure or a short subexposure. See extended explanation in the diagnostic browser FLASH level may be too low for this exposure or a short subexposure. See extended explanation in the diagnostic browser FLASH level may be too low for this exposure or a short subexposure. See extended explanation in the diagnostic browser FLASH level may be too low for this exposure or a short subexposure. See extended explanation in the diagnostic browser FLASH level may be too low for this exposure or a short subexposure. See extended explanation in the diagnostic browser FLASH level may be too low for this exposure or a short subexposure. See extended explanation in the diagnostic browser 1. Initial submission 2. Increased dither for second exposure group in visit 2 to dither over WFC3 chip gap 3. Reduced parallel exposure lengths (replaced F775W+CLR with another F775W+POL in orbit 1, and split an F775W exposure in orbit 2); updated ephemeris; updated post-args; relaxed timing constraints 4. Adjusted timing constraints 5. Adjusted apertures and pos targs to reduce pointing movement; added FLASH to F373N; adjusted exposure lengths to compensate for changes; updated ephemeris -847007368 ----- Attempting Submission 1 (Fri Jul 17 18:43:02 GMT 2020) ----- HST Phase II Proposal 16418 successfully submitted. Receipt: # 16418-1 ----- Attempting Submission 2 (Fri Jul 17 19:01:25 GMT 2020) ----- HST Phase II Proposal 16418 successfully submitted. Receipt: # 16418-2 ----- Attempting Submission 3 (Fri Jul 17 20:47:02 GMT 2020) ----- HST Phase II Proposal 16418 successfully submitted. Receipt: # 16418-3 ----- Attempting Submission 4 (Fri Jul 17 20:57:34 GMT 2020) ----- ----- Attempting Submission 5 (Mon Jul 20 02:05:12 GMT 2020) ----- FLASH: The dust in the coma/tail should mostly provide a sufficient "flash" over the full frame already. SAME POS: Pointing does not need to be exact, so ACS polarizer distortions shifting the target slightly between these exposures is acceptable. C/2020 F3 (NEOWISE) is the brightest near-Sun comet to survive perihelion in over a decade, and since its post-conjunction recovery from the ground in early 2020 July, has displayed a morphology that is characteristic of many of the brightest and most active such comets in history. Moreover, C/2020 F3 features post-perihelion observing geometry that is unusually favorable for a near-Sun comet, leaving the 55 degree solar exclusion zone of HST only one month past perihelion. These factors combine to make this comet not only a target likely to have high public awareness, but also a particularly favorable candidate for close study to evaluate the behavior and evolution of comets near the Sun more generally. We propose to use WFC3/UVIS and ACS/WFC to collect multi-color imagery and imaging polarimetry of C/2020 F3 to trace the spatial variation of dust properties throughout the coma---particularly of its jets---and characterize or constrain the presence of fragments or unresolved debris streams produced by the earlier intense activity near perihelion. These observations will provide the first high resolution look at the effects of perihelic heating on a surviving near-Sun comet, and with the imminent loss of HST's three gyro mode and the corresponding collapse in its field of regard, will likely be the last opportunity of this favorability to conduct such analysis for the foreseeable future. We request two orbits to conduct color imaging and polarimetry of C/2020 F3. As the comet will be receding from the Sun and the targeted activity rapidly declining during the observing window, the observations should be ideally scheduled as early as possible, once the comet leaves the 55 degree solar exclusion zone on 2020 August 3. Orbit 1 will use WFC3/UVIS to image the comet through five filters: F373N, F487N, F689M, F775W, and F845M. These filters were selected to minimize the contamination of dust colors by typical strong cometary emission lines. Two dithered frames will be collected through each filter to protect against passing field stars, cosmic rays, and detector defects. To avoid a serial buffer dump, the F487N, F689M, and F845M frames will be limited to a 1k subarray, which will provide a 40'' wide field of view---still sufficient to cover the inner coma. F373N and F775W will be recorded on the full UVIS frame in order to provide the widest possible field of view (2.7') to search for fragments. Orbit 2 will use ACS/WFC to image the comet through F775W crossed with each of the POL0V, POL60V, and POL120V polarizers. The limited ACS buffer size and inability to use <2k subarrays with polarizers limits this orbit to three dithered triplets of POL0V+POL60V+POL120V exposures. The first triplet will be comprised of very short exposures to avoid saturation, as described above, while the other two will be longer exposures to improve sensitivity to fainter structures and fragments. An unsaturated F775W+CLR exposure will also be included to protect the polarimetry of the near-nucleus region (likely saturated in the other two polarizer triplets) from stars, cosmic rays, and detector defects. We expect to measure polarizations in the range 10--40%, and with this exposure structure, we anticipate having sufficient S/N for the measured coma polarization to be calibration-limited over most of the frame. We additionally request coordinated parallel observations with ACS in orbit 1 and WFC3 in orbit 2. These observations will further constrain or characterize the presence of fragments away from the coma, as well any other spatially small features in the dust (including from the disintegration of unresolved fragments) that cannot be resolved from the ground as well as improve the precision of colors/polarimetry measured in the lower surface brightness outer regions of the coma by the primary observations, where sky background contamination could be important. Q. Zhang is experienced in observing and characterizing small bodies in the solar system, and led a recent HST/ACS polarimetry program targeting interstellar comet 2I/Borisov (HST GO 16044). He was involved with the observational and theoretical characterization of interstellar object 1I/`Oumuamua (e.g., Zhang 2018, ApJL, 852, L13), and is familiar with the behavior of small bodies under solar irradiation, including from his work with the Sungrazer project characterizing the orbits and morphology of near-Sun objects with space-based telescopes. Dr. Ye has led and/or participated in a number of ground-based or HST-involved projects on small solar system bodies, such as (3200) Phaethon (HST GO 15357, PI Q. Ye; Ye et al. 2018, ApJL, 864, 9), (6478) Gault (Ye et al. 2019, ApJL, 874, 16), and 1I/`Oumuamua (Ye et al. 2017, ApJL, 851, 5). His area of expertise is in the analysis of visible and infrared imaging of comets and asteroids, as well as in planetary dynamics. Dr. Kolokolova is an expert in photopolarimetric studies of cosmic dust, specifically cometary dust and asteroid regolith. Her main interest is interpretation of the photometric and polarimetric data using computer modeling of light scattering by dust particles, thus revealing their size, shape, structure, and composition. As the archive manager of the PDS Small Bodies Node, she is well familiar with ground-based and space data resulting from observations of comets and asteroids. Prof. Knight is a world expert in near-Sun comets with nearly two decades of experience studying their morphology, photometry, and dynamics. He has conducted numerous investigations, participated in international teams, and co-authored two review papers about near-Sun comets. He is also a highly experienced optical observer who has analyzed dust and gas coma morphology on hundreds of nights of comet data. Prof. Hallinan is an expert in time domain astronomy, and has spearheaded and supervised numerous instrumentation and observing programs targeting time varying sources at frequencies across the electromagnetic spectrum both from the ground and from space. Solar System Astronomy 0 false SUPPORTED SOLAR SYSTEM YES COMET C/2020 F3 (NEOWISE) TYPE=COMET,Q=0.2946512619109637,E=0.99916958479388,I=128.937400236612 ,O=61.00942236569867,W=37.2784724513936,T=03-JUL-2020:16:17:50,TTimeScale=TDB,EQUINOX=J2000,EPOCH=03-AUG-2020:00:00:00,EpochTimeScale=TDB EARTH WFC3/UVIS Imaging No No F373N WFC3/UVIS Imaging No No F487N WFC3/UVIS Imaging No No F689M WFC3/UVIS Imaging No No F775W WFC3/UVIS Imaging No No F845M ACS/WFC Imaging No No F775W ACS/WFC Imaging No Yes F775W ACS/WFC Imaging No Yes F775W WFC3/UVIS Imaging No No F373N WFC3/UVIS Imaging No No F487N WFC3/UVIS Imaging No No F689M WFC3/UVIS Imaging No No F775W WFC3/UVIS Imaging No No F845M 1595202660377 Using ephemeris for target 16418-01-2020F3 ephemeris data for target 16418-01-2020F3 does not cover planning interval. Physical constraints are assumed to be unschedulable outside of the ephemeris data. Planning interval: 19.213 to 21.182. ephemeris interval: 20.182 to 22.182 Timing link suitability includes constraints ([Group (01 02) Within 0.1 days]) The scheduling data was generated by CASM 28.2. CASM was run in Phase II mode. (Tic-Visit :proposal-id 16418 :visit-id "01" :proposal-version -1 :trans-version "20200619" :date "19-Jul-2020 17:51:00.0" :trans-errors '(:WARNINGS 2 :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 1685920 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 16418 :visit-id "01" :obset-id "01" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 16418 :visit-id "01" :orbit-number 1 :pcs-time 393 :si-vis-utilization 2749 :al-overhead-at-end 0 :internal-dur-at-end 1015 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3142 :pcs-gap 0 ) false 1 0 1595199692045 Using ephemeris for target 16418-02-2020F3 ephemeris data for target 16418-02-2020F3 does not cover planning interval. Physical constraints are assumed to be unschedulable outside of the ephemeris data. Planning interval: 19.213 to 21.182. ephemeris interval: 20.182 to 22.182 Timing link suitability includes constraints ([Group (01 02) Within 0.1 days]) The scheduling data was generated by CASM 28.2. CASM was run in Phase II mode. (Tic-Visit :proposal-id 16418 :visit-id "02" :proposal-version -1 :trans-version "20200619" :date "19-Jul-2020 17:01:31.0" :trans-errors '(:WARNINGS 7 :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 1640240 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 16418 :visit-id "02" :obset-id "02" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 16418 :visit-id "02" :orbit-number 1 :pcs-time 393 :si-vis-utilization 2749 :al-overhead-at-end 0 :internal-dur-at-end 1015 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3142 :pcs-gap 0 ) false 1 0