0 Assigned ID: 6400 ----- Attempting Submission 1 (Thu Apr 10 09:26:18 GMT 2025) ----- HST Phase I Proposal 6400 successfully submitted. Receipt: # 6400-1 ----- Attempting Submission 2 (Thu Apr 10 22:34:21 GMT 2025) ----- This is the third submission of our Phase II. We have removed the non-interrupible sequences and replaced them with a functionally equivalent series of 6 exposures. Phase II submission 1. I have updated the ephemerides for my targets. Each observation consists of 6 x 300 s exposures. I used no gyro bias update for my observations. I have added timing windows to avoid when bright stars are going to be in the path of my targets. I have added a 6 point small pos targ dither pattern to my observations. I have run the orbit and visit planner to ensure that my observations are schedulable in 2025 February for 336756 and in 2025 March for 523797. Can you please check these observations and let me know if you have comments on them? Thank you, Bryce -1635421982 ----- Attempting Submission 1 (Tue Jul 29 23:59:26 GMT 2025) ----- ----- Attempting Submission 2 (Wed Aug 13 21:53:21 GMT 2025) ----- ----- Attempting Submission 3 (Wed Aug 27 23:06:20 GMT 2025) ----- The vast majority of comets show maximum amounts of activity when they cross the ice sublimation line between 4-5 au. Bodies that show activity beyond the ice sublimation line are thought to be driven by the sublimation of hypervolatiles such as CO2 and CO, which begin to sublimate well beyond 10 au. Recently, a class of objects known as distantly active comets, such as long-period comets C/2017 K2 and C/2014 UN271, and Centaur 95P/Chiron, have shown activity well beyond this distance, strongly supporting the hypervolatile activity hypothesis. However, additional examples of distantly active comets are rare. In this proposal, we have identified two candidate comets located more than ~20 au from the Sun and show evidence of being active by having significant non-gravitational accelerations. We propose to use the exceptional sensitivity and angular resolution of HST/WFC3 to test or set stringent limits on the activity of two distantly active comet candidates, (336756) 2010 NV1 and (523797) 2016 NM56. Our observations will test these candidate comets' activity by using the high sensitivity and resolution of HST to constrain their extendedness relative to point sources and mass loss below the limit implied by their non-gravitational accelerations. By testing these candidates for distant activity, we will dramatically increase the sample of distantly active comets, which will be used to test the predictions of planet formation models used to describe the formation and early evolution of cometary bodies in the solar system. We will acquire images in the F350LP filter for a maximum throughput of a Solar-like source, which is expected for our targets. Each visit will consist of six 320-s exposures using the F350LP filter and the UVIS2-C1K1C-SUB detector setup for a total integration time of 1920 s. The UVIS2-C1K1C-SUB is used because it provides a field of view large enough to contain our targets, which all have ephemeris uncertainties of less than 1 arcsec and have a low data volume to allow us to take six exposures without a serial dump penalty. Each of our visits will only consist of a single orbit. Therefore, we will not need to use a gyro bias update. The F350LP filter provides the maximum throughput enabled by WFC3/UVIS in the 300 nm - 800 nm wavelength range for a Solar-like source expected of solar system objects while allowing for a 0.04 pixel scale. We will use the methodology of Jewitt et al. 2020 for color calibrations of the F350LP filter observations. We will use line dithering to reduce the noise from flat-field calibration errors, cosmic rays, and residual images. The team comprises members with extensive experience in high-contrast, comet observing, modeling, and data analysis from space-based observations. The entire team will be involved with the JWST observations, reducing the data, interpreting the results, and rapid turnaround in preparing scientific publications. The PI, Dr. Bryce Bolin (Goddard), has extensive experience in observing comets and reducing comet data, contributing to several comet-related publications. Dr. James Bauer (UMD) is an expert at space-based observations of comets, nucleus extraction, size estimation, and determining activity production rates, including activity measurements from NEOWISE W2 band observations of 2I/Borisov. Dr. Ian Wong (Goddard) is an expert in ground and space-based observations of primitive asteroids and trans-Neptunian bodies, reduction, and interpretation of spectral and imaging data. Dr. Dean Hines (STScI) is an expert on spacecraft observations of comets, cometary dust's physical and spectral properties, and the reduction of spacecraft image data. Ms. Laura-May Abron (GO) is an expert on analyzing images of faint solar system objects. Dr. Keith Noll (Goddard) is an expert observer of distant solar system bodies using ground and space observatories and analyzing distant object surface features, binaries, and physical properties. Dr. Christine Chen (JHU) is an expert observer who uses space-based assets in multiple platforms and wavelength regimes to maximize the observations' effectiveness. Drs. Yan Fernandez (UCF) and Carey M. Lisse (APL) are experts on comet observations with decades of experience in observing cometary nuclei and their emitted dust & gas from ground-based and space-based observatories such as Chandra, Spitzer, HST, and Deep Impact. Prof. Alessandro Morbidelli (OCA) is an expert on the dynamics and origins of small-body populations and the interpretation of observational and cosmochemical data. Dr. Ludmilla Kolokolova (UMD) is Principal Research Scientist at the Small Bodies group, University of Maryland. She is an expert in light scattering by surfaces and dust particles. Her major experience is in the computer modeling of photometric and polarimetric characteristics of the solar system objects with a focus on comets and satellites, skills which are required for the interpretation of the observations of Jupiter Trojans. Solar System Astronomy 6 false false false false false false SUPPORTED SOLAR SYSTEM YES COMET distant comet TYPE=COMET,Q=9.418643768523664,E=0.969512448983736,I=140.8078454726423 ,O=136.1979282539766,W=132.9680938874039,T=14-DEC-2010:12:00:53,TTimeScale=TDB,EQUINOX=J2000,EPOCH=22-JUN-2013:00:00:00,EpochTimeScale=TDB EARTH SOLAR SYSTEM YES COMET distant comet TYPE=COMET,Q=10.52698864463187,E=0.8578637261172851,I=144.0483239884555 ,O=350.0186370149513,W=345.6683665580405,T=14-OCT-2015:02:49:09,TTimeScale=TDB,EQUINOX=J2000,EPOCH=22-NOV-2015:00:00:00,EpochTimeScale=TDB EARTH WFC3/UVIS Imaging No No F350LP WFC3/UVIS Imaging No No F350LP 1756335837788 /private/var/folders/ms/fpqqs1dx5v5g139hcz1v6m2h0000gp/T/OPVisit6694659381320551064.xml The scheduling data was generated by CASM 33.1. CASM was run in Phase II mode. (Tic-Visit :proposal-id 18071 :visit-id "01" :proposal-version -1 :trans-version "20250624" :date "27-Aug-2025 16:03:57.0" :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 106960 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 18071 :visit-id "01" :obset-id "01" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 18071 :visit-id "01" :orbit-number 1 :pcs-time 380 :si-vis-utilization 2598 :al-overhead-at-end 0 :internal-dur-at-end 153 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 2979 :pcs-gap 0 ) true 1 0 1756335841920 /private/var/folders/ms/fpqqs1dx5v5g139hcz1v6m2h0000gp/T/OPVisit1373469630878871599.xml The scheduling data was generated by CASM 33.1. CASM was run in Phase II mode. (Tic-Visit :proposal-id 18071 :visit-id "02" :proposal-version -1 :trans-version "20250624" :date "27-Aug-2025 16:04:01.0" :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 106960 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 18071 :visit-id "02" :obset-id "02" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 18071 :visit-id "02" :orbit-number 1 :pcs-time 380 :si-vis-utilization 2598 :al-overhead-at-end 0 :internal-dur-at-end 153 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 2979 :pcs-gap 0 ) true 1 0