Fixed typo in abstract. 293116065 Assigned ID: 3896 ----- Attempting Submission 1 (Sat Feb 18 02:01:36 GMT 2023) ----- HST Phase I Proposal 3896 successfully submitted. Receipt: # 3896-1 ----- Attempting Submission 2 (Sat Feb 18 02:05:03 GMT 2023) ----- 1. Initial submission 2. Increased scheduability 80 to cover June 20.5-26.5 -656726286 ----- Attempting Submission 1 (Mon Apr 10 02:18:42 GMT 2023) ----- HST Phase II Proposal 17302 successfully submitted. Receipt: # 17302-1 ----- Attempting Submission 2 (Mon Apr 10 03:41:09 GMT 2023) ----- HST Phase II Proposal 17302 failed submission. ----- Attempting Submission 3 (Mon Apr 10 03:41:39 GMT 2023) ----- Mapping the Debris of Comet 96P/Machholz Periodic sunskirting comet 96P/Machholz is the largest surviving member of a vast fragmentation complex spanning a few dozen near-Earth objects and meteoroid streams responsible for 3 major annual meteor showers on Earth. Observations by SOHO's LASCO coronagraphs show 96P's fragmentation to be ongoing, finding the comet to be accompanied by a dense trail of fragments/debris during its 2012 apparition, again one orbit later in 2017, and recently for the third time in 2023 January. However, SOHO can only see gas (largely sodium) and, to a lesser extent, dust released by the fragments, and not the actual solid bodies. This limitation hinders accurate size/mass estimates of these fragments, and indeed of any active "comet" SOHO observes, since a small but highly active fragment/comet can appear similar to a large but less active one. We propose to address this shortcoming by using HST's WFC3/UVIS to map the fragments along the debris trail while they are largely inactive away from the Sun, taking advantage of favorable geometry in late 2023 June that enables highly efficient observations. Parallel ACS/WFC observations will further enhance sensitivity to potential new fragments unseen by SOHO. The results will provide a translation between physical size and SOHO-observed activity to constrain the physical properties of these and the many similar cometary fragments seen by SOHO, and enable quantitative evaluation of the ongoing formation/evolution of 96P's fragmentation complex. We request 7 orbits to image the orbital track of 96P/Machholz with WFC3/UVIS around 2023 June 23.5 +/- 3.0. These 7 orbits target different points along the orbit, centered (1) 1 hour behind, (2) 3 hours ahead, (3) 7 hours ahead, (4) 11 hours ahead, (5) 15 hours ahead, (6) 30 hours ahead, and (7) 34 hours ahead of 96P. The precise targeted positions are set by the orbital elements of 96P for its 2023 apparition with the time of perihelion adjusted by the respective timing offsets. We use the following osculating orbital elements for 96P at epoch 2023 February 25.0 from MPEC 2023-G31: q = 0.1164278 au e = 0.9615855 i = 57.50263 deg O = 93.95363 deg w = 14.74900 deg T = 2023-01-31 02:01:44 Aside from pointing, the 7 orbits are identical with 5 full frame exposures of ~350 s through the F350LP filter, dithered to cover the interchip gap and improve robustness to detector defects. Additionally, 5 parallel exposures will be taken alongside the primary exposures using ACS/WFC through the F606W filter, of which, the first 4 frames are limited to the WFC1A-2K subarray by buffer dump requirements. Parallel exposures are intended to sample portions of space arbitrarily offset from the 96P orbit by the WFC3-ACS sky separation and do not impose further constraints on spacecraft roll. Gyro bias updates are not needed during the requested orbits, as they do not need to be consecutive. Karl Battams is an expert on small bodies near the Sun. He runs the Sungrazer citizen science project through which thousands of near-Sun comets (including 96P/Machholz's fragments) have been discovered, is PI of the SOHO/LASCO instrument with which most of those comets were found, and has led characterization of the dust/debris trail of (3200) Phaethon (e.g., Battams et al. 2020; ApJS, 246 64). Matthew 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. Quanzhi 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. Qicheng Zhang is experienced with comets and asteroids near the Sun, having used SOHO & STEREO imagery to first detect comet 96P/Machholz's dust/debris trails, as well as sodium emission from asteroid (3200) Phaethon. He has also previously led observations and analyses of comets with HST (e.g., HST GO 16214, PI Q. Zhang; Zhang et al. 2022, PSJ, 135, 1) as well as with various ground-based telescopes. Solar System Astronomy 3 false false false false false true false false SUPPORTED SOLAR SYSTEM Using 96P orbit with time of perihelion adjusted 1 hour later COMET 1 hour behind 96P TYPE=COMET,Q=0.1164278,E=0.9615855,I=57.50263,O=93.95363,W=14.74900,T=31-JAN-2023:03:01:44,TTimeScale=TDB,EQUINOX=J2000,EPOCH=25-FEB-2023:00:00:00,EpochTimeScale=TDB EARTH SOLAR SYSTEM Using 96P orbit with time of perihelion adjusted 3 hours earlier COMET 3 hours ahead of 96P TYPE=COMET,Q=0.1164278,E=0.9615855,I=57.50263,O=93.95363,W=14.74900,T=30-JAN-2023:23:01:44,TTimeScale=TDB,EQUINOX=J2000,EPOCH=25-FEB-2023:00:00:00,EpochTimeScale=TDB EARTH SOLAR SYSTEM Using 96P orbit with time of perihelion adjusted 7 hours earlier COMET 7 hours ahead of 96P TYPE=COMET,Q=0.1164278,E=0.9615855,I=57.50263,O=93.95363,W=14.74900,T=30-JAN-2023:19:01:44,TTimeScale=TDB,EQUINOX=J2000,EPOCH=25-FEB-2023:00:00:00,EpochTimeScale=TDB EARTH SOLAR SYSTEM Using 96P orbit with time of perihelion adjusted 11 hours earlier COMET 11 hours ahead of 96P TYPE=COMET,Q=0.1164278,E=0.9615855,I=57.50263,O=93.95363,W=14.74900,T=30-JAN-2023:15:01:44,TTimeScale=TDB,EQUINOX=J2000,EPOCH=25-FEB-2023:00:00:00,EpochTimeScale=TDB EARTH SOLAR SYSTEM Using 96P orbit with time of perihelion adjusted 15 hours earlier COMET 15 hours ahead of 96P TYPE=COMET,Q=0.1164278,E=0.9615855,I=57.50263,O=93.95363,W=14.74900,T=30-JAN-2023:11:01:44,TTimeScale=TDB,EQUINOX=J2000,EPOCH=25-FEB-2023:00:00:00,EpochTimeScale=TDB EARTH SOLAR SYSTEM Using 96P orbit with time of perihelion adjusted 30 hours earlier COMET 30 hours ahead of 96P TYPE=COMET,Q=0.1164278,E=0.9615855,I=57.50263,O=93.95363,W=14.74900,T=29-JAN-2023:20:01:44,TTimeScale=TDB,EQUINOX=J2000,EPOCH=25-FEB-2023:00:00:00,EpochTimeScale=TDB EARTH SOLAR SYSTEM Using 96P orbit with time of perihelion adjusted 34 hours earlier COMET 34 hours ahead of 96P TYPE=COMET,Q=0.1164278,E=0.9615855,I=57.50263,O=93.95363,W=14.74900,T=29-JAN-2023:16:01:44,TTimeScale=TDB,EQUINOX=J2000,EPOCH=25-FEB-2023:00:00:00,EpochTimeScale=TDB EARTH WFC3/UVIS Imaging No No F350LP WFC3/UVIS Imaging No No F350LP WFC3/UVIS Imaging No No F350LP WFC3/UVIS Imaging No No F350LP WFC3/UVIS Imaging No No F350LP WFC3/UVIS Imaging No No F350LP WFC3/UVIS Imaging No No F350LP ACS/WFC Imaging No No F606W ACS/WFC Imaging No No F606W ACS/WFC Imaging No No F606W ACS/WFC Imaging No No F606W ACS/WFC Imaging No No F606W ACS/WFC Imaging No No F606W ACS/WFC Imaging No No F606W /tmp/OPVisit15591759405896033602.xml Using ephemeris for target 17302-01-96P-FIELD1 ephemeris data for target 17302-01-96P-FIELD1 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: 23.090 to 25.091 The scheduling data was generated by CASM 31.0. CASM was run in Phase II mode. (Tic-Visit :proposal-id 17302 :visit-id "01" :proposal-version -1 :trans-version "20220630" :date "09-Apr-2023 19:43:55.0" :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 2012272 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 17302 :visit-id "01" :obset-id "01" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 17302 :visit-id "01" :orbit-number 1 :pcs-time 393 :si-vis-utilization 2580 :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 2973 :pcs-gap 0 ) true 1 0 /tmp/OPVisit11834255223650599496.xml Using ephemeris for target 17302-02-96P-FIELD2 ephemeris data for target 17302-02-96P-FIELD2 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: 23.090 to 25.091 The scheduling data was generated by CASM 31.0. CASM was run in Phase II mode. (Tic-Visit :proposal-id 17302 :visit-id "02" :proposal-version -1 :trans-version "20220630" :date "09-Apr-2023 19:49:42.0" :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 2012272 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 17302 :visit-id "02" :obset-id "02" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 17302 :visit-id "02" :orbit-number 1 :pcs-time 393 :si-vis-utilization 2580 :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 2973 :pcs-gap 0 ) true 1 0 /tmp/OPVisit7554132023768561628.xml Using ephemeris for target 17302-03-96P-FIELD3 ephemeris data for target 17302-03-96P-FIELD3 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: 23.090 to 25.091 The scheduling data was generated by CASM 31.0. CASM was run in Phase II mode. (Tic-Visit :proposal-id 17302 :visit-id "03" :proposal-version -1 :trans-version "20220630" :date "09-Apr-2023 19:49:51.0" :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 2012272 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 17302 :visit-id "03" :obset-id "03" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 17302 :visit-id "03" :orbit-number 1 :pcs-time 393 :si-vis-utilization 2580 :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 2973 :pcs-gap 0 ) true 1 0 /tmp/OPVisit9339713921629469723.xml Using ephemeris for target 17302-04-96P-FIELD4 ephemeris data for target 17302-04-96P-FIELD4 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: 23.090 to 25.091 The scheduling data was generated by CASM 31.0. CASM was run in Phase II mode. (Tic-Visit :proposal-id 17302 :visit-id "04" :proposal-version -1 :trans-version "20220630" :date "09-Apr-2023 19:50:11.0" :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 2012272 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 17302 :visit-id "04" :obset-id "04" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 17302 :visit-id "04" :orbit-number 1 :pcs-time 393 :si-vis-utilization 2580 :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 2973 :pcs-gap 0 ) true 1 0 /tmp/OPVisit3372645981851840041.xml Using ephemeris for target 17302-05-96P-FIELD5 ephemeris data for target 17302-05-96P-FIELD5 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: 23.090 to 25.091 The scheduling data was generated by CASM 31.0. CASM was run in Phase II mode. (Tic-Visit :proposal-id 17302 :visit-id "05" :proposal-version -1 :trans-version "20220630" :date "09-Apr-2023 19:49:55.0" :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 2012272 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 17302 :visit-id "05" :obset-id "05" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 17302 :visit-id "05" :orbit-number 1 :pcs-time 393 :si-vis-utilization 2580 :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 2973 :pcs-gap 0 ) true 1 0 /tmp/OPVisit9469567599850137205.xml Using ephemeris for target 17302-06-96P-FIELD6 ephemeris data for target 17302-06-96P-FIELD6 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: 23.090 to 25.091 The scheduling data was generated by CASM 31.0. CASM was run in Phase II mode. (Tic-Visit :proposal-id 17302 :visit-id "06" :proposal-version -1 :trans-version "20220630" :date "09-Apr-2023 19:49:56.0" :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 2012272 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 17302 :visit-id "06" :obset-id "06" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 17302 :visit-id "06" :orbit-number 1 :pcs-time 393 :si-vis-utilization 2580 :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 2973 :pcs-gap 0 ) true 1 0 /tmp/OPVisit6163700939084565931.xml Using ephemeris for target 17302-07-96P-FIELD7 ephemeris data for target 17302-07-96P-FIELD7 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: 23.090 to 25.091 The scheduling data was generated by CASM 31.0. CASM was run in Phase II mode. (Tic-Visit :proposal-id 17302 :visit-id "07" :proposal-version -1 :trans-version "20220630" :date "09-Apr-2023 19:49:57.0" :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 2012272 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 17302 :visit-id "07" :obset-id "07" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 17302 :visit-id "07" :orbit-number 1 :pcs-time 393 :si-vis-utilization 2580 :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 2973 :pcs-gap 0 ) true 1 0