0 Assigned ID: 6255 ----- Attempting Submission 1 (Wed Apr 09 17:51:15 GMT 2025) ----- HST Phase I Proposal 6255 successfully submitted. Receipt: # 6255-1 ----- Attempting Submission 2 (Thu Apr 10 14:53:28 GMT 2025) ----- HST Phase I Proposal 6255 successfully submitted. Receipt: # 6255-2 ----- Attempting Submission 3 (Thu Apr 10 22:21:18 GMT 2025) ----- First version of Phase 2 for 18005. If any problems arise, we are happy to adjust anything as needed. Edits made 2025-11-19: On hold removed for visits 4 and 5. Timing for these visits input as betweens. If needed, we can adjust timing requirements as needed. Edits made 2025-12-01: With the approval of an additional visit based on HOPR 93399, we have added scheduling requirements for new visit 12. It will remain on hold (with visit 06) until successful execution of visits 04 and 05. -1993364524 ----- Attempting Submission 1 (Thu Jul 24 21:16:43 GMT 2025) ----- ----- Attempting Submission 2 (Wed Nov 19 20:24:23 GMT 2025) ----- ----- Attempting Submission 3 (Mon Dec 01 18:17:47 GMT 2025) ----- 2014 WC510: A second trans-Neptunian triple? Small planetesimals in the trans-Neptunian region are thought to be formed as the result of gravitational collapse triggered by the streaming instability mechanism. Simulations of such gravitational collapses commonly produce hierarchical triple systems (and other higher multiples), suggesting that they may be common in the trans-Neptunian region. However, to date, only one hierarchical triple has been found, suggesting that either triples are rare or telescopes have not yet reached the necessary resolution to resolve them. Recent HST observations have revealed that 2014 WC510, previously seen to be a closely separated binary, could have a more distant third companion. Alternatively, the system may be a wide binary that happens to be in an edge-on orbit. To determine if WC510 is the Solar System's second confirmed hierarchical triple, we propose a simple 6 orbit program to recover the orbit of the newly discovered distant companion. This provides a sensitive test of the streaming instability formation of planetesimals. Even if not a triple system, our program will precisely measure WC510's mass, providing one of the most precisely known densities in its size range. There is also potential to predict mutual events, which can provide a powerful tool to study WC510 in exquisite detail. Our observations call for 6 single-orbit visits to image the 2014 WC510 system using the WFC3/UVIS instrument. During each visit, images will be acquired using the UVIS2-C512C-SUB aperture, paired with the F350LP filter to optimize astrometric precision. At the end of each visit, two full-frame UVIS2 images will be acquired which provides the data significant legacy value for precise absolute astrometric studies. Exposure times for all images are chosen to optimize SNR and schedulability, with 8 dithered images taken during each visit. This allows us to remain robust to unlucky cosmic ray hits. Scheduling of observations is important to the goals of our program. Recovery of binary is most efficiently accomplished by precisely timed follow-up observations. Our program begins with three "anchor" observations, which should detect the binary system at least two times. These should occur as early as possible in the Cycle and be spaced 4-8 days apart. Based on these initial detections, alongside the discovery observation, precise times for follow-up can be calculated. Hence, Visits 4-6 are placed "On hold" until after acquisition and analysis of Visits 1-3. Then, each further visit will be updated with "betweens" to efficiently recover the binary orbit. The timing windows input into the Phase II are somewhat flexible, and can be changed if necessary. If more observing windows are needed, we can provide them, although we will usually provide our "optimal" windows. Once preliminary scheduling windows are identified, we will check for bright nearby stars that could degrade image quality. PI Benjamin Proudfoot is a postdoctoral scholar at the University of Central Florida. He is an expert in orbit fitting of TNO moons and the lead developer of the MultiMoon code, which will be used to do all orbit fitting in this investigation. He has led several past studies focusing on understanding the orbits of TNO moons, including other small TNO binaries. Co-I Will Grundy is a tenured astronomer at Lowell Observatory. He has HST experience dating back to his time as a Hubble fellow in the late 1990s. He has observational experience as PI or Co-I in numerous HST programs using NICMOS, WFPC2, ACS, and WFC3 to study icy outer solar system targets, leading to publication of approximately three dozen papers in the peer-reviewed literature over the past 2 decades. He has also served on many Hubble review panels and on the Space Telescope User's Committee. Co-I Audrey Thirouin is a tenured astronomer at Lowell Observatory. She has published extensively on Kuiper belt topics including lightcurves and the prevalence of contact binaries. She led the program which discovered WC510's distant companion. Solar System Astronomy 6 false false false false false false SUPPORTED SOLAR SYSTEM NO ASTEROID TNO trinary? TYPE=ASTEROID,A=39.63878743404138,E=0.2551217183892524,I=19.54803566488891 ,O=194.5694855695911,W=288.8516732889418,M=336.7155725065204,EQUINOX=J2000,EPOCH=29-SEP-2015:00:00:00,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 POS-TARG DITHER 0.173 LINE 0.112 false false 81.785 4 23.884 WFC3-UVIS-DITHER-BOX 1 false POS-TARG DITHER 0.145 LINE false false 2 46.84 WFC3-UVIS-DITHER-LINE 2 false Using ephemeris for target 18005-01-WC510 ephemeris data for target 18005-01-WC510 does not cover planning interval. Physical constraints are assumed to be unschedulable outside of the ephemeris data. Planning interval: 25.277 to 27.120. ephemeris interval: 25.334 to 27.335 Timing link suitability includes constraints ([02 After 01 by 4.0 to 8.0 days]) The scheduling data was generated by CASM 33.1. CASM was run in Phase II mode. C:\Users\benp1\AppData\Local\Temp\OPVisit13638402454128834356.xml 1762267023000 306.3260426776403 (Tic-Visit :proposal-id 18005 :visit-id "01" :proposal-version -1 :trans-version "20250929" :date "01-Dec-2025 13:14:15.0" :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 604960 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 18005 :visit-id "01" :obset-id "01" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 18005 :visit-id "01" :orbit-number 1 :pcs-time 380 :si-vis-utilization 2466 :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 2867 :pcs-gap 0 ) true 1 0 Using ephemeris for target 18005-02-WC510 ephemeris data for target 18005-02-WC510 does not cover planning interval. Physical constraints are assumed to be unschedulable outside of the ephemeris data. Planning interval: 25.277 to 27.120. ephemeris interval: 25.334 to 27.335 Timing link suitability includes constraints ([02 After 01 by 4.0 to 8.0 days] [03 After 02 by 4.0 to 8.0 days]) The scheduling data was generated by CASM 33.1. CASM was run in Phase II mode. C:\Users\benp1\AppData\Local\Temp\OPVisit1890219247817523055.xml Should be 4-8 days after Visit 1. 1762770112000 295.0956039808983 (Tic-Visit :proposal-id 18005 :visit-id "02" :proposal-version -1 :trans-version "20250929" :date "01-Dec-2025 13:14:16.0" :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 604960 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 18005 :visit-id "02" :obset-id "02" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 18005 :visit-id "02" :orbit-number 1 :pcs-time 380 :si-vis-utilization 2466 :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 2867 :pcs-gap 0 ) true 1 0 Using ephemeris for target 18005-03-WC510 ephemeris data for target 18005-03-WC510 does not cover planning interval. Physical constraints are assumed to be unschedulable outside of the ephemeris data. Planning interval: 25.277 to 27.120. ephemeris interval: 25.334 to 27.335 Timing link suitability includes constraints ([03 After 02 by 4.0 to 8.0 days]) The scheduling data was generated by CASM 33.1. CASM was run in Phase II mode. C:\Users\benp1\AppData\Local\Temp\OPVisit11760517627064487554.xml Should be 4-8 days after Visit 2. 1763448293000 291.5818287577299 (Tic-Visit :proposal-id 18005 :visit-id "03" :proposal-version -1 :trans-version "20250929" :date "01-Dec-2025 13:14:16.0" :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 604960 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 18005 :visit-id "03" :obset-id "03" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 18005 :visit-id "03" :orbit-number 1 :pcs-time 380 :si-vis-utilization 2466 :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 2867 :pcs-gap 0 ) true 1 0 Using ephemeris for target 18005-04-WC510 ephemeris data for target 18005-04-WC510 does not cover planning interval. Physical constraints are assumed to be unschedulable outside of the ephemeris data. Planning interval: 25.277 to 27.120. ephemeris interval: 25.334 to 27.335 The scheduling data was generated by CASM 33.1. CASM was run in Phase II mode. C:\Users\benp1\AppData\Local\Temp\OPVisit6352173791696826072.xml Based on the first three visits, we have determined a range of times when the system is ideal to observe. The ideal observation date is 2025-12-23 00:00 +/- 2 days. If this timing is not possible, we can rerun our analysis and find alternate times. (Tic-Visit :proposal-id 18005 :visit-id "04" :proposal-version -1 :trans-version "20250929" :date "01-Dec-2025 13:14:17.0" :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 604960 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 18005 :visit-id "04" :obset-id "04" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 18005 :visit-id "04" :orbit-number 1 :pcs-time 380 :si-vis-utilization 2466 :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 2867 :pcs-gap 0 ) true 1 0 Using ephemeris for target 18005-05-WC510 ephemeris data for target 18005-05-WC510 does not cover planning interval. Physical constraints are assumed to be unschedulable outside of the ephemeris data. Planning interval: 25.277 to 27.120. ephemeris interval: 25.334 to 27.335 The scheduling data was generated by CASM 33.1. CASM was run in Phase II mode. C:\Users\benp1\AppData\Local\Temp\OPVisit14836933298988527629.xml Based on the first three visits, we have determined a range of times when the system is ideal to observe. The ideal observation date is 2025-12-30 12:00 +/- 2 days. If this timing is not possible, we can rerun our analysis and find alternate times. (Tic-Visit :proposal-id 18005 :visit-id "05" :proposal-version -1 :trans-version "20250929" :date "01-Dec-2025 13:14:18.0" :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 604960 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 18005 :visit-id "05" :obset-id "05" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 18005 :visit-id "05" :orbit-number 1 :pcs-time 380 :si-vis-utilization 2466 :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 2867 :pcs-gap 0 ) true 1 0 Using ephemeris for target 18005-06-WC510 ephemeris data for target 18005-06-WC510 does not cover planning interval. Physical constraints are assumed to be unschedulable outside of the ephemeris data. Planning interval: 25.277 to 27.120. ephemeris interval: 25.334 to 27.335 The scheduling data was generated by CASM 33.1. CASM was run in Phase II mode. C:\Users\benp1\AppData\Local\Temp\OPVisit6597136683435167038.xml On hold will be removed and replaced with "betweens" after acquisition and analysis of Visits 1-5. (Tic-Visit :proposal-id 18005 :visit-id "06" :proposal-version -1 :trans-version "20250929" :date "01-Dec-2025 13:14:18.0" :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 604960 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 18005 :visit-id "06" :obset-id "06" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 18005 :visit-id "06" :orbit-number 1 :pcs-time 380 :si-vis-utilization 2466 :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 2867 :pcs-gap 0 ) true 1 0 Based on the discovery observation (taken as part of program 17524) and the first five visits, optimal scheduling opportunities will be calculated and provided ASAP after Visits 1-5 are taken. These will be provided as "betweens" that last a few days. Using ephemeris for target 18005-12-WC510 ephemeris data for target 18005-12-WC510 does not cover planning interval. Physical constraints are assumed to be unschedulable outside of the ephemeris data. Planning interval: 25.277 to 27.120. ephemeris interval: 25.334 to 27.335 The scheduling data was generated by CASM 33.1. CASM was run in Phase II mode. C:\Users\benp1\AppData\Local\Temp\OPVisit10185442033508929156.xml Repeat of failed visit 02. Unfortunately, due to the failure of visit 03, less information is available about the orbit period of our target than originally planned. To remedy this, we are getting another "anchor" pair using visits 04 and 05, which should enable scheduling for the final follow-up visits (06 and 12). Scheduling for this visit will be placed on hold, as with visit 06. (Tic-Visit :proposal-id 18005 :visit-id "12" :proposal-version -1 :trans-version "20250929" :date "01-Dec-2025 13:14:19.0" :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 604960 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 18005 :visit-id "12" :obset-id "12" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 18005 :visit-id "12" :orbit-number 1 :pcs-time 380 :si-vis-utilization 2466 :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 2867 :pcs-gap 0 ) true 1 0 Based on the discovery observation (taken as part of program 17524) and the previous visits, optimal scheduling opportunities will be calculated and provided ASAP after Visits 1-5 are taken. These will be provided as "betweens" that last a few days. Backup opportunities will be available.