0 Increased teh spacing between the visits so that is just fits in before December 12 -1075117480 ----- Attempting Submission 1 (Tue Apr 02 08:55:22 GMT 2024) ----- ----- Attempting Submission 2 (Thu Dec 05 14:13:08 GMT 2024) ----- ----- Attempting Submission 3 (Tue Oct 07 05:30:06 GMT 2025) ----- ----- Attempting Submission 4 (Wed Oct 22 10:13:10 GMT 2025) ----- Measuring the Hubble constant with the next multiple-imaged lensed supernova Spectroscopic time-delay measurements of multiply-imaged supernovae offer a very efficient way to measure the expansion rate of the universe. NIRCam and NIRSpec follow-up observations with JWST upon the next lensed supernova (SN) discovered by the Zwicky Transient Facility (ZTF) or the La Silla Schmidt Southern Survey (LS4) could pave the way for a novel technique to measure the Hubble constant and adress the "Hubble tension". Unlike any other time-delay measurement, spectroscopic dating of multiple SN images can be done without repeated observations. We propose to select a suitable lensed supernova for ToO observations and anticipate a 5% (or better) measurement of H0, with only 3.5 hours of JWST time. Target of opportunity imaging observations of a confirmed lensed SN. Three optical filters and one NIR. The PI and Co-I's time experience in transient surveys leading to HST follow-up observations and analysis of Type Ia supernovae, both in the local universe (e.g., SN2014J) and at high redshifts, most notably iPTF16geu and SNZwicky, the two strongly lensed SNIa observed with HST. The team members have access to proprietary ZTF and LS4 data, beyond the public survey, as well as significant ground based spectroscopic resources needed for candidate vetting, as well as the PI of the Ampel broker, specialized in early transient discoveries with ZTF. The co-investigators have a track record of over 35 successful HST programs. We also have lens modeling expertise among the Co-I's. ZTF SN Search expertise: Our team is entirely made of ZTF SN scientists. In particular, co-I's Nordin is the lead author of the Ampel broker specializing in early SN detections and Andreoni has developed an efficient SN search pipe-line also including proprietary Caltech observations, Co-I's Sagues Carracedo and Townsend have developed tools for fast vetting of SN candidates, needed for identifying candidates for spectroscopic screening. Co-I's Kenworthy and Thorp have developed novel methods to fit the SN data that are important for the data analysis connected to this program. Rigault, Smith and Schulze are key members of the ZTF SN search and ground based follow-up. LS4:Co-I Nugent is leading the supernova search effort on LS4. Spectroscopic screening: Co-I's Yan, Fremling (Palomar, Keck), Andreoni (Gemini) and Goobar (VLT-Muse) have a good track record of getting spectroscopy follow-up time needed to vet lensed SN candidates. Keck-AO screening: CO-I's Yan and Fremling have access to Keck AO that can help to identify a suitable candidate. Space SN data: The PI and co-I's Dhawan and Johansson developed the tools to observe iPTF16geu and SNZwicky. The PI has an accepted HST ToO program that could complement the proposed JWST program. Lens modelling: Co-I's Mortsell and Arendse led the lensing analysis of SNZwicky and have tools ready to re-use for the next SN. Co-I's Collett and Graham are experts in gravitational lensing JWST expertise: Adamo, Claeissens, Rivera-Thorsen and Johansson have succesfully analysed Cycle 1 JWST data. Galaxies Large Scale Structure of the Universe 6 false false false false false false SUPPORTED STAR GRAVITATIONAL LENS SUPERNOVA Transient in the ZTF survey in a known galaxy-scale lensing candidate system (lens at z=0.3754) . Liverpool telescope images from Oct 3 and 4 revelaled two additional fainter images, indicating the lensing nature of the transient. ZTF25ABNJZNP J2000 WFC3/IR Imaging No No F160W WFC3/UVIS Imaging No No F475W WFC3/UVIS Imaging No No F625W WFC3/UVIS Imaging No No F814W WFC3/IR Imaging No No F160W WFC3/UVIS Imaging No No F475W WFC3/UVIS Imaging No No F625W WFC3/UVIS Imaging No No F814W POS-TARG DITHER 1.305 LINE false false 3 41.788 WFC3-IR-DITHER-LINE-3PT 1 false POS-TARG DITHER 0.135 LINE false false 3 46.84 WFC3-UVIS-DITHER-LINE-3PT 2 false Timing link suitability includes constraints ([02 After 01 by 40.0 to 53.0 days]) The scheduling data was generated by CASM 33.1. CASM was run in Phase II mode. 1760983387000 290.0 (Tic-Visit :proposal-id 17611 :visit-id "01" :proposal-version -1 :trans-version "20250624" :date "07-Oct-2025 07:16:53.0" :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 191152 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 17611 :visit-id "01" :obset-id "01" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 17611 :visit-id "01" :orbit-number 1 :pcs-time 380 :si-vis-utilization 2480 :al-overhead-at-end 0 :internal-dur-at-end 290 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 2868 :pcs-gap 0 ) true 1 0 This is a generic target in ToO mode Timing link suitability includes constraints ([02 After 01 by 40.0 to 53.0 days]) The scheduling data was generated by CASM 33.1. CASM was run in Phase II mode. (Tic-Visit :proposal-id 17611 :visit-id "02" :proposal-version -1 :trans-version "20250624" :date "07-Oct-2025 07:16:53.0" :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 191152 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 17611 :visit-id "02" :obset-id "02" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 17611 :visit-id "02" :orbit-number 1 :pcs-time 380 :si-vis-utilization 2480 :al-overhead-at-end 0 :internal-dur-at-end 290 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 2868 :pcs-gap 0 ) true 1 0 This is a generic target in ToO mode