0 Assigned ID: 4934 ----- Attempting Submission 1 (Thu Nov 16 04:03:13 GMT 2023) ----- HST Phase I Proposal 4934 successfully submitted. Receipt: # 4934-1 ORBITAL VISIBILITY OVERRUN ORBITAL VISIBILITY OVERRUN ORBITAL VISIBILITY OVERRUN ORBITAL VISIBILITY OVERRUN ORBITAL VISIBILITY OVERRUN ORBITAL VISIBILITY OVERRUN ORBITAL VISIBILITY OVERRUN ORBITAL VISIBILITY OVERRUN ORBITAL VISIBILITY OVERRUN ORBITAL VISIBILITY OVERRUN ORBITAL VISIBILITY OVERRUN ORBITAL VISIBILITY OVERRUN 0 ----- Attempting Submission 1 (Mon Feb 19 23:04:27 GMT 2024) ----- HST Phase II Proposal 17600 successfully submitted. Receipt: # 17600-1 ----- Attempting Submission 2 (Fri Apr 19 21:06:18 GMT 2024) ----- ----- Attempting Submission 3 (Tue Oct 22 19:22:35 GMT 2024) ----- ----- Attempting Submission 4 (Tue Aug 12 21:12:19 GMT 2025) ----- ----- Attempting Submission 5 (Wed Aug 13 06:23:20 GMT 2025) ----- ----- Attempting Submission 6 (Wed Nov 19 22:50:33 GMT 2025) ----- update requested by PC The Exosphere of an Venus-Like Exoplanet We propose a 10-orbit HST/STIS Mid-Cycle program to study the exosphere of the recently discovered terrestrial exoplanet GJ 12b (TOI-6251.01). With a Venus-like radius (1.016 +/- 0.062 R_Earth) and equilibrium temperature (327 K), GJ 12b offers us a rare chance to explore important Solar System processes like the runaway greenhouse effect on an extrasolar planet. This is also the best known terrestrial planet for Lyman-alpha transit observations: GJ 12's Lyman-alpha line is likely to be intrinsically strong based on the strong stellar X-ray emission, and its close proximity (12.2 pc) and high systemic radial velocity (51.2 km/s) partially offset the (relatively weak) interstellar absorption from the stellar line core. These factors result in much higher precisions than usually achievable for exoplanet Lyman-alpha studies: with two transits of five orbits each, we expect to constrain exospheric hydrogen absorption in GJ 12b to a precision of 0.9% in the red wing of the Lyman-alpha line. At this precision we would detect a Roche-lobe-filling transit at SNR = 38.7, and we would be sensitive (at the 3-sigma level) to neutral hydrogen down to 5R_p, near the planetary exobase. By definitively confirming or ruling out exospheric hydrogen in Venus-like exoplanet, this Mid-Cycle program will significantly advance our understanding of the upper atmospheres of terrestrial exoplanets. Our program will observe two transits of GJ 12b with STIS MAMA-FUV G140M 1222A. The goal is to constrain planetary absorption in the Lyman-alpha line, i.e. to observe a decrease in the strength of the stellar LyA line during the planetary transit. Each visit includes 5 consecutive orbits, and a phase constraint has been placed on the first exposure of orbit 1 such that orbit 3 is centered on the planetary transit. As the transit duration is fairly short (1 hr), our timing requirement for the first exposure is somewhat strict (30 min) but still allows for some scheduling flexibility. The first orbit for each visit includes ACQ and ACQ/PEAK exposures, and all orbits include a science exposure and a wavecal exposure. Reduced gyro mode would impact our program by limiting the number of transits that could be feasibly scheduled. Our primary target has a fairly long orbital period, so scheduling is already somewhat challenging. Dr. Shreyas Vissapragada is an expert in observations of exoplanet atmospheric escape. He has detected numerous outflows from gas giant and Neptune-sized exoplanets. Larissa Palethorpe and Shishir Dholakia are experts in planetary detection, and are leading the discovery paper for GJ 12b using data from TESS, CHEOPS, MUSCAT, SPECULOOS, and MINERVA. Daisy Turner is an expert in radial velocity analysis and is leading an effort with HARPS-N to measure the mass of GJ 12b. Dr. Annelies Mortier, Dr. Ken Rice, and Dr. Thomas Wilson are experts in the characterization of small exoplanets especially using the radial velocity technique, and are supervising the discovery paper for GJ 12b as well as HARPS-N efforts to measure the planet's mass. Dr. George Zhou is an expert in the characterization of transiting exoplanets using methods like Doppler tomography and Lyman-alpha transit spectroscopy. Exoplanets and Exoplanet Formation 6 false true false false false false SUPPORTED STAR M V-IV Positional data from Gaia DR3, V magnitude from SIMBAD. GJ12 TOI6251 J2000 J2000 STIS/FUV-MAMA Spectroscopic No No G140M 1222 /private/var/folders/jl/jpsf_f1502j0b9g89tkhxxyc0000gn/T/OPVisit7769826299076440182.xml The scheduling data was generated by CASM 33.1. CASM was run in Phase II mode. First transit of GJ 12b. 1756174905000 233.25081079896853 (Tic-Visit :proposal-id 17600 :visit-id "01" :proposal-version -1 :trans-version "20250624" :date "19-Nov-2025 14:50:25.0" :trans-errors '(:WARNINGS 4 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 5 :saa-model "24" :si-bright-earth-limb-angle 20.0 :data-volume 783248 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 17600 :visit-id "01" :obset-id "01" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 17600 :visit-id "01" :orbit-number 1 :pcs-time 380 :si-vis-utilization 2591 :al-overhead-at-end 0 :internal-dur-at-end 360 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 2974 :pcs-gap 0 ) (Tic-Orbit :proposal-id 17600 :visit-id "01" :orbit-number 2 :pcs-time 380 :si-vis-utilization 2630 :al-overhead-at-end 0 :internal-dur-at-end 360 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 2974 :pcs-gap 0 ) (Tic-Orbit :proposal-id 17600 :visit-id "01" :orbit-number 3 :pcs-time 380 :si-vis-utilization 2630 :al-overhead-at-end 0 :internal-dur-at-end 360 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 2974 :pcs-gap 0 ) (Tic-Orbit :proposal-id 17600 :visit-id "01" :orbit-number 4 :pcs-time 380 :si-vis-utilization 2630 :al-overhead-at-end 0 :internal-dur-at-end 360 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 2974 :pcs-gap 0 ) (Tic-Orbit :proposal-id 17600 :visit-id "01" :orbit-number 5 :pcs-time 380 :si-vis-utilization 2630 :al-overhead-at-end 0 :internal-dur-at-end 622 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 2974 :pcs-gap 0 ) true 5 4 /Users/shrey/Desktop/Proposals/HST/HST APT Files/OP-cache/17600-v02.xml The scheduling data was generated by CASM 33.1. CASM was run in Phase II mode. Second transit of GJ 12b. (Tic-Visit :proposal-id 17600 :visit-id "02" :proposal-version -1 :trans-version "20250624" :date "19-Nov-2025 14:49:59.0" :trans-errors '(:WARNINGS 4 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 5 :saa-model "24" :si-bright-earth-limb-angle 20.0 :data-volume 783248 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 17600 :visit-id "02" :obset-id "02" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 17600 :visit-id "02" :orbit-number 1 :pcs-time 380 :si-vis-utilization 2591 :al-overhead-at-end 0 :internal-dur-at-end 360 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 2974 :pcs-gap 0 ) (Tic-Orbit :proposal-id 17600 :visit-id "02" :orbit-number 2 :pcs-time 380 :si-vis-utilization 2630 :al-overhead-at-end 0 :internal-dur-at-end 360 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 2974 :pcs-gap 0 ) (Tic-Orbit :proposal-id 17600 :visit-id "02" :orbit-number 3 :pcs-time 380 :si-vis-utilization 2630 :al-overhead-at-end 0 :internal-dur-at-end 360 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 2974 :pcs-gap 0 ) (Tic-Orbit :proposal-id 17600 :visit-id "02" :orbit-number 4 :pcs-time 380 :si-vis-utilization 2630 :al-overhead-at-end 0 :internal-dur-at-end 360 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 2974 :pcs-gap 0 ) (Tic-Orbit :proposal-id 17600 :visit-id "02" :orbit-number 5 :pcs-time 380 :si-vis-utilization 2630 :al-overhead-at-end 0 :internal-dur-at-end 622 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 2974 :pcs-gap 0 ) true 5 4 The scheduling data was generated by CASM 33.1. CASM was run in Phase II mode. /Users/shrey/Desktop/Proposals/HST/HST APT Files/OP-cache/17600-v03.xml Third transit of GJ 12b (repeat of visit 1 due to MCE reset). (Tic-Visit :proposal-id 17600 :visit-id "03" :proposal-version -1 :trans-version "20250624" :date "19-Nov-2025 14:49:09.0" :trans-errors '(:WARNINGS 4 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 5 :saa-model "24" :si-bright-earth-limb-angle 20.0 :data-volume 783248 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 17600 :visit-id "03" :obset-id "03" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 17600 :visit-id "03" :orbit-number 1 :pcs-time 380 :si-vis-utilization 2591 :al-overhead-at-end 0 :internal-dur-at-end 360 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 2974 :pcs-gap 0 ) (Tic-Orbit :proposal-id 17600 :visit-id "03" :orbit-number 2 :pcs-time 380 :si-vis-utilization 2630 :al-overhead-at-end 0 :internal-dur-at-end 360 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 2974 :pcs-gap 0 ) (Tic-Orbit :proposal-id 17600 :visit-id "03" :orbit-number 3 :pcs-time 380 :si-vis-utilization 2630 :al-overhead-at-end 0 :internal-dur-at-end 360 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 2974 :pcs-gap 0 ) (Tic-Orbit :proposal-id 17600 :visit-id "03" :orbit-number 4 :pcs-time 380 :si-vis-utilization 2630 :al-overhead-at-end 0 :internal-dur-at-end 360 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 2974 :pcs-gap 0 ) (Tic-Orbit :proposal-id 17600 :visit-id "03" :orbit-number 5 :pcs-time 380 :si-vis-utilization 2630 :al-overhead-at-end 0 :internal-dur-at-end 622 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 2974 :pcs-gap 0 ) true 5 4