18121( 10) - 19-Feb-2026 18:55:20 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 18121 Version: 10 Check-in Time: 19-Feb-2026 18:55:20 STScI Edit Number: 6 Title A Punctured Pufferfish: Atmospheric Escape from a Neptune-mass Planet Inflated to the Size of Jupiter ------------------------------------------------------------------------------------ Type Cycle GO 33 ------------------------------------------------------------------------------------ Investigators Contact? PI: Dr. Girish M. Duvvuri Vanderbilt University Y CoI: Prof. Kevin France University of Colorado at Boulder N CoI: Dr. Christian Schneider Christian-Albrechts Universitat zu Kiel N CoI: Dr. Alexander Brown University of Colorado at Boulder N CoI: Dr. Antonio Garcia Munoz Universite Paris-Saclay N CoI: Prof. Adina Feinstein Michigan State University N CoI: Dr. Andrew Withycombe Mann University of North Carolina at Chapel N Hill CoI: Dr. Allison Youngblood NASA Goddard Space Flight Center N CoI: Daniel Peter Thorngren The Johns Hopkins University N CoI: Dr. Elisabeth R. Newton Dartmouth College N CoI: Dr. Keighley Elizabeth Rockcliffe University of Maryland Baltimore County N CoI: Dr. David John Wilson University of Colorado at Boulder N CoI: Pa Chia Thao University of North Carolina at Chapel N Hill CoI: Dr. Yamila Miguel Universiteit Leiden N CoI: Dr. John Sebastian Pineda University of Colorado at Boulder N CoI: Dr. Cynthia Suzanne Froning Southwest Research Institute N CoI: Dr. Zach K. Berta-Thompson University of Colorado at Boulder N CoI: Dr. Catriona Anne Murray University of Colorado at Boulder N CoI: Dr. Peter Gao Carnegie Institution of Washington N CoI: Prof. Keivan G. Stassun Vanderbilt University N ------------------------------------------------------------------------------------ Abstract We propose to observe 5 transits of HIP 67522 b, a Neptune-mass planet inflated to Jupiter's size orbiting a 17 Myr old solar analog, in the near ultraviolet to measure its mass loss rate, outflow velocity, and exospheric structure. HIP 67522 b is a planet where we can precisely measure transit depths with both Hubble and JWST and study a planet's atmosphere as a structure in its entirety instead of piecemeal. In fact, JWST has already measured this planet's infrared transmission spectrum. The goal is to use the metallicity constraint from JWST in tandem with HST near-ultraviolet transits to measure the rate of Fe+ and Mg+ mass-loss for HIP 67522 b, construct the most complete map of a young planet's escaping atmosphere thus far, and thereby anchor the initial stages of sub-Jovian-mass planet evolution. ------------------------------------------------------------------------------------ Observations Description ------------------------ We will observe five transits of HIP 67522 b using the STIS/G230L instrument/grating centered at 2376 Angstroms. This near ultraviolet wavelength range will span transitions of Fe I, Fe II, and Mg II, enabling us to search for atsmopheric escape in these metal lines. We will observe the five transits 18121( 10) - 19-Feb-2026 18:55:20 - [ 2] with five visits of five orbits each, spaced out in phase to encompass a potentially extended ingress/egress and to account for the 20 minute transit timing variation amplitude induced by the outer planet HIP 67522 c. Each visit will start with a target acquisition exposure using the F28X50OII filter for 1 second, a setting which was previously successful for this target. The remainder of the first orbit and the entirety of the next four orbits in each visit will filled with an exposure of STIS/G230L centered at 2376 Angstroms with a buffer time of 350s (as done for the previous out-of-transit G230L observation). The phase windows for the first exposure of each orbit are 0.011 phase units wide (6614 seconds / 1.837 hours), and defined such that the individual visit windows are spaced apart in phase relative to mid-transit as follows: 0.956 -- 0.967, 0.967 -- 0.978, 0.978 -- 0.989, 0.989 -- 1.0, and 0 -- 0.011. This means that the very first exposure of the earliest visit will be slightly greater than 1.5 transit durations before mid-transit, while the end of the last exposure will be slightly less than 2 transit durations after mid-transit. ------------------------------------------------------------------------------------ 18121( 10) - 19-Feb-2026 18:55:20 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 HD-120411 STAR, G V-IV RA=13H50M6.2797S, J2000 V = 9.8 DEC=-40D50'8.88" Reference Frame: ICRS Comments: This object was generated by the targetselector and retrieved from the SIMBAD database. SIMBAD listed proper motion for this target. When retrieving targets with PM from SIMBAD, APT requests the coordinates be calculated with an epoch of the year 2000. Do not modify this epoch. Always review coordinates using the Target Confirmation tool, which graphically displays the PM. Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 2000 -0.0025471416630195444 -0.02224800005024008 0.008017 ------------------------------------------------------------------------------------------------------------------------------------ 18121( 10) - 19-Feb-2026 18:55:20 - [ 4] Visit: 01 Visit Requirements: Period 6.9594731 D AND ZERO-PHASE HJD2458604.02376 On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exp | Target | Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Num | Name | Config | Mode | or FOV |Element |Waveln.| Parameters |Exp| (Total) | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 HD-120411 STIS/CCD ACQ F28X50OII MIRROR 1 1 S (1 S) PHASE 0.956 TO 0.967 ------------------------------------------------------------------------------------------------------------------------------------ 2 HD-120411 STIS/NUV TIME-TA 52X2 G230L 2376 BUFFER-TIME=200 1 1739 S PHASE 0.956 TO 0.967 -MAMA G (1739 S) ------------------------------------------------------------------------------------------------------------------------------------ 3 HD-120411 STIS/NUV TIME-TA 52X2 G230L 2376 BUFFER-TIME=200 1 2568 S -MAMA G (2568 S) ------------------------------------------------------------------------------------------------------------------------------------ 4 HD-120411 STIS/NUV TIME-TA 52X2 G230L 2376 BUFFER-TIME=200 1 2568 S -MAMA G (2568 S) ------------------------------------------------------------------------------------------------------------------------------------ 5 HD-120411 STIS/NUV TIME-TA 52X2 G230L 2376 BUFFER-TIME=200 1 2568 S -MAMA G (2568 S) ------------------------------------------------------------------------------------------------------------------------------------ 6 HD-120411 STIS/NUV TIME-TA 52X2 G230L 2376 BUFFER-TIME=200 1 2568 S -MAMA G (2568 S) ------------------------------------------------------------------------------------------------------------------------------------ Sub Exposures ------------------------------------------------------------------------------------------------------------------------------------ Target | Exp |Instr | Oper. | Aper |Spectral|Cent.|Primary |Secondary |Iteration |CR-SPLIT |Orbit |Duration Name | Num |Config | Mode | or FOV |Element |Wave.|Pattern Pos |Pattern Pos |Num |Num |Number | ------------------------------------------------------------------------------------------------------------------------------------ HD-120411 1 STIS/CCD ACQ F28X50OI MIRROR none none none none 1 N/A I HD-120411 2 STIS/NUV TIME-TA 52X2 G230L 2376 none none none none 1 N/A -MAMA G HD-120411 3 STIS/NUV TIME-TA 52X2 G230L 2376 none none none none 2 N/A -MAMA G HD-120411 4 STIS/NUV TIME-TA 52X2 G230L 2376 none none none none 3 N/A -MAMA G HD-120411 5 STIS/NUV TIME-TA 52X2 G230L 2376 none none none none 4 N/A -MAMA G HD-120411 6 STIS/NUV TIME-TA 52X2 G230L 2376 none none none none 5 N/A -MAMA G 18121( 10) - 19-Feb-2026 18:55:20 - [ 5] Visit: 02 Visit Requirements: Period 6.9594731 D AND ZERO-PHASE HJD2458604.02376 On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exp | Target | Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Num | Name | Config | Mode | or FOV |Element |Waveln.| Parameters |Exp| (Total) | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 HD-120411 STIS/CCD ACQ F28X50OII MIRROR 1 1 S (1 S) PHASE 0.967 TO 0.978 ------------------------------------------------------------------------------------------------------------------------------------ 2 HD-120411 STIS/NUV TIME-TA 52X2 G230L 2376 BUFFER-TIME=200 1 1719 S PHASE 0.967 TO 0.978 -MAMA G (1719 S) ------------------------------------------------------------------------------------------------------------------------------------ 3 HD-120411 STIS/NUV TIME-TA 52X2 G230L 2376 BUFFER-TIME=200 1 2593 S -MAMA G (2593 S) ------------------------------------------------------------------------------------------------------------------------------------ 4 HD-120411 STIS/NUV TIME-TA 52X2 G230L 2376 BUFFER-TIME=200 1 2568 S -MAMA G (2568 S) ------------------------------------------------------------------------------------------------------------------------------------ 5 HD-120411 STIS/NUV TIME-TA 52X2 G230L 2376 BUFFER-TIME=200 1 2568 S -MAMA G (2568 S) ------------------------------------------------------------------------------------------------------------------------------------ 6 HD-120411 STIS/NUV TIME-TA 52X2 G230L 2376 BUFFER-TIME=200 1 2568 S -MAMA G (2568 S) ------------------------------------------------------------------------------------------------------------------------------------ Sub Exposures ------------------------------------------------------------------------------------------------------------------------------------ Target | Exp |Instr | Oper. | Aper |Spectral|Cent.|Primary |Secondary |Iteration |CR-SPLIT |Orbit |Duration Name | Num |Config | Mode | or FOV |Element |Wave.|Pattern Pos |Pattern Pos |Num |Num |Number | ------------------------------------------------------------------------------------------------------------------------------------ HD-120411 1 STIS/CCD ACQ F28X50OI MIRROR none none none none 1 N/A I HD-120411 2 STIS/NUV TIME-TA 52X2 G230L 2376 none none none none 1 N/A -MAMA G HD-120411 3 STIS/NUV TIME-TA 52X2 G230L 2376 none none none none 2 N/A -MAMA G HD-120411 4 STIS/NUV TIME-TA 52X2 G230L 2376 none none none none 3 N/A -MAMA G HD-120411 5 STIS/NUV TIME-TA 52X2 G230L 2376 none none none none 4 N/A -MAMA G HD-120411 6 STIS/NUV TIME-TA 52X2 G230L 2376 none none none none 5 N/A -MAMA G 18121( 10) - 19-Feb-2026 18:55:20 - [ 6] Visit: 03 Visit Requirements: Period 6.9594731 D AND ZERO-PHASE HJD2458604.02376 On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exp | Target | Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Num | Name | Config | Mode | or FOV |Element |Waveln.| Parameters |Exp| (Total) | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 HD-120411 STIS/CCD ACQ F28X50OII MIRROR 1 1 S (1 S) PHASE 0.978 TO 0.989 ------------------------------------------------------------------------------------------------------------------------------------ 2 HD-120411 STIS/NUV TIME-TA 52X2 G230L 2376 BUFFER-TIME=200 1 1719 S PHASE 0.978 TO 0.989 -MAMA G (1719 S) ------------------------------------------------------------------------------------------------------------------------------------ 3 HD-120411 STIS/NUV TIME-TA 52X2 G230L 2376 BUFFER-TIME=200 1 2593 S -MAMA G (2593 S) ------------------------------------------------------------------------------------------------------------------------------------ 4 HD-120411 STIS/NUV TIME-TA 52X2 G230L 2376 BUFFER-TIME=200 1 2568 S -MAMA G (2568 S) ------------------------------------------------------------------------------------------------------------------------------------ 5 HD-120411 STIS/NUV TIME-TA 52X2 G230L 2376 BUFFER-TIME=200 1 2568 S -MAMA G (2568 S) ------------------------------------------------------------------------------------------------------------------------------------ 6 HD-120411 STIS/NUV TIME-TA 52X2 G230L 2376 BUFFER-TIME=200 1 2568 S -MAMA G (2568 S) ------------------------------------------------------------------------------------------------------------------------------------ Sub Exposures ------------------------------------------------------------------------------------------------------------------------------------ Target | Exp |Instr | Oper. | Aper |Spectral|Cent.|Primary |Secondary |Iteration |CR-SPLIT |Orbit |Duration Name | Num |Config | Mode | or FOV |Element |Wave.|Pattern Pos |Pattern Pos |Num |Num |Number | ------------------------------------------------------------------------------------------------------------------------------------ HD-120411 1 STIS/CCD ACQ F28X50OI MIRROR none none none none 1 N/A I HD-120411 2 STIS/NUV TIME-TA 52X2 G230L 2376 none none none none 1 N/A -MAMA G HD-120411 3 STIS/NUV TIME-TA 52X2 G230L 2376 none none none none 2 N/A -MAMA G HD-120411 4 STIS/NUV TIME-TA 52X2 G230L 2376 none none none none 3 N/A -MAMA G HD-120411 5 STIS/NUV TIME-TA 52X2 G230L 2376 none none none none 4 N/A -MAMA G HD-120411 6 STIS/NUV TIME-TA 52X2 G230L 2376 none none none none 5 N/A -MAMA G 18121( 10) - 19-Feb-2026 18:55:20 - [ 7] Visit: 04 Visit Requirements: Period 6.9594731 D AND ZERO-PHASE HJD2458604.02376 On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exp | Target | Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Num | Name | Config | Mode | or FOV |Element |Waveln.| Parameters |Exp| (Total) | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 HD-120411 STIS/CCD ACQ F28X50OII MIRROR 1 1 S (1 S) PHASE 0.986 TO 1.0 ------------------------------------------------------------------------------------------------------------------------------------ 2 HD-120411 STIS/NUV TIME-TA 52X2 G230L 2376 BUFFER-TIME=200 1 1719 S PHASE 0.986 TO 1.0 -MAMA G (1719 S) ------------------------------------------------------------------------------------------------------------------------------------ 3 HD-120411 STIS/NUV TIME-TA 52X2 G230L 2376 BUFFER-TIME=200 1 2593 S -MAMA G (2593 S) ------------------------------------------------------------------------------------------------------------------------------------ 4 HD-120411 STIS/NUV TIME-TA 52X2 G230L 2376 BUFFER-TIME=200 1 2568 S -MAMA G (2568 S) ------------------------------------------------------------------------------------------------------------------------------------ 5 HD-120411 STIS/NUV TIME-TA 52X2 G230L 2376 BUFFER-TIME=200 1 2568 S -MAMA G (2568 S) ------------------------------------------------------------------------------------------------------------------------------------ 6 HD-120411 STIS/NUV TIME-TA 52X2 G230L 2376 BUFFER-TIME=200 1 2568 S -MAMA G (2568 S) ------------------------------------------------------------------------------------------------------------------------------------ Sub Exposures ------------------------------------------------------------------------------------------------------------------------------------ Target | Exp |Instr | Oper. | Aper |Spectral|Cent.|Primary |Secondary |Iteration |CR-SPLIT |Orbit |Duration Name | Num |Config | Mode | or FOV |Element |Wave.|Pattern Pos |Pattern Pos |Num |Num |Number | ------------------------------------------------------------------------------------------------------------------------------------ HD-120411 1 STIS/CCD ACQ F28X50OI MIRROR none none none none 1 N/A I HD-120411 2 STIS/NUV TIME-TA 52X2 G230L 2376 none none none none 1 N/A -MAMA G HD-120411 3 STIS/NUV TIME-TA 52X2 G230L 2376 none none none none 2 N/A -MAMA G HD-120411 4 STIS/NUV TIME-TA 52X2 G230L 2376 none none none none 3 N/A -MAMA G HD-120411 5 STIS/NUV TIME-TA 52X2 G230L 2376 none none none none 4 N/A -MAMA G HD-120411 6 STIS/NUV TIME-TA 52X2 G230L 2376 none none none none 5 N/A -MAMA G 18121( 10) - 19-Feb-2026 18:55:20 - [ 8] Visit: 05 Visit Requirements: ORIENT 287D TO 293 D; Period 6.9594731 D AND ZERO-PHASE HJD2458604.02376 On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exp | Target | Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Num | Name | Config | Mode | or FOV |Element |Waveln.| Parameters |Exp| (Total) | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 HD-120411 STIS/CCD ACQ F28X50OII MIRROR 1 1 S (1 S) PHASE 0.0 TO 0.011 ------------------------------------------------------------------------------------------------------------------------------------ 2 HD-120411 STIS/NUV TIME-TA 52X2 G230L 2376 BUFFER-TIME=200 1 1719 S PHASE 0.0 TO 0.011 -MAMA G (1719 S) ------------------------------------------------------------------------------------------------------------------------------------ 3 HD-120411 STIS/NUV TIME-TA 52X2 G230L 2376 BUFFER-TIME=200 1 2593 S -MAMA G (2593 S) ------------------------------------------------------------------------------------------------------------------------------------ 4 HD-120411 STIS/NUV TIME-TA 52X2 G230L 2376 BUFFER-TIME=200 1 2568 S -MAMA G (2568 S) ------------------------------------------------------------------------------------------------------------------------------------ 5 HD-120411 STIS/NUV TIME-TA 52X2 G230L 2376 BUFFER-TIME=200 1 2568 S -MAMA G (2568 S) ------------------------------------------------------------------------------------------------------------------------------------ 6 HD-120411 STIS/NUV TIME-TA 52X2 G230L 2376 BUFFER-TIME=200 1 2568 S -MAMA G (2568 S) ------------------------------------------------------------------------------------------------------------------------------------ Sub Exposures ------------------------------------------------------------------------------------------------------------------------------------ Target | Exp |Instr | Oper. | Aper |Spectral|Cent.|Primary |Secondary |Iteration |CR-SPLIT |Orbit |Duration Name | Num |Config | Mode | or FOV |Element |Wave.|Pattern Pos |Pattern Pos |Num |Num |Number | ------------------------------------------------------------------------------------------------------------------------------------ HD-120411 1 STIS/CCD ACQ F28X50OI MIRROR none none none none 1 N/A I HD-120411 2 STIS/NUV TIME-TA 52X2 G230L 2376 none none none none 1 N/A -MAMA G HD-120411 3 STIS/NUV TIME-TA 52X2 G230L 2376 none none none none 2 N/A -MAMA G HD-120411 4 STIS/NUV TIME-TA 52X2 G230L 2376 none none none none 3 N/A -MAMA G HD-120411 5 STIS/NUV TIME-TA 52X2 G230L 2376 none none none none 4 N/A -MAMA G HD-120411 6 STIS/NUV TIME-TA 52X2 G230L 2376 none none none none 5 N/A -MAMA G 18121( 10) - 19-Feb-2026 18:55:20 - [ 9] Summary Form for Proposal 18121 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures 52X2, F28X50OII ------------------------------------------------------------------------------------------------------------------------------------ Configurations STIS/CCD, STIS/NUV-MAMA ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ, TIME-TAG ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters BUFFER-TIME=200 ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements ORIENT 287D TO 293 D, PHASE 0.0 TO 0.011, PHASE 0.956 TO 0.967, PHASE 0.967 TO 0.978, PHASE 0.978 TO 0.989, PHASE 0.986 TO 1.0, Period 6.9594731 D AND ZERO-PHASE HJD2458604.02376 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements G230L, MIRROR ------------------------------------------------------------------------------------------------------------------------------------ Target Names HD-120411 ------------------------------------------------------------------------------------------------------------------------------------