18086( 8) - 13-Feb-2026 20:00:46 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 18086 Version: 8 Check-in Time: 13-Feb-2026 20:00:46 STScI Edit Number: 0 Title The impact of stellar feedback as revealed by thousands of resolved HII regions in NGC 253 ------------------------------------------------------------------------------------ Type Cycle GO 33 ------------------------------------------------------------------------------------ Investigators Contact? PI: Rebecca McClain The Ohio State University Y CoI: Dr. Adam Leroy The Ohio State University N CoI: Dr. David Thilker The Johns Hopkins University N CoI: Dr. Ashley Barnes European Southern Observatory - Germany N CoI: Dr. Rupali Chandar University of Toledo N CoI: Dr. Thomas Williams University of Manchester N CoI: Mr. Ivan Sergeevich Gerasimov University Cote d'Azur N CoI: Elias K Oakes University of Connecticut N CoI: Qiushi Chris Tian Universiteit Leiden N CoI: Prof. Laura Lopez The Ohio State University N CoI: Prof. Alberto Bolatto University of Maryland N ------------------------------------------------------------------------------------ Abstract We propose for full-disk narrowband H-alpha imaging of NGC253, the nearest southern massive, star-forming spiral galaxy. This imaging is critical to resolve the inner structure of 2, 500 HII regions known from full-disk VLT/MUSE spectral mapping and JWST/MIRI imaging. The proposed mapping would also complement awarded HST broadband imaging that captures the stellar populations powering these regions. HII regions are the critical locations of pre-supernova stellar feedback. However, even at the 3.5 Mpc distance to NGC253, ground-based observations cannot resolve the size or morphology of the inner cores where this feedback plays out. Only HST can reach the required ~1 pc resolution. Combining these new HST data with the VLT/MUSE, JWST, and broadband HST mapping, we will (1) measure the size and morphology of each region, (2) relate these to the mass, location, and age of the powering stellar population, and (3) compare the distribution of ionized gas to the observed PAH and dust emission from JWST, linking the feedback to the surrounding ISM and testing models of PAH destruction in ionized gas. This proposal will be the first-ever data set that combines full optical spectral mapping, JWST IR imaging, pc-resolution ionized gas mapping, and resolved UV-optical mapping of the stellar population. This unprecedented data set is crucial for expanding our understanding of HII region physics and stellar feedback, along with the countless possible applications to resolved sources, ISM, stellar, and galactic wind studies. ------------------------------------------------------------------------------------ Observations Description ------------------------ We have designed a full-disk survey of NGC 253 to observe the F657N band of WFC3/UVIS. This wavelength probes the H-alpha emission across the galaxy, tracing areas of active star formation on the smallest scales of individual HII regions. In combination with the full-galaxy MUSE and JWST imaging, HST H-alpha imaging will reveal the inner structure and chemical composition of HII regions, providing crucial information on the impacts of stellar feedback. 18086( 8) - 13-Feb-2026 20:00:46 - [ 2] This program has been designed to match the orientation and coverage of the previously awarded observations of NUV-visbile filters (GO 17809). The mosaic is organized in a 2x8 tile layout with 10% overlap. We require the orientation angle to be 272.0-272.4 deg in order to match the in progress HST observations and existing JWST/MIRI imaging. The matching mosaic layout is crucial for continuum subtraction in the proposed bands. Each exposure will be 430 seconds, allowing us to detect HII regions powered by single massive stars within the disk. We will reach S/N of 10 for luminosities 10^35 erg/s. ------------------------------------------------------------------------------------ 18086( 8) - 13-Feb-2026 20:00:46 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 5 NGC-253-V13 GALAXY, SPIRAL ARM RA=00H47M50.9061S, J2000 V = 7 DEC=-25D15'56.09" Reference Frame: ICRS Comments: This object was generated by the targetselector and retrieved from the SIMBAD database. Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 2000 0.0 0.0 0.0 ------------------------------------------------------------------------------------------------------------------------------------ 6 NGC-253-V14 GALAXY, SPIRAL ARM RA=00H47M41.9790S, J2000 V = 7 DEC=-25D17'34.07" Reference Frame: ICRS Comments: This object was generated by the targetselector and retrieved from the SIMBAD database. Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 2000 0.0 0.0 0.0 ------------------------------------------------------------------------------------------------------------------------------------ 7 NGC-253-V15 GALAXY, SPIRAL ARM RA=00H47M33.0520S, J2000 V = 7 DEC=-25D19'12.01" Reference Frame: ICRS Comments: This object was generated by the targetselector and retrieved from the SIMBAD database. Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 2000 0.0 0.0 0.0 ------------------------------------------------------------------------------------------------------------------------------------ 8 NGC-253-V16 GALAXY, SPIRAL ARM RA=00H47M24.1249S, J2000 V = 7 DEC=-25D20'49.93" Reference Frame: ICRS Comments: This object was generated by the targetselector and retrieved from the SIMBAD database. Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 2000 0.0 0.0 0.0 ------------------------------------------------------------------------------------------------------------------------------------ 9 NGC-253-V17 GALAXY, SPIRAL ARM RA=00H47M43.0018S, J2000 V = 7 DEC=-25D14'22.11" Reference Frame: ICRS Comments: This object was generated by the targetselector and retrieved from the SIMBAD database. Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 2000 0.0 0.0 0.0 ------------------------------------------------------------------------------------------------------------------------------------ 18086( 8) - 13-Feb-2026 20:00:46 - [ 4] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 10 NGC-253-V18 GALAXY, SPIRAL ARM RA=00H47M34.0747S, J2000 V = 7 DEC=-25D15'39.00" Reference Frame: ICRS Comments: This object was generated by the targetselector and retrieved from the SIMBAD database. Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 2000 0.0 0.0 0.0 ------------------------------------------------------------------------------------------------------------------------------------ 11 NGC-253-V19 GALAXY, SPIRAL ARM RA=00H47M25.1476S, J2000 V = 7 DEC=-25D17'16.91" Reference Frame: ICRS Comments: This object was generated by the targetselector and retrieved from the SIMBAD database. Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 2000 0.0 0.0 0.0 ------------------------------------------------------------------------------------------------------------------------------------ 12 NGC-253-V20 GALAXY, SPIRAL ARM RA=00H47M16.2205S, J2000 V = 7 DEC=-25D18'54.80" Reference Frame: ICRS Comments: This object was generated by the targetselector and retrieved from the SIMBAD database. Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 2000 0.0 0.0 0.0 ------------------------------------------------------------------------------------------------------------------------------------ 13 NGC-253-END1 GALAXY, SPIRAL ARM RA=00H47M3.0626S, J2000 V = 7 DEC=-25D23'4.81" Reference Frame: ICRS Comments: This object was generated by the targetselector and retrieved from the SIMBAD database. Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 2000 0.0 0.0 0.0 ------------------------------------------------------------------------------------------------------------------------------------ 14 NGC-253-END1 GALAXY, SPIRAL ARM RA=00H47M11.5868S, J2000 V = 7 2 DEC=-25D21'30.47" Reference Frame: ICRS Comments: This object was generated by the targetselector and retrieved from the SIMBAD database. Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 2000 0.0 0.0 0.0 ------------------------------------------------------------------------------------------------------------------------------------ 18086( 8) - 13-Feb-2026 20:00:46 - [ 5] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 15 NGC-253-END2 GALAXY, SPIRAL ARM RA=00H48M5.0016S, J2000 V = 7 DEC=-25D11'49.82" Reference Frame: ICRS Comments: This object was generated by the targetselector and retrieved from the SIMBAD database. Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 2000 0.0 0.0 0.0 ------------------------------------------------------------------------------------------------------------------------------------ 16 NGC-253-END2 GALAXY, SPIRAL ARM RA=00H47M56.2515S, J2000 V = 7 2 DEC=-25D13'25.43" Reference Frame: ICRS Comments: This object was generated by the targetselector and retrieved from the SIMBAD database. Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 2000 0.0 0.0 0.0 ------------------------------------------------------------------------------------------------------------------------------------ 18086( 8) - 13-Feb-2026 20:00:46 - [ 6] Patterns ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 1 Primary_Pattern Secondary_Pattern Pattern_Type WFC3-UVIS-DITHER-LINE-3PT Pattern_Purpose DITHER Number_Of_Points 4 Point_Spacing 0.135 Line_Spacing Coordinate_Frame POS-TARG Pattern_Orient 46.84 Angle_Between_Sides Center_Pattern NO ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 2 Primary_Pattern Secondary_Pattern Pattern_Type WFC3-UVIS-DITHER-LINE Pattern_Purpose DITHER Number_Of_Points 2 Point_Spacing 0.145 Line_Spacing Coordinate_Frame POS-TARG Pattern_Orient 46.84 Angle_Between_Sides Center_Pattern NO ------------------------------------------------------------------------------------------------------------------------------------ 18086( 8) - 13-Feb-2026 20:00:46 - [ 7] Visit: 01 Visit Requirements: ORIENT 272D TO 272.4 D 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 NGC-253-END WFC3/UVI ACCUM UVIS-FIX F657N FLASH=20 1 544 S POS TARG null, -19.81; 1 S (1088 S) PATTERN 2 1 ------------------------------------------------------------------------------------------------------------------------------------ 2 NGC-253-END WFC3/UVI ACCUM UVIS-FIX F657N FLASH=20 1 544 S POS TARG null, 19.81; 1 S (1088 S) PATTERN 2 2 ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ NGC-253-END1 1 WFC3/UVI ACCUM UVIS-FIX F657N 1 none none none 1 N/A S NGC-253-END1 1 WFC3/UVI ACCUM UVIS-FIX F657N 2 none none none 1 N/A S NGC-253-END1 2 WFC3/UVI ACCUM UVIS-FIX F657N 1 none none none 1 N/A S NGC-253-END1 2 WFC3/UVI ACCUM UVIS-FIX F657N 2 none none none 1 N/A S 18086( 8) - 13-Feb-2026 20:00:46 - [ 8] Visit: 02 Visit Requirements: ORIENT 272D TO 272.4 D 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 NGC-253-END WFC3/UVI ACCUM UVIS-FIX F657N FLASH=20 1 544 S POS TARG null, -29; 12 S (1088 S) PATTERN 2 1 ------------------------------------------------------------------------------------------------------------------------------------ 2 NGC-253-END WFC3/UVI ACCUM UVIS-FIX F657N FLASH=20 1 544 S POS TARG null, 29; 12 S (1088 S) PATTERN 2 2 ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ NGC-253-END12 1 WFC3/UVI ACCUM UVIS-FIX F657N 1 none none none 1 N/A S NGC-253-END12 1 WFC3/UVI ACCUM UVIS-FIX F657N 2 none none none 1 N/A S NGC-253-END12 2 WFC3/UVI ACCUM UVIS-FIX F657N 1 none none none 1 N/A S NGC-253-END12 2 WFC3/UVI ACCUM UVIS-FIX F657N 2 none none none 1 N/A S 18086( 8) - 13-Feb-2026 20:00:46 - [ 9] Visit: 03 Visit Requirements: ORIENT 272D TO 272.4 D 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 NGC-253-END WFC3/UVI ACCUM UVIS-FIX F657N FLASH=20 1 544 S POS TARG null, -19.81; 2 S (1088 S) PATTERN 2 1 ------------------------------------------------------------------------------------------------------------------------------------ 2 NGC-253-END WFC3/UVI ACCUM UVIS-FIX F657N FLASH=20 1 544 S POS TARG null, 19.81; 2 S (1088 S) PATTERN 2 2 ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ NGC-253-END2 1 WFC3/UVI ACCUM UVIS-FIX F657N 1 none none none 1 N/A S NGC-253-END2 1 WFC3/UVI ACCUM UVIS-FIX F657N 2 none none none 1 N/A S NGC-253-END2 2 WFC3/UVI ACCUM UVIS-FIX F657N 1 none none none 1 N/A S NGC-253-END2 2 WFC3/UVI ACCUM UVIS-FIX F657N 2 none none none 1 N/A S 18086( 8) - 13-Feb-2026 20:00:46 - [ 10] Visit: 04 Visit Requirements: ORIENT 272D TO 272.4 D 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 NGC-253-END WFC3/UVI ACCUM UVIS-FIX F657N FLASH=20 1 544 S POS TARG null, -29; 22 S (1088 S) PATTERN 2 1 ------------------------------------------------------------------------------------------------------------------------------------ 2 NGC-253-END WFC3/UVI ACCUM UVIS-FIX F657N FLASH=20 1 544 S POS TARG null, 29; 22 S (1088 S) PATTERN 2 2 ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ NGC-253-END22 1 WFC3/UVI ACCUM UVIS-FIX F657N 1 none none none 1 N/A S NGC-253-END22 1 WFC3/UVI ACCUM UVIS-FIX F657N 2 none none none 1 N/A S NGC-253-END22 2 WFC3/UVI ACCUM UVIS-FIX F657N 1 none none none 1 N/A S NGC-253-END22 2 WFC3/UVI ACCUM UVIS-FIX F657N 2 none none none 1 N/A S 18086( 8) - 13-Feb-2026 20:00:46 - [ 11] Visit: 05 Visit Requirements: ORIENT 272D TO 272.4 D 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 NGC-253-V13 WFC3/UVI ACCUM UVIS-FIX F657N FLASH=20 1 544 S PATTERN 1 1 S (2176 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 | ------------------------------------------------------------------------------------------------------------------------------------ NGC-253-V13 1 WFC3/UVI ACCUM UVIS-FIX F657N 1 none none none 1 N/A S NGC-253-V13 1 WFC3/UVI ACCUM UVIS-FIX F657N 2 none none none 1 N/A S NGC-253-V13 1 WFC3/UVI ACCUM UVIS-FIX F657N 3 none none none 1 N/A S NGC-253-V13 1 WFC3/UVI ACCUM UVIS-FIX F657N 4 none none none 1 N/A S 18086( 8) - 13-Feb-2026 20:00:46 - [ 12] Visit: 06 Visit Requirements: ORIENT 272D TO 272.4 D 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 NGC-253-V14 WFC3/UVI ACCUM UVIS-FIX F657N FLASH=20 1 544 S PATTERN 1 1 S (2176 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 | ------------------------------------------------------------------------------------------------------------------------------------ NGC-253-V14 1 WFC3/UVI ACCUM UVIS-FIX F657N 1 none none none 1 N/A S NGC-253-V14 1 WFC3/UVI ACCUM UVIS-FIX F657N 2 none none none 1 N/A S NGC-253-V14 1 WFC3/UVI ACCUM UVIS-FIX F657N 3 none none none 1 N/A S NGC-253-V14 1 WFC3/UVI ACCUM UVIS-FIX F657N 4 none none none 1 N/A S 18086( 8) - 13-Feb-2026 20:00:46 - [ 13] Visit: 07 Visit Requirements: ORIENT 272D TO 272.4 D 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 NGC-253-V15 WFC3/UVI ACCUM UVIS-FIX F657N FLASH=20 1 544 S PATTERN 1 1 S (2176 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 | ------------------------------------------------------------------------------------------------------------------------------------ NGC-253-V15 1 WFC3/UVI ACCUM UVIS-FIX F657N 1 none none none 1 N/A S NGC-253-V15 1 WFC3/UVI ACCUM UVIS-FIX F657N 2 none none none 1 N/A S NGC-253-V15 1 WFC3/UVI ACCUM UVIS-FIX F657N 3 none none none 1 N/A S NGC-253-V15 1 WFC3/UVI ACCUM UVIS-FIX F657N 4 none none none 1 N/A S 18086( 8) - 13-Feb-2026 20:00:46 - [ 14] Visit: 08 Visit Requirements: ORIENT 272D TO 272.4 D 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 NGC-253-V16 WFC3/UVI ACCUM UVIS-FIX F657N FLASH=20 1 544 S PATTERN 1 1 S (2176 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 | ------------------------------------------------------------------------------------------------------------------------------------ NGC-253-V16 1 WFC3/UVI ACCUM UVIS-FIX F657N 1 none none none 1 N/A S NGC-253-V16 1 WFC3/UVI ACCUM UVIS-FIX F657N 2 none none none 1 N/A S NGC-253-V16 1 WFC3/UVI ACCUM UVIS-FIX F657N 3 none none none 1 N/A S NGC-253-V16 1 WFC3/UVI ACCUM UVIS-FIX F657N 4 none none none 1 N/A S 18086( 8) - 13-Feb-2026 20:00:46 - [ 15] Visit: 09 Visit Requirements: ORIENT 341D TO 349 D 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 NGC-253-V17 WFC3/UVI ACCUM UVIS-FIX F657N FLASH=20 1 544 S PATTERN 1 1 S (2176 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 | ------------------------------------------------------------------------------------------------------------------------------------ NGC-253-V17 1 WFC3/UVI ACCUM UVIS-FIX F657N 1 none none none 1 N/A S NGC-253-V17 1 WFC3/UVI ACCUM UVIS-FIX F657N 2 none none none 1 N/A S NGC-253-V17 1 WFC3/UVI ACCUM UVIS-FIX F657N 3 none none none 1 N/A S NGC-253-V17 1 WFC3/UVI ACCUM UVIS-FIX F657N 4 none none none 1 N/A S 18086( 8) - 13-Feb-2026 20:00:46 - [ 16] Visit: 10 Visit Requirements: ORIENT 272D TO 272.4 D 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 NGC-253-V18 WFC3/UVI ACCUM UVIS-FIX F657N FLASH=20 1 544 S PATTERN 1 1 S (2176 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 | ------------------------------------------------------------------------------------------------------------------------------------ NGC-253-V18 1 WFC3/UVI ACCUM UVIS-FIX F657N 1 none none none 1 N/A S NGC-253-V18 1 WFC3/UVI ACCUM UVIS-FIX F657N 2 none none none 1 N/A S NGC-253-V18 1 WFC3/UVI ACCUM UVIS-FIX F657N 3 none none none 1 N/A S NGC-253-V18 1 WFC3/UVI ACCUM UVIS-FIX F657N 4 none none none 1 N/A S 18086( 8) - 13-Feb-2026 20:00:46 - [ 17] Visit: 11 Visit Requirements: ORIENT 272D TO 272.4 D 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 NGC-253-V19 WFC3/UVI ACCUM UVIS-FIX F657N FLASH=20 1 544 S PATTERN 1 1 S (2176 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 | ------------------------------------------------------------------------------------------------------------------------------------ NGC-253-V19 1 WFC3/UVI ACCUM UVIS-FIX F657N 1 none none none 1 N/A S NGC-253-V19 1 WFC3/UVI ACCUM UVIS-FIX F657N 2 none none none 1 N/A S NGC-253-V19 1 WFC3/UVI ACCUM UVIS-FIX F657N 3 none none none 1 N/A S NGC-253-V19 1 WFC3/UVI ACCUM UVIS-FIX F657N 4 none none none 1 N/A S 18086( 8) - 13-Feb-2026 20:00:46 - [ 18] Visit: 12 Visit Requirements: ORIENT 272D TO 272.4 D 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 NGC-253-V20 WFC3/UVI ACCUM UVIS-FIX F657N FLASH=20 1 544 S PATTERN 1 1 S (2176 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 | ------------------------------------------------------------------------------------------------------------------------------------ NGC-253-V20 1 WFC3/UVI ACCUM UVIS-FIX F657N 1 none none none 1 N/A S NGC-253-V20 1 WFC3/UVI ACCUM UVIS-FIX F657N 2 none none none 1 N/A S NGC-253-V20 1 WFC3/UVI ACCUM UVIS-FIX F657N 3 none none none 1 N/A S NGC-253-V20 1 WFC3/UVI ACCUM UVIS-FIX F657N 4 none none none 1 N/A S 18086( 8) - 13-Feb-2026 20:00:46 - [ 19] Summary Form for Proposal 18086 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures UVIS-FIX ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFC3/UVIS ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters FLASH=20 ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements ORIENT 272D TO 272.4 D, ORIENT 341D TO 349 D, PATTERN 1 1, PATTERN 2 1, PATTERN 2 2, POS TARG null, -19.81, POS TARG null, -29, POS TARG null, 19.81, POS TARG null, 29 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F657N ------------------------------------------------------------------------------------------------------------------------------------ Target Names NGC-253-END1, NGC-253-END12, NGC-253-END2, NGC-253-END22, NGC-253-V13, NGC-253-V14, NGC-253-V15, NGC-253-V16, NGC-253-V17, NGC-253-V18, NGC-253-V19, NGC-253-V20 ------------------------------------------------------------------------------------------------------------------------------------