18027( 4) - 19-Nov-2025 19:03:27 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 18027 Version: 4 Check-in Time: 19-Nov-2025 19:03:27 STScI Edit Number: 1 Title Securing the HST Surface Brightness Fluctuation Legacy with a Robust JWST Calibration ------------------------------------------------------------------------------------ Type Cycle GO 33 ------------------------------------------------------------------------------------ Investigators Contact? PI: Dr. Joseph Jensen Utah Valley University Y CoI: Dr. R. Brent Tully University of Hawaii N CoI: Dr. John P. Blakeslee NOIRLab - (AZ) N CoI: Dr. Michele Cantiello INAF - Osservatorio Astronomico d'Abruzzo N CoI: Dr. Ehsan Kourkchi University of Hawaii N CoI: Dr. Gagandeep Singh Anand Space Telescope Science Institute N ------------------------------------------------------------------------------------ Abstract Addressing the "Hubble tension" is a top priority for JWST, and several programs have been awarded time to construct a completely independent distance ladder based on old populations in elliptical galaxies instead of Cepheid variable stars in spiral galaxies. In particular, tip of the red giant branch (TRGB) stars have been measured in 14 early-type galaxies with JWST for the purpose of calibrating the surface brightness fluctuation (SBF) method. However, thus far only 8 of these galaxies have SBF measurements with HST WFC3/IR. We propose to complete the calibration linkage between HST and JWST by using HST WFC3/IR to observe the remaining 6 galaxies with established JWST TRGB distances. The result will be a higher precision zero point for the HST SBF sample, expanding the calibration from 8 to 14 galaxies. The TRGB calibration of SBF decouples the large archival sample of over 230 HST IR SBF measurements from the Cepheid-SN Ia ladder. The HST SBF sample, spanning the sky and extending to 100 Mpc, provides an independent estimate of the Hubble constant based solely on old stellar populations. ------------------------------------------------------------------------------------ Observations Description ------------------------ Imaging observations of six elliptical galaxies closer than 20 Mpc in WFC3/IR basic imaging mode, using the default dither pattern with N=4 steps to correct for bad pixels. One orbit per galaxy. Two filters will be used (F110W and F160W) with observations split into four dither positions in each filter. The readout mode of SPARS50 and NSAMP=6 provides 1012 sec in each filter. ------------------------------------------------------------------------------------ 18027( 4) - 19-Nov-2025 19:03:27 - [ 2] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 NGC-1549 GALAXY, ELLIPTICAL RA=04H15M45.1056S, J2000 V = 1243 V = 9.8 J=9.1 DEC=-55D35'31.85" Reference Frame: Other: NED Extended: YES Comments: This object was generated by the targetselector and retrieved from the NED database. ------------------------------------------------------------------------------------------------------------------------------------ 2 MESSIER-084 GALAXY, ELLIPTICAL RA=12H25M3.7440S, J2000 V = 1017 V = 9.07 DEC=+12D53'13.13" Reference Frame: Other: NED Extended: YES Comments: This object was generated by the targetselector and retrieved from the NED database. ------------------------------------------------------------------------------------------------------------------------------------ 3 MESSIER-086 GALAXY, ELLIPTICAL RA=12H26M11.7432S, J2000 V = -224 V = 8.84 DEC=+12D56'46.39" Reference Frame: Other: NED Extended: YES Comments: This object was generated by the targetselector and retrieved from the NED database. ------------------------------------------------------------------------------------------------------------------------------------ 4 MESSIER-059 GALAXY, ELLIPTICAL RA=12H42M2.2440S, J2000 V = 467 V = 9.61 DEC=+11D38'49.31" Reference Frame: Other: NED Extended: YES Comments: This object was generated by the targetselector and retrieved from the NED database. ------------------------------------------------------------------------------------------------------------------------------------ 5 MESSIER-087 GALAXY, ELLIPTICAL RA=12H30M49.4232S, J2000 V = 1284 V = 8.56 DEC=+12D23'28.03" Reference Frame: Other: NED Comments: This object was generated by the targetselector and retrieved from the NED database. ------------------------------------------------------------------------------------------------------------------------------------ 6 MESSIER-105 GALAXY, ELLIPTICAL RA=10H47M49.5888S, J2000 V = 907 V = 9.28 DEC=+12D34'53.83" Reference Frame: Other: NED Extended: YES Comments: This object was generated by the targetselector and retrieved from the NED database. ------------------------------------------------------------------------------------------------------------------------------------ 18027( 4) - 19-Nov-2025 19:03:27 - [ 3] Patterns ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 1 Primary_Pattern Secondary_Pattern Pattern_Type WFC3-IR-DITHER-BLOB Pattern_Purpose DITHER Number_Of_Points 4 Point_Spacing 5.183 Line_Spacing Coordinate_Frame POS-TARG Pattern_Orient 41.859 Angle_Between_Sides Center_Pattern YES ------------------------------------------------------------------------------------------------------------------------------------ 18027( 4) - 19-Nov-2025 19:03:27 - [ 4] Visit: 01 (NGC-1549) Visit Requirements: SCHED 90% 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-1549 WFC3/IR MULTIAC IR F110W SAMP-SEQ=STEP50, NSAMP=10 1 DEF GS ACQ SCENARIO ONEB1OR; CUM (996.928 PATTERN 1 1 S) ------------------------------------------------------------------------------------------------------------------------------------ 2 NGC-1549 WFC3/IR MULTIAC IR F160W SAMP-SEQ=STEP50, NSAMP=10 1 DEF PATTERN 1 2 CUM (996.928 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-1549 1 WFC3/IR MULTIAC IR F110W 1 none none none 1 N/A CUM NGC-1549 1 WFC3/IR MULTIAC IR F110W 2 none none none 1 N/A CUM NGC-1549 1 WFC3/IR MULTIAC IR F110W 3 none none none 1 N/A CUM NGC-1549 1 WFC3/IR MULTIAC IR F110W 4 none none none 1 N/A CUM NGC-1549 2 WFC3/IR MULTIAC IR F160W 1 none none none 1 N/A CUM NGC-1549 2 WFC3/IR MULTIAC IR F160W 2 none none none 1 N/A CUM NGC-1549 2 WFC3/IR MULTIAC IR F160W 3 none none none 1 N/A CUM NGC-1549 2 WFC3/IR MULTIAC IR F160W 4 none none none 1 N/A CUM 18027( 4) - 19-Nov-2025 19:03:27 - [ 5] Visit: 02 (MESSIER-084) Visit Requirements: SCHED 80% 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 MESSIER-084 WFC3/IR MULTIAC IR F110W SAMP-SEQ=STEP50, NSAMP=10 1 DEF GS ACQ SCENARIO ONEB1OR; CUM (996.928 PATTERN 1 1 S) ------------------------------------------------------------------------------------------------------------------------------------ 2 MESSIER-084 WFC3/IR MULTIAC IR F160W SAMP-SEQ=STEP50, NSAMP=10 1 DEF PATTERN 1 2 CUM (996.928 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 | ------------------------------------------------------------------------------------------------------------------------------------ MESSIER-084 1 WFC3/IR MULTIAC IR F110W 1 none none none 1 N/A CUM MESSIER-084 1 WFC3/IR MULTIAC IR F110W 2 none none none 1 N/A CUM MESSIER-084 1 WFC3/IR MULTIAC IR F110W 3 none none none 1 N/A CUM MESSIER-084 1 WFC3/IR MULTIAC IR F110W 4 none none none 1 N/A CUM MESSIER-084 2 WFC3/IR MULTIAC IR F160W 1 none none none 1 N/A CUM MESSIER-084 2 WFC3/IR MULTIAC IR F160W 2 none none none 1 N/A CUM MESSIER-084 2 WFC3/IR MULTIAC IR F160W 3 none none none 1 N/A CUM MESSIER-084 2 WFC3/IR MULTIAC IR F160W 4 none none none 1 N/A CUM 18027( 4) - 19-Nov-2025 19:03:27 - [ 6] Visit: 03 (MESSIER-086) Visit Requirements: SCHED 80% 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 MESSIER-086 WFC3/IR MULTIAC IR F110W SAMP-SEQ=STEP50, NSAMP=10 1 DEF GS ACQ SCENARIO ONEB1OR; CUM (996.928 PATTERN 1 1 S) ------------------------------------------------------------------------------------------------------------------------------------ 2 MESSIER-086 WFC3/IR MULTIAC IR F160W SAMP-SEQ=STEP50, NSAMP=10 1 DEF PATTERN 1 2 CUM (996.928 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 | ------------------------------------------------------------------------------------------------------------------------------------ MESSIER-086 1 WFC3/IR MULTIAC IR F110W 1 none none none 1 N/A CUM MESSIER-086 1 WFC3/IR MULTIAC IR F110W 2 none none none 1 N/A CUM MESSIER-086 1 WFC3/IR MULTIAC IR F110W 3 none none none 1 N/A CUM MESSIER-086 1 WFC3/IR MULTIAC IR F110W 4 none none none 1 N/A CUM MESSIER-086 2 WFC3/IR MULTIAC IR F160W 1 none none none 1 N/A CUM MESSIER-086 2 WFC3/IR MULTIAC IR F160W 2 none none none 1 N/A CUM MESSIER-086 2 WFC3/IR MULTIAC IR F160W 3 none none none 1 N/A CUM MESSIER-086 2 WFC3/IR MULTIAC IR F160W 4 none none none 1 N/A CUM 18027( 4) - 19-Nov-2025 19:03:27 - [ 7] Visit: 04 (MESSIER-059) Visit Requirements: SCHED 80% 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 MESSIER-059 WFC3/IR MULTIAC IR F110W SAMP-SEQ=STEP50, NSAMP=10 1 DEF GS ACQ SCENARIO ONEB1OR; CUM (996.928 PATTERN 1 1 S) ------------------------------------------------------------------------------------------------------------------------------------ 2 MESSIER-059 WFC3/IR MULTIAC IR F160W SAMP-SEQ=STEP50, NSAMP=10 1 DEF PATTERN 1 2 CUM (996.928 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 | ------------------------------------------------------------------------------------------------------------------------------------ MESSIER-059 1 WFC3/IR MULTIAC IR F110W 1 none none none 1 N/A CUM MESSIER-059 1 WFC3/IR MULTIAC IR F110W 2 none none none 1 N/A CUM MESSIER-059 1 WFC3/IR MULTIAC IR F110W 3 none none none 1 N/A CUM MESSIER-059 1 WFC3/IR MULTIAC IR F110W 4 none none none 1 N/A CUM MESSIER-059 2 WFC3/IR MULTIAC IR F160W 1 none none none 1 N/A CUM MESSIER-059 2 WFC3/IR MULTIAC IR F160W 2 none none none 1 N/A CUM MESSIER-059 2 WFC3/IR MULTIAC IR F160W 3 none none none 1 N/A CUM MESSIER-059 2 WFC3/IR MULTIAC IR F160W 4 none none none 1 N/A CUM 18027( 4) - 19-Nov-2025 19:03:27 - [ 8] Visit: 05 (MESSIER-087) Visit Requirements: SCHED 80% 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 MESSIER-087 WFC3/IR MULTIAC IR F110W SAMP-SEQ=STEP50, NSAMP=10 1 DEF GS ACQ SCENARIO ONEB1OR; CUM (996.928 PATTERN 1 1 S) ------------------------------------------------------------------------------------------------------------------------------------ 2 MESSIER-087 WFC3/IR MULTIAC IR F160W SAMP-SEQ=STEP50, NSAMP=10 1 DEF PATTERN 1 2 CUM (996.928 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 | ------------------------------------------------------------------------------------------------------------------------------------ MESSIER-087 1 WFC3/IR MULTIAC IR F110W 1 none none none 1 N/A CUM MESSIER-087 1 WFC3/IR MULTIAC IR F110W 2 none none none 1 N/A CUM MESSIER-087 1 WFC3/IR MULTIAC IR F110W 3 none none none 1 N/A CUM MESSIER-087 1 WFC3/IR MULTIAC IR F110W 4 none none none 1 N/A CUM MESSIER-087 2 WFC3/IR MULTIAC IR F160W 1 none none none 1 N/A CUM MESSIER-087 2 WFC3/IR MULTIAC IR F160W 2 none none none 1 N/A CUM MESSIER-087 2 WFC3/IR MULTIAC IR F160W 3 none none none 1 N/A CUM MESSIER-087 2 WFC3/IR MULTIAC IR F160W 4 none none none 1 N/A CUM 18027( 4) - 19-Nov-2025 19:03:27 - [ 9] Visit: 06 (MESSIER-105) Visit Requirements: SCHED 80% 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 MESSIER-105 WFC3/IR MULTIAC IR F110W SAMP-SEQ=STEP50, NSAMP=10 1 DEF GS ACQ SCENARIO ONEB1OR; CUM (996.928 PATTERN 1 1 S) ------------------------------------------------------------------------------------------------------------------------------------ 2 MESSIER-105 WFC3/IR MULTIAC IR F160W SAMP-SEQ=STEP50, NSAMP=10 1 DEF PATTERN 1 2 CUM (996.928 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 | ------------------------------------------------------------------------------------------------------------------------------------ MESSIER-105 1 WFC3/IR MULTIAC IR F110W 1 none none none 1 N/A CUM MESSIER-105 1 WFC3/IR MULTIAC IR F110W 2 none none none 1 N/A CUM MESSIER-105 1 WFC3/IR MULTIAC IR F110W 3 none none none 1 N/A CUM MESSIER-105 1 WFC3/IR MULTIAC IR F110W 4 none none none 1 N/A CUM MESSIER-105 2 WFC3/IR MULTIAC IR F160W 1 none none none 1 N/A CUM MESSIER-105 2 WFC3/IR MULTIAC IR F160W 2 none none none 1 N/A CUM MESSIER-105 2 WFC3/IR MULTIAC IR F160W 3 none none none 1 N/A CUM MESSIER-105 2 WFC3/IR MULTIAC IR F160W 4 none none none 1 N/A CUM 18027( 4) - 19-Nov-2025 19:03:27 - [ 10] Summary Form for Proposal 18027 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures IR ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFC3/IR ------------------------------------------------------------------------------------------------------------------------------------ Opmodes MULTIACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters NSAMP=10, SAMP-SEQ=STEP50 ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements GS ACQ SCENARIO ONEB1OR, PATTERN 1 1, PATTERN 1 2, SCHED 80%, SCHED 90% ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F110W, F160W ------------------------------------------------------------------------------------------------------------------------------------ Target Names MESSIER-059, MESSIER-084, MESSIER-086, MESSIER-087, MESSIER-105, NGC-1549 ------------------------------------------------------------------------------------------------------------------------------------