18236( 2) - 11-May-2026 18:14:34 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 18236 Version: 2 Check-in Time: 11-May-2026 18:14:34 STScI Edit Number: 0 Title Rocky Worlds DDT: HST Observations of HD 260655 ------------------------------------------------------------------------------------ Type Cycle GO 33 ------------------------------------------------------------------------------------ Investigators Contact? PI: Dr. Hannah Diamond-Lowe Space Telescope Science Institute Y CoI: Dr. Nestor Espinoza Space Telescope Science Institute N CoI: Dr. John Henry Debes Space Telescope Science Institute - ESA - N JWST CoI: Dr. Leonardo Dos Santos Space Telescope Science Institute N CoI: Dr. Munazza Alam Space Telescope Science Institute N CoI: Rachel Cooper Space Telescope Science Institute N CoI: Tyler Baines Space Telescope Science Institute N CoI: Taylor James Bell Space Telescope Science Institute - ESA - N JWST CoI: Dr. Brett M. Morris Space Telescope Science Institute N CoI: Dr. Leonardo Ubeda Space Telescope Science Institute N CoI: Dr. Ian Wong Space Telescope Science Institute N CoI: Dr. Joshua D. Lothringer Space Telescope Science Institute N CoI: Ms. Misty Cracraft Space Telescope Science Institute N CoI: Dr. Joseph Filippazzo Space Telescope Science Institute N CoI: Mr. Douglas Ray Long Space Telescope Science Institute N CoI: Dr. Achrene Dyrek Space Telescope Science Institute - ESA - N JWST CoI: Dr. Elena Manjavacas Space Telescope Science Institute - ESA - N JWST CoI: Mees Fix Space Telescope Science Institute N CoI: Dr. Christopher Britt Space Telescope Science Institute N CoI: Hannah Braun Space Telescope Science Institute N CoI: Ryan Kunzer Space Telescope Science Institute N CoI: Kyle Conroy Space Telescope Science Institute N CoI: Dr. Mercedes Lopez-Morales Space Telescope Science Institute N CoI: Dr. I. Neill Reid Space Telescope Science Institute N ------------------------------------------------------------------------------------ Abstract Rocky Worlds is a joint JWST and HST Director's Discretionary Program designed to implement the top recommendations from the Working Group on Strategic Exoplanet Initiatives with HST and JWST. The HST side of the Rocky Worlds DDT focuses on ultraviolet (UV) characterization of the nearby M-dwarf hosts of the rocky planets observed with JWST. We will use COS and STIS to measure the UV to blue-optical spectra of these stars, including UV flare monitoring and measuring the wings of the Ly-alpha profile where appropriate. With these observations we will constrain the high-energy output of these host M dwarfs in the UV, which can be applied to planetary models of atmospheric escape, as well as photochemistry if a planetary atmosphere is present. Complementary observations and analysis to fill in the rest of the M-dwarf panchromatic spectra, from the X-ray to the infrared, are encouraged. 18236( 2) - 11-May-2026 18:14:34 - [ 2] Each M-dwarf planet host observed by HST in the Rocky Worlds DDT program has its own Program ID. The observations in this program will focus on HD 260655 ------------------------------------------------------------------------------------ Observations Description ------------------------ HST observations of HD 260655. 12 orbits of flare monitoring using G130M/1222. 4 orbits of FUV line coverage with G160M/1533 which provides complete coverage with G130M/1222 of 1070-1710 Angstroms. We obtain NUV/Vis low resolution spectroscopy with STIS G230L, and G750L and the 52x0.2 slit in order to construct an accurate stellar SED in one orbit. All UV observations are obtained in time-tag mode to allow for light curves to be generated in the case of a flare or serendipitous transit. For all observation SNR calculations we used archival spectroscopy of HD 260655 from GO 17503 (PI: Diamond-Lowe), with a radius and distance scaled SED for GJ676a from the MUSCLES HLSPs (hlsp_muscles_multi_multi_gj676a_broadband_v25_var-res-sed.fits) for wavelengths beyond 5800 Angstroms, and lines strengths for G160M were estimated from a radius and distance scaled spectrum of GJ676a further scaled by 20% to match the line strengths of species in the archival HD 260655 G130M bandpass. ------------------------------------------------------------------------------------ 18236( 2) - 11-May-2026 18:14:34 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 HD-260655 STAR, EXTRA-SOLAR RA=06H37M9.9436S +/- 0.01", J2000 V = V = 9.593 G=8.88 PLANETARY SYSTEM, M DEC=+17D33'58.74" +/- 0.01" -58.6 V-IV Reference Frame: ICRS Extended: NO Comments: Gaia RV Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 2016.0 -0.053453566029673556 0.337883 0.1000232 ------------------------------------------------------------------------------------------------------------------------------------ 18236( 2) - 11-May-2026 18:14:34 - [ 4] Visit: 01 (G130M-Flare1) Visit Requirements: SCHED 100% On Hold Comments: Additional Comments: Flare Monitoring 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-260655 COS/NUV ACQ/IMA BOA MIRRORA 1 175 S (175 GE S) Comments: Replicated acquisition strategy from GO 17503 ------------------------------------------------------------------------------------------------------------------------------------ 2 HD-260655 COS/FUV TIME-TA PSA G130M 1222 FP-POS=1, BUFFER-TIME=1350 1 1619 S G (1619 S) ------------------------------------------------------------------------------------------------------------------------------------ 3 HD-260655 COS/FUV TIME-TA PSA G130M 1222 FP-POS=2, BUFFER-TIME=1350 1 2426 S G (2426 S) ------------------------------------------------------------------------------------------------------------------------------------ 4 HD-260655 COS/FUV TIME-TA PSA G130M 1222 FP-POS=3, BUFFER-TIME=1350 1 2426 S G (2426 S) ------------------------------------------------------------------------------------------------------------------------------------ 5 HD-260655 COS/FUV TIME-TA PSA G130M 1222 FP-POS=4, BUFFER-TIME=1350 1 2426 S G (2426 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-260655 1 COS/NUV ACQ/IMA BOA MIRRORA none none none none 1 N/A GE HD-260655 2 COS/FUV TIME-TA PSA G130M 1222 none none none none 1 N/A G HD-260655 3 COS/FUV TIME-TA PSA G130M 1222 none none none none 2 N/A G HD-260655 4 COS/FUV TIME-TA PSA G130M 1222 none none none none 3 N/A G HD-260655 5 COS/FUV TIME-TA PSA G130M 1222 none none none none 4 N/A G 18236( 2) - 11-May-2026 18:14:34 - [ 5] Visit: 02 (G130M-Flare2) Visit Requirements: SCHED 100% On Hold Comments: Additional Comments: Flare Monitoring 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-260655 COS/NUV ACQ/IMA BOA MIRRORA 1 175 S (175 GE S) Comments: Replicated acquisition strategy from GO 17503 ------------------------------------------------------------------------------------------------------------------------------------ 2 HD-260655 COS/FUV TIME-TA PSA G130M 1222 FP-POS=1, BUFFER-TIME=1350 1 1619 S G (1619 S) ------------------------------------------------------------------------------------------------------------------------------------ 3 HD-260655 COS/FUV TIME-TA PSA G130M 1222 FP-POS=2, BUFFER-TIME=1350 1 2426 S G (2426 S) ------------------------------------------------------------------------------------------------------------------------------------ 4 HD-260655 COS/FUV TIME-TA PSA G130M 1222 FP-POS=3, BUFFER-TIME=1350 1 2426 S G (2426 S) ------------------------------------------------------------------------------------------------------------------------------------ 5 HD-260655 COS/FUV TIME-TA PSA G130M 1222 FP-POS=4, BUFFER-TIME=1350 1 2426 S G (2426 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-260655 1 COS/NUV ACQ/IMA BOA MIRRORA none none none none 1 N/A GE HD-260655 2 COS/FUV TIME-TA PSA G130M 1222 none none none none 1 N/A G HD-260655 3 COS/FUV TIME-TA PSA G130M 1222 none none none none 2 N/A G HD-260655 4 COS/FUV TIME-TA PSA G130M 1222 none none none none 3 N/A G HD-260655 5 COS/FUV TIME-TA PSA G130M 1222 none none none none 4 N/A G 18236( 2) - 11-May-2026 18:14:34 - [ 6] Visit: 03 (G130M-Flare2) Visit Requirements: SCHED 100% On Hold Comments: Additional Comments: Flare Monitoring 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-260655 COS/NUV ACQ/IMA BOA MIRRORA 1 175 S (175 GE S) Comments: Replicated acquisition strategy from GO 17503 ------------------------------------------------------------------------------------------------------------------------------------ 2 HD-260655 COS/FUV TIME-TA PSA G130M 1222 FP-POS=1, BUFFER-TIME=1350 1 1619 S G (1619 S) ------------------------------------------------------------------------------------------------------------------------------------ 3 HD-260655 COS/FUV TIME-TA PSA G130M 1222 FP-POS=2, BUFFER-TIME=1350 1 2426 S G (2426 S) ------------------------------------------------------------------------------------------------------------------------------------ 4 HD-260655 COS/FUV TIME-TA PSA G130M 1222 FP-POS=3, BUFFER-TIME=1350 1 2426 S G (2426 S) ------------------------------------------------------------------------------------------------------------------------------------ 5 HD-260655 COS/FUV TIME-TA PSA G130M 1222 FP-POS=4, BUFFER-TIME=1350 1 2426 S G (2426 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-260655 1 COS/NUV ACQ/IMA BOA MIRRORA none none none none 1 N/A GE HD-260655 2 COS/FUV TIME-TA PSA G130M 1222 none none none none 1 N/A G HD-260655 3 COS/FUV TIME-TA PSA G130M 1222 none none none none 2 N/A G HD-260655 4 COS/FUV TIME-TA PSA G130M 1222 none none none none 3 N/A G HD-260655 5 COS/FUV TIME-TA PSA G130M 1222 none none none none 4 N/A G 18236( 2) - 11-May-2026 18:14:34 - [ 7] Visit: 04 (G160M-Coverage1) Visit Requirements: SCHED 100% On Hold Comments: Additional Comments: FUV coverage for emission lines, primarily CIV Using CENWAVE 1600 to avoid Si IV, which would be to bright in a flaring condition. This line is well detected in archival data. 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-260655 COS/NUV ACQ/IMA BOA MIRRORA 1 175 S (175 GE S) Comments: Lifetime check for G160M: Initial look is ~4 counts total in the Brightest emission line per FP-POS. We should be ok. ------------------------------------------------------------------------------------------------------------------------------------ 2 HD-260655 COS/FUV TIME-TA PSA G160M 1600 FP-POS=1, BUFFER-TIME=1350 1 1772 S G (1772 S) ------------------------------------------------------------------------------------------------------------------------------------ 3 HD-260655 COS/FUV TIME-TA PSA G160M 1600 FP-POS=2, BUFFER-TIME=1350 1 2422 S G (2422 S) ------------------------------------------------------------------------------------------------------------------------------------ 4 HD-260655 COS/FUV TIME-TA PSA G160M 1600 FP-POS=3, BUFFER-TIME=1350 1 2422 S G (2422 S) ------------------------------------------------------------------------------------------------------------------------------------ 5 HD-260655 COS/FUV TIME-TA PSA G160M 1600 FP-POS=4, BUFFER-TIME=1350 1 2422 S G (2422 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-260655 1 COS/NUV ACQ/IMA BOA MIRRORA none none none none 1 N/A GE HD-260655 2 COS/FUV TIME-TA PSA G160M 1600 none none none none 1 N/A G HD-260655 3 COS/FUV TIME-TA PSA G160M 1600 none none none none 2 N/A G HD-260655 4 COS/FUV TIME-TA PSA G160M 1600 none none none none 3 N/A G HD-260655 5 COS/FUV TIME-TA PSA G160M 1600 none none none none 4 N/A G 18236( 2) - 11-May-2026 18:14:34 - [ 8] Visit: 05 (STIS-Coverage1) Visit Requirements: SCHED 100% On Hold Comments: Additional Comments: UV/Vis characterization 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-260655 STIS/CCD ACQ F28X50OII MIRROR 1 2 S (2 S) I ------------------------------------------------------------------------------------------------------------------------------------ 2 WAVE STIS/NUV ACCUM 52X0.2 G230L 2376 1 DEF (0 S) -MAMA ------------------------------------------------------------------------------------------------------------------------------------ 3 HD-260655 STIS/NUV TIME-TA 52X0.2 G230L 2376 BUFFER-TIME=310 1 637 S (637 -MAMA G S) ------------------------------------------------------------------------------------------------------------------------------------ 4 HD-260655 STIS/NUV TIME-TA 52X0.2 G230L 2376 BUFFER-TIME=310 1 637 S (637 -MAMA G S) ------------------------------------------------------------------------------------------------------------------------------------ 5 HD-260655 STIS/CCD ACCUM 52X0.2 G750L 7751 CR-SPLIT=2, WAVECAL=NO 1 20 S (20 S) ------------------------------------------------------------------------------------------------------------------------------------ 6 WAVE STIS/CCD ACCUM 52X0.2 G750L 7751 1 DEF (0 S) ------------------------------------------------------------------------------------------------------------------------------------ 7 CCDFLAT STIS/CCD ACCUM 0.3X0.09 G750L 7751 2 DEF (0 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-260655 1 STIS/CCD ACQ F28X50OI MIRROR none none none none 1 N/A II WAVE 2 STIS/NUV ACCUM 52X0.2 G230L 2376 none none none none 1 N/A -MAMA HD-260655 3 STIS/NUV TIME-TA 52X0.2 G230L 2376 none none none none 1 N/A -MAMA G HD-260655 4 STIS/NUV TIME-TA 52X0.2 G230L 2376 none none none none 1 N/A -MAMA G HD-260655 5 STIS/CCD ACCUM 52X0.2 G750L 7751 none none none 1 1 N/A HD-260655 5 STIS/CCD ACCUM 52X0.2 G750L 7751 none none none 2 1 N/A WAVE 6 STIS/CCD ACCUM 52X0.2 G750L 7751 none none none none 1 N/A CCDFLAT 7 STIS/CCD ACCUM 0.3X0.09 G750L 7751 none none 1 none 1 N/A CCDFLAT 7 STIS/CCD ACCUM 0.3X0.09 G750L 7751 none none 2 none 1 N/A 18236( 2) - 11-May-2026 18:14:34 - [ 9] Summary Form for Proposal 18236 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures 0.3X0.09, 52X0.2, BOA, F28X50OIII, PSA ------------------------------------------------------------------------------------------------------------------------------------ Configurations COS/FUV, COS/NUV, STIS/CCD, STIS/NUV-MAMA ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM, ACQ, ACQ/IMAGE, TIME-TAG ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters BUFFER-TIME=1350, BUFFER-TIME=310, CR-SPLIT=2, FP-POS=1, FP-POS=2, FP-POS=3, FP-POS=4, WAVECAL=NO ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements SCHED 100% ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements G130M, G160M, G230L, G750L, MIRROR, MIRRORA ------------------------------------------------------------------------------------------------------------------------------------ Target Names CCDFLAT, HD-260655, WAVE ------------------------------------------------------------------------------------------------------------------------------------