17903( 2) - 16-Jan-2026 15:46:29 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 17903 Version: 2 Check-in Time: 16-Jan-2026 15:46:29 STScI Edit Number: 0 Title Rocky Worlds DDT: HST Observations of LTT 1445A ------------------------------------------------------------------------------------ Type Cycle GO/DD 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: Rachel Plesha 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: Hannah Braun Space Telescope Science Institute N CoI: Kelly Lepo 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. 17903( 2) - 16-Jan-2026 15:46:29 - [ 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 LT 1445A, obtaining flare monitoring in G130M/1222 and adding STIS coverage of G230L and G750L to augment archival data of the star in GO 16701 and GO 16722 that include COS/G130M, STIS/G140M, COS/G160M, STIS/G230L, COS/G230L, and STIS/G430L. NOTE: LTT 1445B was 5.09" to the west and 5.10" to the East in 2016 (Gaia DR3) just outside the 7" bright object radius, consisting of magnetically active M dwarfs of later type. These companions are not safe if they fall in the STIS long slit, and thus an ORIENT constraint is placed on the STIS Visit 4. In 2022 using WFC3/IR imaging, the closest star was separated by 7.06", implying that by 2026 it will still be ~7" away. ------------------------------------------------------------------------------------ Observations Description ------------------------ HST observations of LTT 1445A. 12 orbits of flare monitoring using G130M/1222. 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 and leverage the Mg II 2800 emission lines to tie to archival observations. 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 observations we used the LTT 1445A MUSCLES SED with constant resolution, and a custom HSLA combination of archival spectra for SNR calculations in the above modes. These observations mimic characterization of other M dwarfs from previous programs. LTT1445BC was checked in case it flared during NUV STIS G230L since the 52x0.2 slit could intersect the BC component. It was determined to be unsafe so ORIENT constraints are present, following https://hst-docs.stsci.edu/stisihb/chapter-11-data-taking/11-4-fixing-orientati on-on-the-sky, I calculated a +/-20 degree avoidance window assuming a PA of ------------------------------------------------------------------------------------ 17903( 2) - 16-Jan-2026 15:46:29 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 BD-17-588A EXT-STAR, EMISSION LINE RA=03H01M50.9819S +/- 0.01", J2000 V = V = 11.22 STAR, EXTRA-SOLAR DEC=-16D35'40.32" +/- 0.01" -5.74 PLANETARY SYSTEM, M V-IV Reference Frame: ICRS Extended: NO Comments: Gaia Coordinates used 11/6/2025 Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 2016 -0.02573673963211554 -0.2679309999848556 0.14569220000000002 ------------------------------------------------------------------------------------------------------------------------------------ 17903( 2) - 16-Jan-2026 15:46:29 - [ 4] Visit: 01 (Flare Monitoring A) Visit Requirements: SCHED 100% On Hold Comments: Additional Comments: Flare monitoring of LTT 1445A 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 BD-17-588A COS/NUV ACQ/IMA PSA MIRRORB 1 46 S (46 GE S) Comments: Copied from 16722. Flaring clearance available in CS report for 16722 ------------------------------------------------------------------------------------------------------------------------------------ 2 BD-17-588A COS/FUV TIME-TA PSA G130M 1222 FP-POS=1, BUFFER-TIME=939 1 1878 S G (1878 S) ------------------------------------------------------------------------------------------------------------------------------------ 3 BD-17-588A COS/FUV TIME-TA PSA G130M 1222 FP-POS=2, BUFFER-TIME=1213 1 2426 S G (2426 S) ------------------------------------------------------------------------------------------------------------------------------------ 4 BD-17-588A COS/FUV TIME-TA PSA G130M 1222 FP-POS=3, BUFFER-TIME=1213 1 2426 S G (2426 S) ------------------------------------------------------------------------------------------------------------------------------------ 5 BD-17-588A COS/FUV TIME-TA PSA G130M 1222 FP-POS=4, BUFFER-TIME=1213 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 | ------------------------------------------------------------------------------------------------------------------------------------ BD-17-588A 1 COS/NUV ACQ/IMA PSA MIRRORB none none none none 1 N/A GE BD-17-588A 2 COS/FUV TIME-TA PSA G130M 1222 none none none none 1 N/A G BD-17-588A 3 COS/FUV TIME-TA PSA G130M 1222 none none none none 2 N/A G BD-17-588A 4 COS/FUV TIME-TA PSA G130M 1222 none none none none 3 N/A G BD-17-588A 5 COS/FUV TIME-TA PSA G130M 1222 none none none none 4 N/A G 17903( 2) - 16-Jan-2026 15:46:29 - [ 5] Visit: 02 (Flare Monitoring B) Visit Requirements: SCHED 100% On Hold Comments: Additional Comments: Flare monitoring of LTT 1445A 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 BD-17-588A COS/NUV ACQ/IMA PSA MIRRORB 1 46 S (46 GE S) Comments: Copied from 16722. Flaring clearance available in CS report for 16722 ------------------------------------------------------------------------------------------------------------------------------------ 2 BD-17-588A COS/FUV TIME-TA PSA G130M 1222 FP-POS=1, BUFFER-TIME=939 1 1878 S G (1878 S) ------------------------------------------------------------------------------------------------------------------------------------ 3 BD-17-588A COS/FUV TIME-TA PSA G130M 1222 FP-POS=2, BUFFER-TIME=1213 1 2426 S G (2426 S) ------------------------------------------------------------------------------------------------------------------------------------ 4 BD-17-588A COS/FUV TIME-TA PSA G130M 1222 FP-POS=3, BUFFER-TIME=1213 1 2426 S G (2426 S) ------------------------------------------------------------------------------------------------------------------------------------ 5 BD-17-588A COS/FUV TIME-TA PSA G130M 1222 FP-POS=4, BUFFER-TIME=1213 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 | ------------------------------------------------------------------------------------------------------------------------------------ BD-17-588A 1 COS/NUV ACQ/IMA PSA MIRRORB none none none none 1 N/A GE BD-17-588A 2 COS/FUV TIME-TA PSA G130M 1222 none none none none 1 N/A G BD-17-588A 3 COS/FUV TIME-TA PSA G130M 1222 none none none none 2 N/A G BD-17-588A 4 COS/FUV TIME-TA PSA G130M 1222 none none none none 3 N/A G BD-17-588A 5 COS/FUV TIME-TA PSA G130M 1222 none none none none 4 N/A G 17903( 2) - 16-Jan-2026 15:46:29 - [ 6] Visit: 03 (Flare Monitoring C) Visit Requirements: SCHED 100% On Hold Comments: Additional Comments: Flare monitoring of LTT 1445A 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 BD-17-588A COS/NUV ACQ/IMA PSA MIRRORB 1 46 S (46 GE S) Comments: Copied from 16722. Flaring clearance available in CS report for 16722 ------------------------------------------------------------------------------------------------------------------------------------ 2 BD-17-588A COS/FUV TIME-TA PSA G130M 1222 FP-POS=1, BUFFER-TIME=939 1 1878 S G (1878 S) ------------------------------------------------------------------------------------------------------------------------------------ 3 BD-17-588A COS/FUV TIME-TA PSA G130M 1222 FP-POS=2, BUFFER-TIME=1213 1 2426 S G (2426 S) ------------------------------------------------------------------------------------------------------------------------------------ 4 BD-17-588A COS/FUV TIME-TA PSA G130M 1222 FP-POS=3, BUFFER-TIME=1213 1 2426 S G (2426 S) ------------------------------------------------------------------------------------------------------------------------------------ 5 BD-17-588A COS/FUV TIME-TA PSA G130M 1222 FP-POS=4, BUFFER-TIME=1213 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 | ------------------------------------------------------------------------------------------------------------------------------------ BD-17-588A 1 COS/NUV ACQ/IMA PSA MIRRORB none none none none 1 N/A GE BD-17-588A 2 COS/FUV TIME-TA PSA G130M 1222 none none none none 1 N/A G BD-17-588A 3 COS/FUV TIME-TA PSA G130M 1222 none none none none 2 N/A G BD-17-588A 4 COS/FUV TIME-TA PSA G130M 1222 none none none none 3 N/A G BD-17-588A 5 COS/FUV TIME-TA PSA G130M 1222 none none none none 4 N/A G 17903( 2) - 16-Jan-2026 15:46:29 - [ 7] Visit: 04 (STIS-Coverage1) Visit Requirements: SCHED 80%; ORIENT 22D TO 162 D; ORIENT 202D TO 342 D 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 BD-17-588A STIS/CCD ACQ F28X50OII MIRROR 1 5 S (5 S) I ------------------------------------------------------------------------------------------------------------------------------------ 2 WAVE STIS/NUV ACCUM 52X0.2 G230L 2376 1 DEF (0 S) -MAMA ------------------------------------------------------------------------------------------------------------------------------------ 3 BD-17-588A STIS/NUV TIME-TA 52X0.2 G230L 2376 BUFFER-TIME=300, WAVECAL=NO 1 1530 S -MAMA G (1530 S) ------------------------------------------------------------------------------------------------------------------------------------ 4 BD-17-588A STIS/CCD ACCUM 52X0.2 G750L 7751 CR-SPLIT=2 1 5 S (5 S) ------------------------------------------------------------------------------------------------------------------------------------ 5 WAVE STIS/CCD ACCUM 52X0.2 G750L 7751 1 DEF (0 S) ------------------------------------------------------------------------------------------------------------------------------------ 6 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 | ------------------------------------------------------------------------------------------------------------------------------------ BD-17-588A 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 BD-17-588A 3 STIS/NUV TIME-TA 52X0.2 G230L 2376 none none none none 1 N/A -MAMA G BD-17-588A 4 STIS/CCD ACCUM 52X0.2 G750L 7751 none none none 1 1 N/A BD-17-588A 4 STIS/CCD ACCUM 52X0.2 G750L 7751 none none none 2 1 N/A WAVE 5 STIS/CCD ACCUM 52X0.2 G750L 7751 none none none none 1 N/A CCDFLAT 6 STIS/CCD ACCUM 0.3X0.09 G750L 7751 none none 1 none 1 N/A CCDFLAT 6 STIS/CCD ACCUM 0.3X0.09 G750L 7751 none none 2 none 1 N/A 17903( 2) - 16-Jan-2026 15:46:29 - [ 8] Summary Form for Proposal 17903 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures 0.3X0.09, 52X0.2, F28X50OIII, PSA ------------------------------------------------------------------------------------------------------------------------------------ Configurations COS/FUV, COS/NUV, STIS/CCD, STIS/NUV-MAMA ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM, ACQ, ACQ/IMAGE, TIME-TAG ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters BUFFER-TIME=1213, BUFFER-TIME=300, BUFFER-TIME=939, CR-SPLIT=2, FP-POS=1, FP-POS=2, FP-POS=3, FP-POS=4, WAVECAL=NO ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements ORIENT 202D TO 342 D, ORIENT 22D TO 162 D, SCHED 100%, SCHED 80% ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements G130M, G230L, G750L, MIRROR, MIRRORB ------------------------------------------------------------------------------------------------------------------------------------ Target Names BD-17-588A, CCDFLAT, WAVE ------------------------------------------------------------------------------------------------------------------------------------