18006( 8) - 16-Jan-2026 17:15:41 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 18006 Version: 8 Check-in Time: 16-Jan-2026 17:15:41 STScI Edit Number: 6 Title Geophysical Characterization of the Distant Ocean World Makemake ------------------------------------------------------------------------------------ Type Cycle GO 33 ------------------------------------------------------------------------------------ Investigators Contact? PI: Dr. Benjamin Proudfoot University of Central Florida Board of Y Trustees CoI: Prof. Darin Ragozzine Brigham Young University N CoI: Dr. Will M. Grundy Lowell Observatory N CoI: Dr. Bryan Jason Holler Space Telescope Science Institute N ------------------------------------------------------------------------------------ Abstract Recent JWST observations have revealed that the trans-Neptunian object (TNO) Makemake has a prominant IR excess indicating the existence of Enceladus-style hotspots on its surface. This makes Makemake possibly one of the Solar System's most distant ocean worlds. Unfortunately, little is known about many of the basic properties of Makemake, making high-fidelity geophysical investigations almost impossible. To solve this, we propose an investigation to measure the mass, density, and pole-axis orientation of Makemake via astrometric tracking of its small satellite, nicknamed MK2. Measuring mass and density will help to constrain the ongoing radiogenic heating of Makemake and provide firm footing for models of Makemake's interior structure. Determining Makemake's pole-axis orientation will provide critical context for interpreting the JWST thermal measurements and could help to constrain the geographical extent of any hotspots. Leveraging over a dozen orbits from past HST programs, we require just 4 well-timed HST orbits to complete our investigation, which will revolutionize our knowledge of Makemake and enable high-fidelity geophysical modeling of this distant ocean world. ------------------------------------------------------------------------------------ Observations Description ------------------------ Our observations call for 4 single-orbit visits to image the Makemake system using the WFC3/UVIS instrument. During each visit, images will be acquired using the UVIS2-C512C-SUB aperture, paired with the F350LP filter to optimize astrometric precision. Exposure times are chosen to optimize SNR and schedulability, with 10+ dithered images taken during each visit. This allows us to remain robust to unlucky cosmic ray hits. Scheduling of observations is important to the goals of our program. The timing windows input into the Phase II are somewhat flexible, and can be changed if needed. If more observing windows are needed, we can provide them, although these are our "optimal" windows. We would prefer if each visit is at least 18 days apart, although this is not strictly necessary. Since poorly oriented diffraction spikes can degrade the astrometric quality of our observations, we request observations avoid orients where the diffraction spikes are aligned with the satellite's orbit. Inputting these a priori is 18006( 8) - 16-Jan-2026 17:15:41 - [ 2] difficult/time-consuming since the position of the satellite and orient ranges change in time. Once preliminary scheduling windows based on "betweens" are identified, we can further input the orients which are allowed. We will also check for bright nearby stars that could degrade image quality. ------------------------------------------------------------------------------------ 18006( 8) - 16-Jan-2026 17:15:41 - [ 3] TARGET LIST Solar System Targets ------------------------------------------------------------------------------------------------------------------------------------ TARGET NUMBER: 1 TARGET NAME: MAKEMAKE ------------------------------------------------------------------------------------------------------------------------------------ TARGET DESCRIPTION: DWARF-PLANET Makemake ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 1 TARGET POSITION LEVEL 2 STD=MAKEMAKE ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 3 WINDOWS ------------------------------------------------------------------------------------------------------------------------------------ DATA COMMENTS V = 17 Ephemeris Center: EARTH ------------------------------------------------------------------------------------------------------------------------------------ 18006( 8) - 16-Jan-2026 17:15:41 - [ 4] Patterns ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 1 Primary_Pattern Secondary_Pattern Pattern_Type WFC3-UVIS-DITHER-BOX Pattern_Purpose DITHER Number_Of_Points 4 Point_Spacing 0.173 Line_Spacing 0.112 Coordinate_Frame POS-TARG Pattern_Orient 23.884 Angle_Between_Sides 81.785 Center_Pattern NO ------------------------------------------------------------------------------------------------------------------------------------ 18006( 8) - 16-Jan-2026 17:15:41 - [ 5] Visit: 01 (Period verify) Visit Requirements: BETWEEN 01-DEC-2025:00:00:00 AND 02-DEC-2025:00:00:00; BETWEEN 07-DEC-2025:16:00:00 AND 11-DEC-2025:00:00:00; BETWEEN 16-DEC-2025:16:00:00 AND 19-DEC-2025:20:00:00; BETWEEN 25-DEC-2025:16:00:00 AND 29-DEC-2025:00:00:00 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 MAKEMAKE WFC3/UVI ACCUM UVIS2-C51 F350LP FLASH=7 1 120 S (480 GS ACQ SCENARIO ONEB1OR; S 2C-SUB S) SEQ 1-3 NON-INT; PATTERN 1 1 ------------------------------------------------------------------------------------------------------------------------------------ 2 MAKEMAKE WFC3/UVI ACCUM UVIS2-C51 F350LP FLASH=7 1 120 S (480 PATTERN 1 2 S 2C-SUB S) ------------------------------------------------------------------------------------------------------------------------------------ 3 MAKEMAKE WFC3/UVI ACCUM UVIS2-C51 F350LP FLASH=7 1 120 S (480 PATTERN 1 3 S 2C-SUB 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 | ------------------------------------------------------------------------------------------------------------------------------------ MAKEMAKE 1 WFC3/UVI ACCUM UVIS2-C5 F350LP 1 none none none 1 N/A S 12C-SUB MAKEMAKE 1 WFC3/UVI ACCUM UVIS2-C5 F350LP 2 none none none 1 N/A S 12C-SUB MAKEMAKE 1 WFC3/UVI ACCUM UVIS2-C5 F350LP 3 none none none 1 N/A S 12C-SUB MAKEMAKE 1 WFC3/UVI ACCUM UVIS2-C5 F350LP 4 none none none 1 N/A S 12C-SUB MAKEMAKE 2 WFC3/UVI ACCUM UVIS2-C5 F350LP 1 none none none 1 N/A S 12C-SUB MAKEMAKE 2 WFC3/UVI ACCUM UVIS2-C5 F350LP 2 none none none 1 N/A S 12C-SUB MAKEMAKE 2 WFC3/UVI ACCUM UVIS2-C5 F350LP 3 none none none 1 N/A S 12C-SUB MAKEMAKE 2 WFC3/UVI ACCUM UVIS2-C5 F350LP 4 none none none 1 N/A S 12C-SUB MAKEMAKE 3 WFC3/UVI ACCUM UVIS2-C5 F350LP 1 none none none 1 N/A S 12C-SUB MAKEMAKE 3 WFC3/UVI ACCUM UVIS2-C5 F350LP 2 none none none 1 N/A S 12C-SUB MAKEMAKE 3 WFC3/UVI ACCUM UVIS2-C5 F350LP 3 none none none 1 N/A S 12C-SUB MAKEMAKE 3 WFC3/UVI ACCUM UVIS2-C5 F350LP 4 none none none 1 N/A S 12C-SUB 18006( 8) - 16-Jan-2026 17:15:41 - [ 6] Visit: 02 (Mirror break) Visit Requirements: AFTER 01 BY 10 D TO 365 D; BETWEEN 16-DEC-2025:08:00:00 AND 17-DEC-2025:16:00:00; BETWEEN 18-DEC-2025:20:00:00 AND 20-DEC-2025:08:00:00; BETWEEN 25-DEC-2025:04:00:00 AND 26-DEC-2025:08:00:00; BETWEEN 28-DEC-2025:00:00:00 AND 29-DEC-2025:08:00:00; BETWEEN 03-JAN-2026:08:00:00 AND 04-JAN-2026:16:00:00; BETWEEN 05-JAN-2026:20:00:00 AND 07-JAN-2026:08:00:00 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 MAKEMAKE WFC3/UVI ACCUM UVIS2-C51 F350LP FLASH=7 1 120 S (480 GS ACQ SCENARIO ONEB1OR; S 2C-SUB S) SEQ 1-3 NON-INT; PATTERN 1 1 ------------------------------------------------------------------------------------------------------------------------------------ 2 MAKEMAKE WFC3/UVI ACCUM UVIS2-C51 F350LP FLASH=7 1 120 S (480 PATTERN 1 2 S 2C-SUB S) ------------------------------------------------------------------------------------------------------------------------------------ 3 MAKEMAKE WFC3/UVI ACCUM UVIS2-C51 F350LP FLASH=7 1 120 S (480 PATTERN 1 3 S 2C-SUB 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 | ------------------------------------------------------------------------------------------------------------------------------------ MAKEMAKE 1 WFC3/UVI ACCUM UVIS2-C5 F350LP 1 none none none 1 N/A S 12C-SUB MAKEMAKE 1 WFC3/UVI ACCUM UVIS2-C5 F350LP 2 none none none 1 N/A S 12C-SUB MAKEMAKE 1 WFC3/UVI ACCUM UVIS2-C5 F350LP 3 none none none 1 N/A S 12C-SUB MAKEMAKE 1 WFC3/UVI ACCUM UVIS2-C5 F350LP 4 none none none 1 N/A S 12C-SUB MAKEMAKE 2 WFC3/UVI ACCUM UVIS2-C5 F350LP 1 none none none 1 N/A S 12C-SUB MAKEMAKE 2 WFC3/UVI ACCUM UVIS2-C5 F350LP 2 none none none 1 N/A S 12C-SUB MAKEMAKE 2 WFC3/UVI ACCUM UVIS2-C5 F350LP 3 none none none 1 N/A S 12C-SUB MAKEMAKE 2 WFC3/UVI ACCUM UVIS2-C5 F350LP 4 none none none 1 N/A S 12C-SUB MAKEMAKE 3 WFC3/UVI ACCUM UVIS2-C5 F350LP 1 none none none 1 N/A S 12C-SUB MAKEMAKE 3 WFC3/UVI ACCUM UVIS2-C5 F350LP 2 none none none 1 N/A S 12C-SUB MAKEMAKE 3 WFC3/UVI ACCUM UVIS2-C5 F350LP 3 none none none 1 N/A S 12C-SUB 18006( 8) - 16-Jan-2026 17:15:41 - [ 7] 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 | ------------------------------------------------------------------------------------------------------------------------------------ MAKEMAKE 3 WFC3/UVI ACCUM UVIS2-C5 F350LP 4 none none none 1 N/A S 12C-SUB 18006( 8) - 16-Jan-2026 17:15:41 - [ 8] Visit: 03 (Nodal constrain 1) Visit Requirements: BETWEEN 12-APR-2026:00:00:00 AND 17-APR-2026:00:00:00; BETWEEN 21-APR-2026:04:00:00 AND 26-APR-2026:04:00:00; BETWEEN 03-APR-2026:04:00:00 AND 07-APR-2026:20:00:00; BETWEEN 25-MAR-2026:00:00:00 AND 30-MAR-2026:00:00:00; BETWEEN 16-MAR-2026:00:00:00 AND 20-MAR-2026:20:00:00; BETWEEN 07-MAR-2026:00:00:00 AND 12-MAR-2026:00:00:00 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 MAKEMAKE WFC3/UVI ACCUM UVIS2-C51 F350LP FLASH=7 1 120 S (480 SEQ 1-3 NON-INT; PATTERN S 2C-SUB S) 1 1 ------------------------------------------------------------------------------------------------------------------------------------ 2 MAKEMAKE WFC3/UVI ACCUM UVIS2-C51 F350LP FLASH=7 1 120 S (480 PATTERN 1 2 S 2C-SUB S) ------------------------------------------------------------------------------------------------------------------------------------ 3 MAKEMAKE WFC3/UVI ACCUM UVIS2-C51 F350LP FLASH=7 1 120 S (480 PATTERN 1 3 S 2C-SUB 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 | ------------------------------------------------------------------------------------------------------------------------------------ MAKEMAKE 1 WFC3/UVI ACCUM UVIS2-C5 F350LP 1 none none none 1 N/A S 12C-SUB MAKEMAKE 1 WFC3/UVI ACCUM UVIS2-C5 F350LP 2 none none none 1 N/A S 12C-SUB MAKEMAKE 1 WFC3/UVI ACCUM UVIS2-C5 F350LP 3 none none none 1 N/A S 12C-SUB MAKEMAKE 1 WFC3/UVI ACCUM UVIS2-C5 F350LP 4 none none none 1 N/A S 12C-SUB MAKEMAKE 2 WFC3/UVI ACCUM UVIS2-C5 F350LP 1 none none none 1 N/A S 12C-SUB MAKEMAKE 2 WFC3/UVI ACCUM UVIS2-C5 F350LP 2 none none none 1 N/A S 12C-SUB MAKEMAKE 2 WFC3/UVI ACCUM UVIS2-C5 F350LP 3 none none none 1 N/A S 12C-SUB MAKEMAKE 2 WFC3/UVI ACCUM UVIS2-C5 F350LP 4 none none none 1 N/A S 12C-SUB MAKEMAKE 3 WFC3/UVI ACCUM UVIS2-C5 F350LP 1 none none none 1 N/A S 12C-SUB MAKEMAKE 3 WFC3/UVI ACCUM UVIS2-C5 F350LP 2 none none none 1 N/A S 12C-SUB MAKEMAKE 3 WFC3/UVI ACCUM UVIS2-C5 F350LP 3 none none none 1 N/A S 12C-SUB MAKEMAKE 3 WFC3/UVI ACCUM UVIS2-C5 F350LP 4 none none none 1 N/A S 12C-SUB 18006( 8) - 16-Jan-2026 17:15:41 - [ 9] Visit: 04 (Nodal constrain 2) Visit Requirements: AFTER 03 BY 9 D TO 365 D; BETWEEN 12-APR-2026:00:00:00 AND 17-APR-2026:00:00:00; BETWEEN 21-APR-2026:04:00:00 AND 26-APR-2026:04:00:00; BETWEEN 03-APR-2026:04:00:00 AND 07-APR-2026:20:00:00; BETWEEN 25-MAR-2026:00:00:00 AND 30-MAR-2026:00:00:00; BETWEEN 16-MAR-2026:00:00:00 AND 20-MAR-2026:20:00:00; BETWEEN 07-MAR-2026:00:00:00 AND 12-MAR-2026:00:00:00 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 MAKEMAKE WFC3/UVI ACCUM UVIS2-C51 F350LP FLASH=7 1 120 S (480 SEQ 1-3 NON-INT; PATTERN S 2C-SUB S) 1 1 ------------------------------------------------------------------------------------------------------------------------------------ 2 MAKEMAKE WFC3/UVI ACCUM UVIS2-C51 F350LP FLASH=7 1 120 S (480 PATTERN 1 2 S 2C-SUB S) ------------------------------------------------------------------------------------------------------------------------------------ 3 MAKEMAKE WFC3/UVI ACCUM UVIS2-C51 F350LP FLASH=7 1 120 S (480 PATTERN 1 3 S 2C-SUB 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 | ------------------------------------------------------------------------------------------------------------------------------------ MAKEMAKE 1 WFC3/UVI ACCUM UVIS2-C5 F350LP 1 none none none 1 N/A S 12C-SUB MAKEMAKE 1 WFC3/UVI ACCUM UVIS2-C5 F350LP 2 none none none 1 N/A S 12C-SUB MAKEMAKE 1 WFC3/UVI ACCUM UVIS2-C5 F350LP 3 none none none 1 N/A S 12C-SUB MAKEMAKE 1 WFC3/UVI ACCUM UVIS2-C5 F350LP 4 none none none 1 N/A S 12C-SUB MAKEMAKE 2 WFC3/UVI ACCUM UVIS2-C5 F350LP 1 none none none 1 N/A S 12C-SUB MAKEMAKE 2 WFC3/UVI ACCUM UVIS2-C5 F350LP 2 none none none 1 N/A S 12C-SUB MAKEMAKE 2 WFC3/UVI ACCUM UVIS2-C5 F350LP 3 none none none 1 N/A S 12C-SUB MAKEMAKE 2 WFC3/UVI ACCUM UVIS2-C5 F350LP 4 none none none 1 N/A S 12C-SUB MAKEMAKE 3 WFC3/UVI ACCUM UVIS2-C5 F350LP 1 none none none 1 N/A S 12C-SUB MAKEMAKE 3 WFC3/UVI ACCUM UVIS2-C5 F350LP 2 none none none 1 N/A S 12C-SUB MAKEMAKE 3 WFC3/UVI ACCUM UVIS2-C5 F350LP 3 none none none 1 N/A S 12C-SUB 18006( 8) - 16-Jan-2026 17:15:41 - [ 10] 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 | ------------------------------------------------------------------------------------------------------------------------------------ MAKEMAKE 3 WFC3/UVI ACCUM UVIS2-C5 F350LP 4 none none none 1 N/A S 12C-SUB 18006( 8) - 16-Jan-2026 17:15:41 - [ 11] Summary Form for Proposal 18006 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures UVIS2-C512C-SUB ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFC3/UVIS ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters FLASH=7 ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements AFTER 01 BY 10 D TO 365 D, AFTER 03 BY 9 D TO 365 D, BETWEEN 01-DEC-2025:00:00:00 AND 02-DEC-2025:00:00:00, BETWEEN 03-APR-2026:04:00:00 AND 07-APR-2026:20:00:00, BETWEEN 03-JAN-2026:08:00:00 AND 04-JAN-2026:16:00:00, BETWEEN 05-JAN-2026:20:00:00 AND 07-JAN-2026:08:00:00, BETWEEN 07-DEC-2025:16:00:00 AND 11-DEC-2025:00:00:00, BETWEEN 07-MAR-2026:00:00:00 AND 12-MAR-2026:00:00:00, BETWEEN 12-APR-2026:00:00:00 AND 17-APR-2026:00:00:00, BETWEEN 16-DEC-2025:08:00:00 AND 17-DEC-2025:16:00:00, BETWEEN 16-DEC-2025:16:00:00 AND 19-DEC-2025:20:00:00, BETWEEN 16-MAR-2026:00:00:00 AND 20-MAR-2026:20:00:00, BETWEEN 18-DEC-2025:20:00:00 AND 20-DEC-2025:08:00:00, BETWEEN 21-APR-2026:04:00:00 AND 26-APR-2026:04:00:00, BETWEEN 25-DEC-2025:04:00:00 AND 26-DEC-2025:08:00:00, BETWEEN 25-DEC-2025:16:00:00 AND 29-DEC-2025:00:00:00, BETWEEN 25-MAR-2026:00:00:00 AND 30-MAR-2026:00:00:00, BETWEEN 28-DEC-2025:00:00:00 AND 29-DEC-2025:08:00:00, GS ACQ SCENARIO ONEB1OR, PATTERN 1 1, PATTERN 1 2, PATTERN 1 3, SEQ 1-3 NON-INT ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F350LP ------------------------------------------------------------------------------------------------------------------------------------ Target Names MAKEMAKE ------------------------------------------------------------------------------------------------------------------------------------