17315( 4) - 03-Jul-2023 15:31:55 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 17315 Version: 4 Check-in Time: 03-Jul-2023 15:31:55 STScI Edit Number: 2 Title Beating Weywot in the game of hide-and-seek ------------------------------------------------------------------------------------ Type Cycle GO/DD 30 ------------------------------------------------------------------------------------ Investigators Contact? PI: Dra. Estela Fernandez-Valenzuela University of Central Florida Board of Y Trustees CoI: Dr. Bryan Jason Holler Space Telescope Science Institute N CoI: Dra. Flavia Luane Rommel Observatorio Nacional N CoI: Dr. Jose Luis Ortiz Instituto de Astrofisica de Andalucia N (IAA) CoI: Mr. Nicolas Morales Instituto de Astrofisica de Andalucia N (IAA) CoI: Dr. Frederic Vachier Observatoire de Paris N CoI: Dr. Felipe Braga-Ribas Universidade Tecnologica Federal do Parana N ------------------------------------------------------------------------------------ Abstract Weywot is the satellite of the trans-Neptunian dwarf planet candidate Quaoar. Obtaining its physical properties, such as size and density, is pivotal in order to understand its formation scenario and to better understand the formation of binary systems in the trans-Neptunian region. Weywot was thought to be a captured satellite due to its estimated size through thermal modeling and its eccentric orbit (which should circularize in a few million years if the satellite formed via collision). However, recent fortuitous detections through stellar occultation indicate that the size could be double. This opens the debate about Weywot's formation. A stellar occultation is predicted to happen on June 22nd that would cross the continental US, providing the opportunity to prepare a good observational campaign to distribute telescopes to maximize the coverage of Weywot's limb (and surroundings). However, our resources are limited and the uncertainty of the current prediction is of around 1000 km north and south the current path. We are therefore asking for a single HST orbit to locate Weywot with respect to Quaoar so that we can reduce the uncertainty to 300 km, thus being able to obtain a highly sampled stellar occultation and decipher the mystery of Weywot's formation. ------------------------------------------------------------------------------------ Observations Description ------------------------ A single orbit is required to image the Quaoar/Weywot TNO binary system with the WFC3/UVIS instrument and the F606W filter. The WFC3-UVIS-BOX-DITHER pattern will be used, which is composed of 4 exposures. Each exposure will be 432 seconds long in order to optimize the efficiency of the orbit (resulting in only 3 seconds of unused time). This individual exposure time is longer than the 348-second limit under which a serial buffer dump is required and APT does not provide a warning message about adding a post-flash. 17315( 4) - 03-Jul-2023 15:31:55 - [ 2] The "UVIS2" aperture was specified to ensure optimal placement within the UVIS2 detector, which has better characteristics than UVIS1. A BEFORE special requirement is specified to ensure the observations occur before June 19th. There is an occultation by Weywot predicted on June 22nd and obtaining the data by June 19th will allow enough time to process the data. extract astrometry, and update the prediction. This timing requirement was included in the DDT proposal. ------------------------------------------------------------------------------------ 17315( 4) - 03-Jul-2023 15:31:55 - [ 3] TARGET LIST Solar System Targets ------------------------------------------------------------------------------------------------------------------------------------ TARGET NUMBER: 1 TARGET NAME: QUAOAR ------------------------------------------------------------------------------------------------------------------------------------ TARGET DESCRIPTION: ASTEROID Trans-Neptunian object (TNO) ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 1 TARGET POSITION LEVEL 2 TYPE=ASTEROID, A=43.35614180031197, E=0.0399368787562926, I=7.991290702148744 , O=189.0991840859715, W=158.6090073041173, M=293.8088571674838, EQUINOX=J2000, EPOCH=25-MAY-2023:00:00:00, EpochTimeScale=TDB ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 3 WINDOWS ------------------------------------------------------------------------------------------------------------------------------------ DATA COMMENTS V = 18.9 Ephemeris Center: EARTH Extended: NO ------------------------------------------------------------------------------------------------------------------------------------ 17315( 4) - 03-Jul-2023 15:31:55 - [ 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 ------------------------------------------------------------------------------------------------------------------------------------ 17315( 4) - 03-Jul-2023 15:31:55 - [ 5] Visit: 01 (Observation 1) Visit Requirements: BEFORE 19-JUN-2023:00:00:00 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 QUAOAR WFC3/UVI ACCUM UVIS2 F606W 1 432 S SEQ 1 NON-INT; PATTERN 1 S (1728 S) 1 ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ QUAOAR 1 WFC3/UVI ACCUM UVIS2 F606W 1 none none none tbd N/A S QUAOAR 1 WFC3/UVI ACCUM UVIS2 F606W 2 none none none tbd N/A S QUAOAR 1 WFC3/UVI ACCUM UVIS2 F606W 3 none none none tbd N/A S QUAOAR 1 WFC3/UVI ACCUM UVIS2 F606W 4 none none none tbd N/A S 17315( 4) - 03-Jul-2023 15:31:55 - [ 6] Summary Form for Proposal 17315 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures UVIS2 ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFC3/UVIS ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements BEFORE 19-JUN-2023:00:00:00, PATTERN 1 1, SEQ 1 NON-INT ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F606W ------------------------------------------------------------------------------------------------------------------------------------ Target Names QUAOAR ------------------------------------------------------------------------------------------------------------------------------------