15142( 3) - 08-Mar-2018 16:47:17 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 15142 Version: 3 Check-in Time: 08-Mar-2018 16:47:17 STScI Edit Number: 1 Title Orbit of a Resolved Trojan Binary ------------------------------------------------------------------------------------ Type Cycle GO 25 ------------------------------------------------------------------------------------ Investigators Contact? PI: Dr. Keith S. Noll NASA Goddard Space Flight Center Y CoI: Dr. Will M. Grundy Lowell Observatory N CoI: Dr. Harold F. Levison Southwest Research Institute N ------------------------------------------------------------------------------------ Abstract We have identified the Jupiter Trojan (16974) 1998 WR21 as a binary, making it only the third known resolvable binary in this population. We will use HST to determine its orbit from which we will determine the system mass. Using the mass and WISE-derived albedo, we will derive the density. Density can be used to constrain planetary migration models; low density is characteristic of bodies found in the Kuiper Belt, a remnant of the solar system's protoplanetary disk. Only one undisputed density has been measured in the Trojans, that of the binary (617) Patroclus, which has a low density of 800 kg/m3. The density of WR21 will test whether Patroclus is an anomaly or whether low densities might be the norm, as they are in the Kuiper Belt. ------------------------------------------------------------------------------------ Observations Description ------------------------ Five single orbit visits to 1998 WR21 spaced at the presumed synchronous orbital period. Timings spaced at 1/5 fractional orbit phase. Integer full phase(s) can occur between visits. ------------------------------------------------------------------------------------ 15142( 3) - 08-Mar-2018 16:47:17 - [ 2] TARGET LIST Solar System Targets ------------------------------------------------------------------------------------------------------------------------------------ TARGET NUMBER: 1 TARGET NAME: TROJAN16974 ------------------------------------------------------------------------------------------------------------------------------------ TARGET DESCRIPTION: ASTEROID Trojan Asteroid (16974) 1998 WR21 ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 1 TARGET POSITION LEVEL 2 TYPE=ASTEROID, A=5.203807061689808, E=0.06936961003515499, I=15.01910777363845, O=241.5969712074684, W=136.4884726334601, M=72.59450393874381, EQUINOX=J2000, EPOCH=27-JAN-2012:00:00:00, EpochTimeScale=TDB ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 3 WINDOWS RANGE EARTH TROJAN16974 LT 4.50 ------------------------------------------------------------------------------------------------------------------------------------ DATA COMMENTS V = 17.5 +/- 0.5 Ephemeris Center: EARTH ------------------------------------------------------------------------------------------------------------------------------------ 15142( 3) - 08-Mar-2018 16:47:17 - [ 3] 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 ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 2 Primary_Pattern Secondary_Pattern Pattern_Type WFC3-UVIS-DITHER-LINE Pattern_Purpose DITHER Number_Of_Points 2 Point_Spacing 0.145 Line_Spacing Coordinate_Frame POS-TARG Pattern_Orient 46.84 Angle_Between_Sides Center_Pattern NO ------------------------------------------------------------------------------------------------------------------------------------ 15142( 3) - 08-Mar-2018 16:47:17 - [ 4] Visit: 01 Visit Requirements: On Hold Comments: Additional Comments: First visit can schedule at any time, t_1, in the range window (better early in the window for flexibility). Subsequent visits should schedule at a time defined by: t_n = t_1 + (n+f)*78.9 hr where n is an integer from 0 to 10 (upper limit to avoid accumulating period uncertainty error) and f is a fraction that is different for each visit in the following sequence visit f err 1 0 n/a 2 0.2 +/-0.05 3 0.4 +/-0.05 4 0.6 +/-0.05 5 0.8 +/-0.05 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 TROJAN16974 WFC3/UVI ACCUM UVIS2-M51 F555W FLASH=11 2 50 S (400 GS ACQ SCENARIO BASE1B3; S 2C-SUB S) PATTERN 1 1 ------------------------------------------------------------------------------------------------------------------------------------ 2 TROJAN16974 WFC3/UVI ACCUM UVIS2-M51 F438W FLASH=11 1 160 S (320 PATTERN 2 2-4 S 2C-SUB S) ------------------------------------------------------------------------------------------------------------------------------------ 3 TROJAN16974 WFC3/UVI ACCUM UVIS2-M51 F814W FLASH=11 1 80 S (160 S 2C-SUB S) ------------------------------------------------------------------------------------------------------------------------------------ 4 TROJAN16974 WFC3/UVI ACCUM UVIS2-M51 F336W FLASH=11 1 300 S (600 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 | ------------------------------------------------------------------------------------------------------------------------------------ TROJAN16974 1 WFC3/UVI ACCUM UVIS2-M5 F555W 1 none 1 none 1 N/A S 12C-SUB TROJAN16974 1 WFC3/UVI ACCUM UVIS2-M5 F555W 1 none 2 none 1 N/A S 12C-SUB TROJAN16974 1 WFC3/UVI ACCUM UVIS2-M5 F555W 2 none 1 none 1 N/A S 12C-SUB TROJAN16974 1 WFC3/UVI ACCUM UVIS2-M5 F555W 2 none 2 none 1 N/A S 12C-SUB 15142( 3) - 08-Mar-2018 16:47:17 - [ 5] 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 | ------------------------------------------------------------------------------------------------------------------------------------ TROJAN16974 1 WFC3/UVI ACCUM UVIS2-M5 F555W 3 none 1 none 1 N/A S 12C-SUB TROJAN16974 1 WFC3/UVI ACCUM UVIS2-M5 F555W 3 none 2 none 1 N/A S 12C-SUB TROJAN16974 1 WFC3/UVI ACCUM UVIS2-M5 F555W 4 none 1 none 1 N/A S 12C-SUB TROJAN16974 1 WFC3/UVI ACCUM UVIS2-M5 F555W 4 none 2 none 1 N/A S 12C-SUB TROJAN16974 2 WFC3/UVI ACCUM UVIS2-M5 F438W 1 none none none 1 N/A S 12C-SUB TROJAN16974 2 WFC3/UVI ACCUM UVIS2-M5 F438W 2 none none none 1 N/A S 12C-SUB TROJAN16974 3 WFC3/UVI ACCUM UVIS2-M5 F814W 1 none none none 1 N/A S 12C-SUB TROJAN16974 3 WFC3/UVI ACCUM UVIS2-M5 F814W 2 none none none 1 N/A S 12C-SUB TROJAN16974 4 WFC3/UVI ACCUM UVIS2-M5 F336W 1 none none none 1 N/A S 12C-SUB TROJAN16974 4 WFC3/UVI ACCUM UVIS2-M5 F336W 2 none none none 1 N/A S 12C-SUB 15142( 3) - 08-Mar-2018 16:47:17 - [ 6] Visit: 02 Visit Requirements: On Hold Comments: Additional Comments: this visit should follow visit 1 by (n + 0.2 +/-0.05) * 78.9 hrs where n is an integer On Hold Comments: Additional Comments: this visit should follow visit 1 by (n + 0.4 +/-0.05) * 78.9 hrs where n is an integer On Hold Comments: Additional Comments: this visit should follow visit 1 by (n + 0.6 +/-0.05) * 78.9 hrs where n is an integer On Hold Comments: Additional Comments: this visit should follow visit 1 by (n + 0.8 +/-0.05) * 78.9 hrs where n is an integer