15379( 17) - 15-Dec-2017 00:44:22 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 15379 Version: 17 Check-in Time: 15-Dec-2017 00:44:22 STScI Edit Number: 13 Title Characterizing Enigmatic Phaethon in the UV ------------------------------------------------------------------------------------ Type Cycle GO/DD 25 ------------------------------------------------------------------------------------ Investigators Contact? PI: Dr. Amanda R. Hendrix Planetary Science Institute Y CoI: Dr. Humberto Campins University of Central Florida N CoI: Dr. Faith Vilas Planetary Science Institute N ------------------------------------------------------------------------------------ Abstract (3200) Phaethon is a curious object: just 5 km in diameter, it is a near-Earth asteroid that shows signs of being active and is the parent body of the Geminid meteor stream. Phaethon is a B-class asteroid, as is Bennu, the target of the upcoming NASA OSIRIS-REx mission. As a B-class asteroid, Phaethon is linked with carbonaceous species and phyllosilicates; both of these types of materials exhibit diagnostic spectral features in the UV, yet Phaethon has not been observed deep in the UV. Phaethon's UV-visible observations (near 400 nm) suggest spectral variability, spatially and/or temporally. In December 2017, Phaethon will be at its closest approach to Earth in decades. We propose 2 orbits of DD time to observe Phaethon for the first time using STIS deep in the UV to investigate the 400 nm region (potentially diagnostic of phyllosilicates), characterize its spectral shape deeper in the UV (to look for carbon signatures) and to understand the spectral character of Phaethon for better understanding of OSIRIS-REx target Bennu. UV-visible laboratory measurements of candidate materials will be made through our recently-selected NASA SSERVI program, for comparison with Phaethon STIS data. ------------------------------------------------------------------------------------ Observations Description ------------------------ Our goal is to observe Phaethon using the STIS G140L (115-174 nm), G230L (157-318 nm) and G430L (290-570 nm) gratings to obtain full spectral coverage in the ~100-570 nm range, gaining new insights into Phaethon's surface composition and possible activity, investigating its UV absorption edge and spectral shape, and ensuring spectral overlap with existing ground-based data. We will employ the strategies we used for our Ceres program (13693), observing Phaethon in 2 HST orbits. On Dec 9 2017, Phaethon will be 0.043arcsec in diameter and the solar phase angle will be ~19.6deg; the apparent size increases with time up until Dec 17, when it reaches 0.1arcsec; the phase angle also increases in this period as Phaethon approaches periapsis, to 65.7deg on Dec 17. Ideally our STIS observations would occur at a sweet spot between angular size and phase angle. 15379( 17) - 15-Dec-2017 00:44:22 - [ 2] In our ETC calculations, we find that the best opportunities to maximize UV SNR, while not getting close to saturating the CCD, are on Dec 14-15. We have run ETC based on our experience observing Ceres, which has a similar albedo (Ceres' albedo is ~0.08 compared to Phaethon's of ~0.11, but the Phaethon phase angle will be higher than Ceres'). Though we don't expect Phaethon's spectral shape to match Ceres', we expect that using Ceres' spectral shape in ETC is a good enough approximation to make sure that the CCD isn't saturated and MAMA count rates are not exceeded. As with the Cycle 22 Ceres observations, we will combine the spectra from each grating into a composite spectrum. The G140L data will be critical for testing whether a Ceres-like bump near 160 nm is observed; the G430L data will be used to confirm the spectral shape in this contentious region and possibly look for spatial variations if the timing of the two HST orbits occurs such that different hemispheres of Phaethon are observed (Phaethon's rotational period is 3.6 hr); the G230L spectra are important for connecting the G140L and G430L regions and understanding the overall spectral shape. We can achieve the required spectral coverage using 2 2-sec G430L exposures, along with 2 700-sec G230L exposures on one orbit; on the second orbit we will do one ~2000-sec G140L exposure plus 2 more 2-sec G430L exposures. We will use the 0.1arcsec slit. Our ETC estimates indicate that the G140L SNR will be even higher for Phaethon than for Ceres, demonstrating the excellent quality of this observing opportunity. ------------------------------------------------------------------------------------ 15379( 17) - 15-Dec-2017 00:44:22 - [ 3] TARGET LIST Solar System Targets ------------------------------------------------------------------------------------------------------------------------------------ TARGET NUMBER: 1 TARGET NAME: PHAETHON ------------------------------------------------------------------------------------------------------------------------------------ TARGET DESCRIPTION: ASTEROID Asteroid 3200 Phaethon ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 1 TARGET POSITION LEVEL 2 TYPE=ASTEROID, A=1.271276492594683, E=0.890010915974444, I=22.19847903363508, O=265.3465654874296, W=322.0555020924195, M=139.754587559709, EQUINOX=J2000, EPOCH=17-JUN-2011:00:00:00, EpochTimeScale=TDB ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 3 WINDOWS ------------------------------------------------------------------------------------------------------------------------------------ DATA COMMENTS V = 13.9 +/- 0.1 Ephemeris Center: EARTH Extended: YES ------------------------------------------------------------------------------------------------------------------------------------ TARGET NUMBER: 2 TARGET NAME: PHAETHON-COPY ------------------------------------------------------------------------------------------------------------------------------------ TARGET DESCRIPTION: ASTEROID Asteroid 3200 Phaethon ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 1 TARGET POSITION LEVEL 2 TYPE=ASTEROID, A=1.271276492594683, E=0.890010915974444, I=22.19847903363508, O=265.3465654874296, W=322.0555020924195, M=139.754587559709, EQUINOX=J2000, EPOCH=17-JUN-2011:00:00:00, EpochTimeScale=TDB ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 3 WINDOWS ------------------------------------------------------------------------------------------------------------------------------------ DATA COMMENTS V = 13.9 +/- 0.1 Ephemeris Center: HUBBLE Extended: YES ------------------------------------------------------------------------------------------------------------------------------------ 15379( 17) - 15-Dec-2017 00:44:22 - [ 4] TARGET LIST Solar System Targets ------------------------------------------------------------------------------------------------------------------------------------ TARGET NUMBER: 3 TARGET NAME: PHAETHON-NEW ------------------------------------------------------------------------------------------------------------------------------------ TARGET DESCRIPTION: ASTEROID 3200 PHAETHON ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 1 TARGET POSITION LEVEL 2 TYPE=ASTEROID, A=1.271276492594683, E=0.890010915974444, I=22.19847903363508, O=265.3465654874296, W=322.0555020924195, M=139.754587559709, EQUINOX=J2000, EPOCH=17-JUN-2011:00:00:00, EpochTimeScale=TDB ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 3 WINDOWS ------------------------------------------------------------------------------------------------------------------------------------ DATA COMMENTS V = 11.1 +/- 0.1 Ephemeris Center: HUBBLE ------------------------------------------------------------------------------------------------------------------------------------ 15379( 17) - 15-Dec-2017 00:44:22 - [ 5] Visit: 01 Visit Requirements: BETWEEN 29-NOV-2017:00:00:00 AND 01-DEC-2017:00:00:00 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 PHAETHON-CO STIS/CCD ACQ F28X50LP MIRROR DIFFUSE-CENTER=GEOMETRIC-CENTE 1 0.5 S (0.5 PY R, S) ACQTYPE=DIFFUSE, CHECKBOX=3.0 ------------------------------------------------------------------------------------------------------------------------------------ 2 PHAETHON-CO STIS/CCD ACCUM 52X0.2 G430L 4300 1 10 S PY see below (4 S) ------------------------------------------------------------------------------------------------------------------------------------ 3 PHAETHON-CO STIS/NUV ACCUM 52X0.2 G230L 2376 1 800 S PY -MAMA see below (777 S) ------------------------------------------------------------------------------------------------------------------------------------ 4 PHAETHON-CO STIS/NUV ACCUM 52X0.2 G230L 2376 1 800 S PY -MAMA see below (777 S) ------------------------------------------------------------------------------------------------------------------------------------ 5 PHAETHON-CO STIS/CCD ACCUM 52X0.2 G430L 4300 1 10 S PY see below (4 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 | ------------------------------------------------------------------------------------------------------------------------------------ PHAETHON-COPY 1 STIS/CCD ACQ F28X50LP MIRROR none none none none 1 N/A PHAETHON-COPY 2 STIS/CCD ACCUM 52X0.2 G430L 4300 none none none 1 1 2.0 S PHAETHON-COPY 2 STIS/CCD ACCUM 52X0.2 G430L 4300 none none none 2 1 2.0 S PHAETHON-COPY 3 STIS/NUV ACCUM 52X0.2 G230L 2376 none none none none 1 777.0 S -MAMA PHAETHON-COPY 4 STIS/NUV ACCUM 52X0.2 G230L 2376 none none none none 1 777.0 S -MAMA PHAETHON-COPY 5 STIS/CCD ACCUM 52X0.2 G430L 4300 none none none 1 1 2.0 S PHAETHON-COPY 5 STIS/CCD ACCUM 52X0.2 G430L 4300 none none none 2 1 2.0 S 15379( 17) - 15-Dec-2017 00:44:22 - [ 6] Visit: 02 Visit Requirements: BETWEEN 30-NOV-2017:00:00:00 AND 01-DEC-2017:00:00:00 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 PHAETHON STIS/CCD ACQ F28X50LP MIRROR ACQTYPE=DIFFUSE, CHECKBOX=3.0, 1 0.5 S (0.5 DIFFUSE-CENTER=GEOMETRIC-CENTE S) R ------------------------------------------------------------------------------------------------------------------------------------ 2 PHAETHON STIS/FUV ACCUM 52X0.2 G140L 1425 1 2260 S -MAMA (2260 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 | ------------------------------------------------------------------------------------------------------------------------------------ PHAETHON 1 STIS/CCD ACQ F28X50LP MIRROR none none none none 1 N/A PHAETHON 2 STIS/FUV ACCUM 52X0.2 G140L 1425 none none none none 1 N/A -MAMA 15379( 17) - 15-Dec-2017 00:44:22 - [ 7] Visit: 51 Visit Requirements: SCHED 100%; ORIENT 67.0D TO 67.0 D 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 PHAETHON-NE S/C POINTIN V1 1 1 S (1 S) POS TARG -213.6796, W G -224.8351; SAA CONTOUR 24; GSPAIR N0PT000271F20000000000F0 ; GS ACQ SCENARIO ONEB1B3; SEQ 1-7 NON-INT ------------------------------------------------------------------------------------------------------------------------------------ 2 PHAETHON-NE STIS/CCD ACQ F28X50OII MIRROR DIFFUSE-CENTER=GEOMETRIC-CENTE 1 4 S (4 S) NEW OBSET; NEW W R, ALIGNMENT; EXP PCS MODE ACQTYPE=DIFFUSE, CHECKBOX=3.0 GYRO ------------------------------------------------------------------------------------------------------------------------------------ 3 PHAETHON-NE STIS/CCD ACCUM 52X2 G430L 4300 1 2 S (2 S) EXP PCS MODE GYRO W ------------------------------------------------------------------------------------------------------------------------------------ 4 PHAETHON-NE STIS/CCD ACCUM 52X2 G230LB 2375 1 150 S (150 NEW ALIGNMENT; EXP PCS W S) MODE GYRO ------------------------------------------------------------------------------------------------------------------------------------ 5 PHAETHON-NE STIS/CCD ACCUM 52X2 G230LB 2375 1 150 S (150 NEW ALIGNMENT; EXP PCS W S) MODE GYRO ------------------------------------------------------------------------------------------------------------------------------------ 6 PHAETHON-NE STIS/CCD ACCUM 52X2 G430L 4300 1 2 S (2 S) NEW ALIGNMENT; EXP PCS W MODE GYRO ------------------------------------------------------------------------------------------------------------------------------------ 7 PHAETHON-NE STIS/CCD ACCUM 52X2 G230LB 2375 1 150 S (150 NEW ALIGNMENT; EXP PCS W S) MODE GYRO ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ PHAETHON-NEW 1 S/C POINTIN V1 none none none none tbd N/A G PHAETHON-NEW 2 STIS/CCD ACQ F28X50OI MIRROR none none none none tbd N/A I PHAETHON-NEW 3 STIS/CCD ACCUM 52X2 G430L 4300 none none none 1 tbd N/A PHAETHON-NEW 3 STIS/CCD ACCUM 52X2 G430L 4300 none none none 2 tbd N/A PHAETHON-NEW 4 STIS/CCD ACCUM 52X2 G230LB 2375 none none none 1 tbd N/A PHAETHON-NEW 4 STIS/CCD ACCUM 52X2 G230LB 2375 none none none 2 tbd N/A PHAETHON-NEW 5 STIS/CCD ACCUM 52X2 G230LB 2375 none none none 1 tbd N/A 15379( 17) - 15-Dec-2017 00:44:22 - [ 8] 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 | ------------------------------------------------------------------------------------------------------------------------------------ PHAETHON-NEW 5 STIS/CCD ACCUM 52X2 G230LB 2375 none none none 2 tbd N/A PHAETHON-NEW 6 STIS/CCD ACCUM 52X2 G430L 4300 none none none 1 tbd N/A PHAETHON-NEW 6 STIS/CCD ACCUM 52X2 G430L 4300 none none none 2 tbd N/A PHAETHON-NEW 7 STIS/CCD ACCUM 52X2 G230LB 2375 none none none 1 tbd N/A PHAETHON-NEW 7 STIS/CCD ACCUM 52X2 G230LB 2375 none none none 2 tbd N/A 15379( 17) - 15-Dec-2017 00:44:22 - [ 9] Summary Form for Proposal 15379 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures 52X0.2, 52X2, F28X50LP, F28X50OII, V1 ------------------------------------------------------------------------------------------------------------------------------------ Configurations S/C, STIS/CCD, STIS/FUV-MAMA, STIS/NUV-MAMA ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM, ACQ, POINTING ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters ACQTYPE=DIFFUSE, CHECKBOX=3.0, DIFFUSE-CENTER=GEOMETRIC-CENTER ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements BETWEEN 29-NOV-2017:00:00:00 AND 01-DEC-2017:00:00:00, BETWEEN 30-NOV-2017:00:00:00 AND 01-DEC-2017:00:00:00, EXP PCS MODE GYRO, GS ACQ SCENARIO ONEB1B3, GSPAIR N0PT000271F20000000000F0, NEW ALIGNMENT, NEW OBSET, ORIENT 67.0D TO 67.0 D, POS TARG -213.6796, -224.8351, SAA CONTOUR 24, SCHED 100%, SEQ 1-7 NON-INT ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements G140L, G230L, G230LB, G430L, MIRROR ------------------------------------------------------------------------------------------------------------------------------------ Target Names PHAETHON, PHAETHON-COPY, PHAETHON-NEW ------------------------------------------------------------------------------------------------------------------------------------