15259( 2) - 20-Jul-2017 21:05:53 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 15259 Version: 2 Check-in Time: 20-Jul-2017 21:05:53 STScI Edit Number: 0 Title UV Spectroscopy of Lucy Mission Targets ------------------------------------------------------------------------------------ Type Cycle GO 25 ------------------------------------------------------------------------------------ Investigators Contact? PI: Dr. Cristina Thomas Planetary Science Institute Y CoI: Dr. Keith S. Noll NASA Goddard Space Flight Center N CoI: Dr. Joshua P Emery University of Tennessee at Knoxville N ------------------------------------------------------------------------------------ Abstract The Trojan asteroids are a significant population of primitive bodies trapped in Jupiter's stable L4 and L5 Lagrange regions. Their physical properties and existence in these particular orbits constrain the chemical and dynamical processes in our early Solar System. NASA's recently selected Lucy mission will perform the first reconnaissance of these asteroids and will answer many fundamental questions about the population. The compositions of the Trojans are not well understood. Spectroscopy and spectrophotometry in visible and near-infrared wavelengths show red slopes (spectra with reflectivity increasing towards the long wavelength end of the spectrum) and no diagnostic spectral absorption features. However, past spectral and photometric observations suggest there are unobserved features in ultraviolet wavelengths. We propose to obtain ultraviolet spectroscopy with WFC3 of four Trojan asteroids that are targets of the Lucy mission. Lucy will not have the capability to obtain ultraviolet spectra. The proposed observations can only be made using Hubble. We will determine if there are UV spectral features, as suggested by visible wavelength observations, and connect these features to candidate compositional components. These observations will enable connections between the compositions of Trojans and dynamical models of the early Solar System. ------------------------------------------------------------------------------------ Observations Description ------------------------ During Cycle 25, we will obtain UV spectra of 2 Jovian Trojan asteroids that are targets of NASA's recently selected Lucy mission: (617) Patroclus and (11351) Leucus. Another two targets, (3548) Eurybates and (21900) Orus, will be observed in Cycle 26. Together, these objects span the range of compositions observed in the Trojan population. The proposed targets span three spectral types (C, D, P) and include members of the "red" and "less red" spectral groups. We will observe these objects with the Wide Field Camera 3 UVIS configuration with the G280 spectral element and F300X for the complementary direct imaging. The wavelength range provided by the G280 spectral element (200-400 nm, spectral resolution of ~70) will complement the visible spectroscopy data already available for Trojan asteroids from ground based observatories. This instrument configuration was also chosen because its resolution and throughput 15259( 2) - 20-Jul-2017 21:05:53 - [ 2] enable observations of appropriate signal-to-noise to be done efficiently for each object. Our required signal-to noise ratio (SNR) as ~50 at 3000 Angstroms. We have two scientific goals which define our observing requirements: (1) examining the downturn toward the UV (~0.43 microns) that is suggestive of an unobserved UV spectral feature for less-red objects and (2) searching for absorption features that are diagnostic of volatiles, organics, and salts. This SNR requirement guarantees adequate signal to noise in the spectral region ~0.4 microns where the downturn has been observed previously and near the spectral features observed on other small bodies. By setting our SNR requirements at 3000 Angstroms, we avoid the sharp dropoff in flux at shorter wavelengths which would dramatically increase our required exposure time. We used the Wide Field Camera 3 Spectroscopic Exposure Time Calculator (ETC) to determine our total exposure times for each object. Each calculation used a point source and the HST Solar Spectrum spectral distribution. In order to give a conservative estimate of SNR, we used high values for standard zodiacal light normalizations, standard earth shine light normalizations, and air glow. The target ephemerides were examined in Aladin for a period when the object is brightest and can be observed with HST during Cycle 25. The magnitudes calculated by JPL Horizons are determined using the object's H (Solar System absolute magnitude) value. These values are subject to uncertainties resulting from the rotational light curves of the targets. Therefore, we need to take into consideration the light curve variation for each target. In order to calculate the minimum SNR for the observing window, we add the maximum light curve variation from the Minor Planet Center Lightcurve Database (http://www.minorplanetcenter.net/iau/lists/LightcurveDat.html) to the predefined faintest magnitude. This precaution gives us conservative estimates which guarantee acceptable SNR. (617) Patroclus requires a single orbit and (11351) Leucus requires two orbits. For our defined sequence, we use two dither positions. We take a direct image with SNR>50 for Patroclus and SNR>30 for Leucus and the total exposure time at each object is determined by the time available in each orbit. The observing window is defined by the SNR>50 at 3000 Angstrom requirement. (617) Patroclus, 1 orbit Patroclus is a less red P-type object. Patroclus can be observed with V<16.1 (lightcurve corrected to V<16.22) from Feb 2 to Apr 8 2018. With a total spectral exposure time of t=1924s, we expect SNR~98 at 3000 Angstroms. Patroclus is known to be a binary system (e.g., Marchis et al. 2006). Component resolved spectroscopic observations (H+K, 1.45-2.45 micron) of the Patroclus binary system demonstrate that the two components have identical reflectance spectra (Marchis et al. 2013). Therefore, we do not require a specific orientation of the system for the observation. (11351) Leucus, 2 orbits Leucus is a D-type object. Leucus can be observed with V<17.86 from Jul 23 to Aug 20 2018. With a total exposure time of t=4228s, we expect SNR~49 at 3000 Angstroms. ------------------------------------------------------------------------------------ 15259( 2) - 20-Jul-2017 21:05:53 - [ 3] TARGET LIST Solar System Targets ------------------------------------------------------------------------------------------------------------------------------------ TARGET NUMBER: 1 TARGET NAME: 617-PATROCLUS ------------------------------------------------------------------------------------------------------------------------------------ TARGET DESCRIPTION: ASTEROID Binary, LR R-type ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 1 TARGET POSITION LEVEL 2 TYPE=ASTEROID, A=5.218499694553197, E=0.1399500456355474, I=22.05269861079197, O=44.36596299545594, W=307.8595259822105, M=325.1954514012491, EQUINOX=J2000, EPOCH=08-JUN-2011:00:00:00, EpochTimeScale=TDB ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 3 WINDOWS ------------------------------------------------------------------------------------------------------------------------------------ DATA COMMENTS V = 16.22 +/- 0.12 Ephemeris Center: EARTH Extended: NO ------------------------------------------------------------------------------------------------------------------------------------ TARGET NUMBER: 2 TARGET NAME: 11351-LEUCUS ------------------------------------------------------------------------------------------------------------------------------------ TARGET DESCRIPTION: ASTEROID D-type ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 1 TARGET POSITION LEVEL 2 TYPE=ASTEROID, A=5.266769639519152, E=0.06613217986623902, I=11.56549052270034, O=251.0869371990501, W=160.0963195215948, M=66.311200245168, EQUINOX=J2000, EPOCH=29-SEP-2011:00:00:00, EpochTimeScale=TDB ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 3 WINDOWS ------------------------------------------------------------------------------------------------------------------------------------ DATA COMMENTS V = 17.17 +/- 0.18 Ephemeris Center: EARTH Extended: NO ------------------------------------------------------------------------------------------------------------------------------------ 15259( 2) - 20-Jul-2017 21:05:53 - [ 4] Visit: 01 (Patroclus) Visit Requirements: BETWEEN 14-FEB-2018:00:00:00 AND 19-FEB-2018:22:00:00; BETWEEN 21-FEB-2018:00:00:00 AND 26-FEB-2018:22:00:00; BETWEEN 01-MAR-2018:00:00:00 AND 02-MAR-2018:06:00:00; BETWEEN 03-MAR-2018:00:00:00 AND 05-MAR-2018:00:00:00; BETWEEN 09-MAR-2018:00:00:00 AND 11-MAR-2018:00:00:00; BETWEEN 12-MAR-2018:00:00:00 AND 13-MAR-2018:22:00:00; BETWEEN 15-MAR-2018:00:00:00 AND 23-MAR-2018:12:00:00; BETWEEN 24-MAR-2018:12:00:00 AND 27-MAR-2018:12:00:00; BETWEEN 04-FEB-2018:12:00:00 AND 11-FEB-2018:12:00:00; BETWEEN 29-MAR-2018:00:00:00 AND 30-MAR-2018:00:00:00; BETWEEN 31-MAR-2018:00:00:00 AND 08-APR-2018:00:00:00 On Hold Comments: Additional Comments: This observation is organized as followed: 1. Direct Image A. exposure time=25 seconds. post flash=12 Pos Targ X=0, Y=-50 to get it in the center of chip 2. 2. Spec 1. exposure time=962 seconds, cr_split=2. Pos Targ X=0, Y=-50. dither= 13x distance of WFC3-UVIS-DITHER-LINE. (point spacing 0.145 x 13= 1.885") 3. Spec 2. exposure time=962 seconds, cr_split=2. Pos Targ X=1.287, Y=-48.622 4. Direct Image A. exposure time=25 seconds. post flash=12 Pos Targ X=1.287, Y=-48.622 1 & 2 are at the same position, 3 & 4 are at the same position. These are paired to place the direct image in the same location as the dispersed images. The observability windows are dictated by V<16.1 (with lightcurve added V<16.22). This window opens on Feb 2 and closes on Apr 8 2018. The specific windows were determined by investigating when other bright and/or numerous objects would be in the field. Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exp | Target | Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Num | Name | Config | Mode | or FOV |Element |Waveln.| Parameters |Exp| (Total) | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 617-PATROCL WFC3/UVI ACCUM G280-REF F300X FLASH=12 1 25 S (25 POS TARG null, -50; SEQ US S S) 1-4 NON-INT ------------------------------------------------------------------------------------------------------------------------------------ 2 617-PATROCL WFC3/UVI ACCUM UVIS G280 CR-SPLIT=2 1 962 S (962 POS TARG null, -50 US S S) ------------------------------------------------------------------------------------------------------------------------------------ 3 617-PATROCL WFC3/UVI ACCUM UVIS G280 CR-SPLIT=2 1 962 S (962 POS TARG 1.287, -48.622 US S S) ------------------------------------------------------------------------------------------------------------------------------------ 4 617-PATROCL WFC3/UVI ACCUM G280-REF F300X FLASH=12 1 25 S (25 POS TARG 1.287, -48.622 US S S) ------------------------------------------------------------------------------------------------------------------------------------ 15259( 2) - 20-Jul-2017 21:05:53 - [ 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 | ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ 617-PATROCLUS 1 WFC3/UVI ACCUM G280-REF F300X none none none none 1 N/A S 617-PATROCLUS 2 WFC3/UVI ACCUM UVIS G280 none none none 1 1 N/A S 617-PATROCLUS 2 WFC3/UVI ACCUM UVIS G280 none none none 2 1 N/A S 617-PATROCLUS 3 WFC3/UVI ACCUM UVIS G280 none none none 1 1 N/A S 617-PATROCLUS 3 WFC3/UVI ACCUM UVIS G280 none none none 2 1 N/A S 617-PATROCLUS 4 WFC3/UVI ACCUM G280-REF F300X none none none none 1 N/A S 15259( 2) - 20-Jul-2017 21:05:53 - [ 6] Visit: 02 (Leucus) Visit Requirements: BETWEEN 17-AUG-2018:00:00:00 AND 17-AUG-2018:06:00:00; BETWEEN 18-AUG-2018:01:00:00 AND 19-AUG-2018:00:00:00; BETWEEN 19-AUG-2018:12:00:00 AND 19-AUG-2018:18:00:00; BETWEEN 20-AUG-2018:12:00:00 AND 21-AUG-2018:12:00:00; BETWEEN 07-AUG-2018:00:00:00 AND 08-AUG-2018:00:00:00; BETWEEN 08-AUG-2018:11:00:00 AND 08-AUG-2018:15:00:00; BETWEEN 11-AUG-2018:14:00:00 AND 13-AUG-2018:14:00:00; BETWEEN 31-JUL-2018:12:00:00 AND 01-AUG-2018:12:00:00; BETWEEN 02-AUG-2018:06:00:00 AND 02-AUG-2018:16:00:00 On Hold Comments: Additional Comments: This observation is organized as followed: Orbit 1: 1. Direct Image A. exposure time=60 seconds. post flash=12 Pos Targ X=0, Y=-50 to get it in the center of chip 2. 2. Spec 1. exposure time=2115 seconds, cr_split=2. Pos Targ X=0, Y=-50. Orbit 2: dither= 13x distance of WFC3-UVIS-DITHER-LINE. (point spacing 0.145 x 13= 1.885") 3. Spec 2. exposure time=2115 seconds, cr_split=2. Pos Targ X=1.287, Y=-48.622 4. Direct Image A. exposure time=50 seconds. post flash=12 Pos Targ X=1.287, Y=-48.622 1 & 2 are at the same position, 3 & 4 are at the same position. These are paired to place the direct image in the same location as the dispersed images. The observability windows are dictated by V<17.86. This window opens on Jul 24 and closes on Aug 21 2018. The specific windows were determined by investigating when other bright and/or numerous objects would be in the field. 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 11351-LEUCU WFC3/UVI ACCUM G280-REF F300X FLASH=12 1 50 S (50 POS TARG null, -50; SEQ S S S) 1-2 NON-INT ------------------------------------------------------------------------------------------------------------------------------------ 2 11351-LEUCU WFC3/UVI ACCUM UVIS G280 CR-SPLIT=4 1 2114 S POS TARG null, -50 S S (2114 S) ------------------------------------------------------------------------------------------------------------------------------------ 3 11351-LEUCU WFC3/UVI ACCUM G280-REF F300X FLASH=12 1 50 S (50 POS TARG 1.287, -48.622; S S S) SEQ 3-4 NON-INT ------------------------------------------------------------------------------------------------------------------------------------ 4 11351-LEUCU WFC3/UVI ACCUM UVIS G280 CR-SPLIT=4 1 2114 S POS TARG 1.287, -48.622 S S (2114 S) ------------------------------------------------------------------------------------------------------------------------------------ 15259( 2) - 20-Jul-2017 21:05:53 - [ 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 | ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ 11351-LEUCUS 1 WFC3/UVI ACCUM G280-REF F300X none none none none 1 N/A S 11351-LEUCUS 2 WFC3/UVI ACCUM UVIS G280 none none none 1 1 N/A S 11351-LEUCUS 2 WFC3/UVI ACCUM UVIS G280 none none none 2 1 N/A S 11351-LEUCUS 2 WFC3/UVI ACCUM UVIS G280 none none none 3 1 N/A S 11351-LEUCUS 2 WFC3/UVI ACCUM UVIS G280 none none none 4 1 N/A S 11351-LEUCUS 3 WFC3/UVI ACCUM G280-REF F300X none none none none 2 N/A S 11351-LEUCUS 4 WFC3/UVI ACCUM UVIS G280 none none none 1 2 N/A S 11351-LEUCUS 4 WFC3/UVI ACCUM UVIS G280 none none none 2 2 N/A S 11351-LEUCUS 4 WFC3/UVI ACCUM UVIS G280 none none none 3 2 N/A S 11351-LEUCUS 4 WFC3/UVI ACCUM UVIS G280 none none none 4 2 N/A S 15259( 2) - 20-Jul-2017 21:05:53 - [ 8] Summary Form for Proposal 15259 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures G280-REF, UVIS ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFC3/UVIS ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters CR-SPLIT=2, CR-SPLIT=4, FLASH=12 ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements BETWEEN 01-MAR-2018:00:00:00 AND 02-MAR-2018:06:00:00, BETWEEN 02-AUG-2018:06:00:00 AND 02-AUG-2018:16:00:00, BETWEEN 03-MAR-2018:00:00:00 AND 05-MAR-2018:00:00:00, BETWEEN 04-FEB-2018:12:00:00 AND 11-FEB-2018:12:00:00, BETWEEN 07-AUG-2018:00:00:00 AND 08-AUG-2018:00:00:00, BETWEEN 08-AUG-2018:11:00:00 AND 08-AUG-2018:15:00:00, BETWEEN 09-MAR-2018:00:00:00 AND 11-MAR-2018:00:00:00, BETWEEN 11-AUG-2018:14:00:00 AND 13-AUG-2018:14:00:00, BETWEEN 12-MAR-2018:00:00:00 AND 13-MAR-2018:22:00:00, BETWEEN 14-FEB-2018:00:00:00 AND 19-FEB-2018:22:00:00, BETWEEN 15-MAR-2018:00:00:00 AND 23-MAR-2018:12:00:00, BETWEEN 17-AUG-2018:00:00:00 AND 17-AUG-2018:06:00:00, BETWEEN 18-AUG-2018:01:00:00 AND 19-AUG-2018:00:00:00, BETWEEN 19-AUG-2018:12:00:00 AND 19-AUG-2018:18:00:00, BETWEEN 20-AUG-2018:12:00:00 AND 21-AUG-2018:12:00:00, BETWEEN 21-FEB-2018:00:00:00 AND 26-FEB-2018:22:00:00, BETWEEN 24-MAR-2018:12:00:00 AND 27-MAR-2018:12:00:00, BETWEEN 29-MAR-2018:00:00:00 AND 30-MAR-2018:00:00:00, BETWEEN 31-JUL-2018:12:00:00 AND 01-AUG-2018:12:00:00, BETWEEN 31-MAR-2018:00:00:00 AND 08-APR-2018:00:00:00, POS TARG 1.287, -48.622, POS TARG null, -50, SEQ 1-2 NON-INT, SEQ 1-4 NON-INT, SEQ 3-4 NON-INT ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F300X, G280 ------------------------------------------------------------------------------------------------------------------------------------ Target Names 11351-LEUCUS, 617-PATROCLUS ------------------------------------------------------------------------------------------------------------------------------------