8578( 7) - 02/25/04 15:13 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 8578 Version: 7 Check-in Date: 25-Feb-2004 15:12:07 1.Proposal Title: First Spectroscopy of an Asteroid and its Satellite: (45) Eugenia and S/1998 (45) 1 ------------------------------------------------------------------------------------ 2. Proposal For 3. Cycle GO 9 ------------------------------------------------------------------------------------ 4. Investigators Contact? PI: Dr. William J. Merline Southwest Research Institute CoI: Dr. Clark R. Chapman Southwest Research Institute N CoI: Dr. Laird Close European Southern Observatory - Germany N CoI: Dr. Christophe Dumas Jet Propulsion Laboratory N CoI: Dr. S. Alan Stern Southwest Research Institute N CoI: Dr. Schelte J. Bus Massachusetts Institute of Technology N CoI: Dr. Richard P. Binzel Massachusetts Institute of Technology N ------------------------------------------------------------------------------------ 5. Abstract We recently made the first-ever discovery of a satellite of an asteroid from the Earth, using adaptive optics (Merline et al. 1999a, 1999b). We propose here to acquire the first separate, comparative, and simultaneous spectra of an asteroid and its satellite. We will employ the UV-capabilities and high-spatial-resolution properties of STIS to study (45)Eugenia, and its satellite, S/1998(45)1, by obtaining medium-resolution spectra over the range 2900-10300 Angstrom, using only two grating settings, on a single HST orbit. We will determine whether the spectra, and hence surface compositions, are similar or different in a parent-satellite pair, and to test hypotheses concerning satellite production mechanisms. From the orbital parameters, determined using our ground-based adaptive-optics images, we have already determined that (45)Eugenia has a surprisingly low density of 1.2 g cm^-3. We know the spectrum of Eugenia is a (Tholen) FC-type, which is similar to the common C-types, but differs by the lack of a UV-band or UV-dropoff and by subtle, but measurable differences in the spectral slope. Both the UV-region and the existence of subtle absorption features in the near-IR (~ 0.9 micron) are diagnostic of the specific differences between F-, C-, and (Bus') X-class. HST spectroscopy is the only way to separate the pair, because ground-based adaptive optics is not available in the UV and cannot yet provide adequate resolution in the visible. ------------------------------------------------------------------------------------ 8578( 7) - 02/25/04 15:13 - [ 2] Observations Description ------------------------ Standard aquisition images of 1s prior to incorporating the 52x2 slit for spectroscopic observations. Gratings 430L and 750L at prime tilts each at two dither-along-slit exposure pairs. Binning by 4 in dispersion axis only. Fringe flat for 750L exposures. Orient angle of 100 degrees is selected as near nominal roll angle in March 2004. Timing, as expressed through phase, is such that target primary and satellite are both along slit at orient angle 100 degrees (sky position angle of 55 degrees) or 180 degree flip. Real Time Justification ----------------------- Calibration Justification ------------------------- Fringe flat for 750L. Spectral features of interest have comparable scale to fringes, so they must be measured per standard procedures for such data. Additional Comments ------------------- Soonest opportunity preferred to maximize projected separation and brightness of this receeding target. ------------------------------------------------------------------------------------ 8578( 7) - 02/25/04 15:13 - [ 3] TARGET LIST Solar System Targets ------------------------------------------------------------------------------------------------------------------------------------ TARGET NUMBER: 1 | TARGET NAME: ASTEROID-45 ------------------------------------------------------------------------------------------------------------------------------------ TARGET DESCRIPTION: ASTEROID Eugenia ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 1 | TARGET POSITION LEVEL 2 | TYPE=ASTEROID,A=2.7202531,E=0.0831485,I= | 6.61223,O=147.9608,W=85.67345,M=251.0385 | ,EPOCH=27-Dec-2003,EQUINOX=J2000 | | ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 3 | WINDOWS | | ------------------------------------------------------------------------------------------------------------------------------------ DATA | COMMENTS | V = 12.1+/-0.2 | satellite is 6 mag fainter | | ------------------------------------------------------------------------------------------------------------------------------------ 8578( 7) - 02/25/04 15:13 - [ 4] Patterns ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 1 Primary_Pattern Secondary_Pattern Pattern_Type STIS-ALONG-SLIT Pattern_Purpose DITHER Number_Of_Points 2 Point_Spacing 0.9385 Coordinate_Frame POS-TARG Pattern_Orient 90.0 Center_Pattern NO ------------------------------------------------------------------------------------------------------------------------------------ 8578( 7) - 02/25/04 15:13 - [ 5] Visit: 01 Visit Priority: Visit Requirements: PCS MODE FINE; GUID TOL 0.5"; ORIENT 98.0D TO 102.0 D; BEFORE 01-APR- 2004:00:00:00; Period 56.505 H AND ZERO-PHASE JD2453076.45833 On Hold Comments: Additional Comments: Timing of this visit is such that satellite and primary separation axis is within 20 degrees of STIS slit. Real period of system is 4.708days, but 180 degree symmetry, so every 2.354days is a visit allowable time. Phased so that exposure level phase is 0.5 +- 0.106. Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 ASTEROID-45 STIS/C ACQ F28X50L MIRROR ACQTYPE=POINT 1 1 S PHASE 0.3938 TO 0.6062 CD P ------------------------------------------------------------------------------------------------------------------------------------ 2 ASTEROID-45 STIS/C ACCUM 52X2 G430L 4300 GAIN=4,CR-SPLIT=2,BINAXIS2=1, 1 340 S PATTERN 1 2 CD BINAXIS1=4 ------------------------------------------------------------------------------------------------------------------------------------ 3 ASTEROID-45 STIS/C ACCUM 52X2 G750L 7751 GAIN=4,CR-SPLIT=2,BINAXIS2=1, 1 500 S PATTERN 1 3 CD BINAXIS1=4 ------------------------------------------------------------------------------------------------------------------------------------ 4 CCDFLAT STIS/C ACCUM 52X2 G750L 7751 BINAXIS2=1,BINAXIS1=4 2 DEF CD ------------------------------------------------------------------------------------------------------------------------------------ Sub Exposures ------------------------------------------------------------------------------------------------------------------------------------ Visit Id| Exp Id |Primary |Secondary |Iteration |CR-SPLIT |Orbit Num |Duration | |Pattern Pos |Pattern Pos |Num |Num | | ------------------------------------------------------------------------------------------------------------------------------------ 01 1 none none none none 1 tbd 01 2 1 none none 1 1 tbd 01 2 1 none none 2 1 tbd 01 2 2 none none 1 1 tbd 01 2 2 none none 2 1 tbd 01 3 1 none none 1 1 tbd 01 3 1 none none 2 1 tbd 01 3 2 none none 1 1 tbd 01 3 2 none none 2 1 tbd 01 4 none none 1 none 1 tbd 01 4 none none 2 none 1 tbd 8578( 7) - 02/25/04 15:13 - [ 6] Summary Form for Proposal 8578 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures F28X50LP 52X2 ------------------------------------------------------------------------------------------------------------------------------------ Configurations STIS/CCD ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters ACQTYPE=POINT BINAXIS1=4 BINAXIS2=1 ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements PCS MODE FINE; GUID TOL 0.5"; ORIENT 98.0D TO 102.0 D; BEFORE 01-APR-2004 00 00 00; Period 56.505 H AND ZERO-PHASE JD2453076.45833 PHASE 0.3938 TO 0.6062 PATTERN 1 2 PATTERN 1 3 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements MIRROR G430L G750L ------------------------------------------------------------------------------------------------------------------------------------ Target Names ASTEROID-45 CCDFLAT ------------------------------------------------------------------------------------------------------------------------------------ Wavelengths 4300 7751 ------------------------------------------------------------------------------------------------------------------------------------