PDS: Data Set Information

Data Set Information
DATA_SET_NAME	IRTF NEAR-IR SPECTROSCOPY OF ASTEROIDS V2.0
DATA_SET_ID	EAR-A-I0046-4-IRTFSPEC-V2.0
NSSDC_DATA_SET_ID
DATA_SET_TERSE_DESCRIPTION
DATA_SET_DESCRIPTION	Data Set Overview : All observations were obtained with SpeX, the low- to medium-resolution near-IR spectrograph and imager at the NASA Infrared Telescope Facility (IRTF) on Mauna Kea, Hawaii. This instrument uses prism cross-dispersers and gratings to achieve resolving powers up to R~2500 across the wavelength region from 0.8 to 5.5 microns. An infrared slit-viewer allows for object acquisition and guiding. The SpeX spectrograph employs a 1024x1024 Aladdin 3 InSb array and the slit-viewing imager uses a 512x512 Aladdin 2 InSb array. [RAYNERETAL2004]. Of specific importance to asteroid studies, SpeX provides a low-resolution (R~100 when using the nominal 0.8 arcsecond slit) 'prism' mode covering the wavelength interval 0.8-2.5 microns. In prism mode, asteroids as faint as Vmag~16.5 are routinely observed, with even fainter magnitude limits being reached when good sky conditions permit. Asteroid observations are normally obtained by taking nodded spectral image pairs of the target asteroid, solar-analog stars, and (possibly) telluric standard stars, followed by calibration flat-field and arc-lamp images. The image pairs are taken by shifting the asteroid (or star) position on the slit (nodding the telescope position) by a fixed amount. In this 'A-B' image pair, the background sky spectrum is being recorded simultaneously with the target, allowing the sky to be subtracted in both the A-B and B-A pairs. After flat fielding the individual SpeX images and carrying out the pairwise sky subtraction, multiple images of the target or standard star can be stacked, and a 1-dimensional spectrum extracted, wavelength calibrated and re-binned as appropriate. Calibration of each asteroid spectrum in dimensionless units of relative reflectance is achieved by dividing the asteroid spectrum by that of a solar analog star. Because this data set contains results derived by several different research groups, there are some variations in observing strategies and reduction procedures. This is particularly the case in the final stages of spectral calibration where effects of the Earth's atmosphere (telluric absorptions) are fitted and removed. Different techniques for telluric correction include: 1) the modeling of atmospheric absorption bands using ATRAN [LORD1992] which is based on the HITRAN database of molecular absorption lines (for convenience, a .pdf copy of Lord 1992, NASA Technical Memorandum 103957 is included in the document directory), 2) using the method included in SpeXTool [VACCAETAL2003] where observations of an A0 (telluric standard) star are convolved with a high-resolution model of Vega to construct a telluric correction spectrum, and 3) the use of SpecPR, where wavelength-dependent extinction coefficients are derived from nightly standard star observations. While the application of any of these telluric calibration methods leads to very similar results, users of this data set are encouraged to refer to the original papers for specific details about the data reduction and calibration procedures used. In the update to v2.0 of this data set, 225 spectra were added from 7 papers (identified with an '' in the list below). Papers for which data are archived are: Binzel et al. (2001) M&PS 36, 1167-1172 [BINZELETAL2001] Clark et al. (2004) AJ 128, 3070-3081 [CLARKETAL2004] Clark et al. (2009) Icarus 202, 119-133 [CLARKETAL2009B] Clark et al. (2010) JGR 115, E06005 [CLARKETAL2010]* Moskovitz et al. (2008) ApJ 682, L57-L60 [MOSKOVITZETAL2008B]* Moskovitz et al. (2010) Icarus 208, 773-788 [MOSKOVITZETAL2010]* Ockert-Bell et al. (2008) Icarus 195, 206-219 [OCKERT-BELLETAL2008]* Ockert-Bell et al. (2010) Icarus 210, 674-692 [OCKERT-BELLETAL2010]* Rivkin et al. (2005) Icarus 175, 175-180 [RIVKINETAL2005] Shepard et al. (2008) Icarus 193, 20-38 [SHEPARDETAL2008]* Sunshine et al. (2004) M&PS 39, 1343-1357 [SUNSHINEETAL2004] Sunshine et al. (2007) M&PS 42, 155-170 [SUNSHINEETAL2007B] Sunshine et al. (2008) Science 320, 514-517 [SUNSHINEETAL2008] Data File Description : Data file names have the format: AAAA_YYMMDDTHHMMSS.tab, where AAAA is the permanent number or provisional designation of the asteroid, YYMMDD is the UT start date, and HHMMSS the UT start time of the observation. This naming convention is particularly useful when a study involved rotationally resolved spectra, where multiple spectral files are being archived for a single asteroid. To determine what asteroid spectra have been archived, and to help navigate to specific files, a science index (science_index.tab) is included in the index directory. This file lists all spectra in order of asteroid designation, and includes the data path, UT start and end times of the first and last asteroid observations used in creating the spectrum, the apparent magnitude, phase angle and heliocentric distance of the asteroid at the time(s) of the observations(s), and a listing of the solar analog stars used in calibration. Each spectrum file contains 3 columns: wavelength (in microns), relative reflectance, and error in relative reflectance. For those spectra reduced using IRAF, the output spectrum is usually re-binned to a consistent dispersion, which allows different spectra to be easily compared and combined. During the various reduction and calibration steps, if a particular spectral data point is identified as discrepant, that point is flagged and removed from the final spectrum file. All spectra have been scaled by fitting a polynomial over the region centered on the J-band (1.215 microns), and then normalizing the fitted value at 1.215 microns to 1.00. Thumbnail plots of all spectra archived in this data set are provided (pdf files) in the document directory. These plots are organized by publication (one file per publication), using the same naming scheme as the data directory structure.
DATA_SET_RELEASE_DATE	2011-05-31T00:00:00.000Z
START_TIME	2000-09-04T02:46:35.000Z
STOP_TIME	2009-08-01T02:39:19.000Z
MISSION_NAME	SUPPORT ARCHIVES
MISSION_START_DATE	2004-03-22T12:00:00.000Z
MISSION_STOP_DATE	N/A (ongoing)
TARGET_NAME	1014 SEMPHYRA 1020 ARCADIA 1039 SONNEBERGA 1098 HAKONE 110 LYDIA 1103 SEQUOIA 112 IPHIGENIA 1228 SCABIOSA 1251 HEDERA 1275 CIMBRIA 129 ANTIGONE 1317 SILVRETTA 135 HERTHA 136 AUSTRIA 143 ADRIA 144 VIBILIA 1468 ZOMBA 1545 THERNOE 1580 BETULIA 16 PSYCHE 166 RHODOPE 1662 HOFFMANN 17 THETIS 173 INO 179 KLYTAEMNESTRA 1858 LOBACHEVSKIJ 186 CELUTA 1903 ADZHIMUSHKAJ 1929 KOLLAA 2 PALLAS 2042 SITARSKI 2045 PEKING 2048 DWORNIK 209 DIDO 21 LUTETIA 2100 RA-SHALOM 213 LILAEA 214 ASCHERA 216 KLEOPATRA 217 EUDORA 221 EOS 224 OCEANA 229 ADELINDA 233 ASTEROPE 234 BARBARA 2371 DIMITROV 2401 AEHLITA 2442 CORBETT 246 ASPORINA 250 BETTINA 2501 LOHJA 2504 GAVIOLA 2511 PATTERSON 25143 ITOKAWA 2566 KIRGHIZIA 2579 SPARTACUS 260 HUBERTA 2606 ODESSA 2653 PRINCIPIA 27343 DEANNASHEA 2763 JEANS 2795 LEPAGE 2823 VAN DER LAAN 283 EMMA 284 AMALIA 2851 HARBIN 289 NENETTA 2912 LAPALMA 304 OLGA 3103 EGER 3155 LEE 317 ROXANE 322 PHAEO 335 ROBERTA 3363 BOWEN 337 DEVOSA 3395 JITKA 347 PARIANA 354 ELEONORA 359 GEORGIA 3657 ERMOLOVA 3703 VOLKONSKAYA 375 URSULA 3782 CELLE 379 HUENNA 38070 REDWINE 3819 ROBINSON 383 JANINA 387 AQUITANIA 397 VIENNA 4 VESTA 4038 KRISTINA 409 ASPASIA 41 DAPHNE 417 SUEVIA 4188 KITEZH 419 AURELIA 4215 KAMO 426 HIPPO 43 ARIADNE 434 HUNGARIA 44 NYSA 441 BATHILDE 4426 ROERICH 446 AETERNITAS 46 HESTIA 4796 LEWIS 497 IVA 50 VIRGINIA 505 CAVA 5111 JACLIFF 517 EDITH 53 KALYPSO 536 MERAPI 547 PRAXEDIS 5481 KIUCHI 5498 GUSTAFSSON 55 PANDORA 559 NANON 572 REBEKKA 5840 RAYBROWN 599 LUISA 62 ERATO 64 ANGELINA 661 CLOELIA 676 MELITTA 678 FREDEGUNDIS 679 PAX 686 GERSUIND 709 FRINGILLA 71 NIOBE 712 BOLIVIANA 739 MANDEVILLE 742 EDISONA 75 EURYDIKE 757 PORTLANDIA 758 MANCUNIA 768 STRUVEANA 77 FRIGGA 771 LIBERA 779 NINA 7800 ZHONGKEYUAN 785 ZWETANA 789 LENA 808 MERXIA 809 LUNDIA 844 LEONTINA 847 AGNIA 863 BENKOELA 87 SYLVIA 872 HOLDA 89 JULIA 899 JOKASTE 909 ULLA 9481 MENCHU 9553 COLAS 956 ELISA 97 KLOTHO 973 ARALIA 976 BENJAMINA 980 ANACOSTIA 984 GRETIA 99 DIKE ASTEROID ASTEROID 10537 ASTEROID 139359 ASTEROID 16416 ASTEROID 26760 ASTEROID 26886 ASTEROID 29075 ASTEROID 33881 ASTEROID 36412 ASTEROID 50098 ASTEROID 97276
TARGET_TYPE	ASTEROID
INSTRUMENT_HOST_ID	OBS376T3
INSTRUMENT_NAME	SPEX
INSTRUMENT_ID	I0046
INSTRUMENT_TYPE	SPECTROMETER
NODE_NAME	Small Bodies
ARCHIVE_STATUS	LOCALLY_ARCHIVED
CONFIDENCE_LEVEL_NOTE	Confidence Level Overview : The uncertainty for each spectral channel has been derived using Poisson statistics, and was based on the signal from both the object and sky, as well as the detector characteristics. The errors listed in each spectral file do not include systematic uncertainties. Examples of such systematics include uncertainties in the telluric absorption correction model, and uncertainties in the telescopic observations that can affect the average slope as measured over the length of the spectrum. By measuring several calibration stars over the course of a night and averaging the results from each asteroid / star combination, the level of systematic errors in the final asteroid spectra have been minimized.
CITATION_DESCRIPTION	Bus, S. J., Ed., IRTF Near-IR Spectroscopy of Asteroids V2.0. EAR-A-I0046-4-IRTFSPEC-V2.0. NASA Planetary Data System, 2011.
ABSTRACT_TEXT	This data set contains low-resolution, near-infrared (0.8 - 2.5 micron) spectra of asteroids obtained with SpeX at the NASA Infrared Telescope Facility (IRTF) on Mauna Kea. Since it was commissioned in June 2000, SpeX has been the premier instrument for producing high quality near-IR spectra of asteroids. These spectra have been used for both taxonomic studies of asteroids, and for more detailed mineralogical and compositional investigations. This data set archives the reduced, calibrated spectra that have been published in the peer-reviewed literature, and will be regularly updated as more data become publicly available.
PRODUCER_FULL_NAME	SCHELTE BUS
SEARCH/ACCESS DATA	SBN PSI WEBSITE

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