Data Set Information
DATA_SET_NAME HARDERSEN IRTF ASTEROID NIR REFLECTANCE SPECTRA V1.0
DATA_SET_ID EAR-A-I0046-3-HARDERSENSPEC-V1.0
NSSDC_DATA_SET_ID
DATA_SET_TERSE_DESCRIPTION
DATA_SET_DESCRIPTION Data Set Overview : This dataset contains average Near-Infrared (NIR) reflectance spectra for 68 main-belt asteroids that were observed at the NASA Infrared Telescope Facility (IRTF) from April 2001 to May 2015. These asteroids were used as a part of three research investigations to better constrain their NIR spectra, assigned taxonomies, surface mineralogies, and potential meteorite analogs. The asteroids in this dataset were all observed in a very similar manner across the entire dataset. The resulting average NIR asteroid spectra in this dataset were also reduced in a very similar manner using two different software packages. The research projects that utilized these average NIR spectra include: 1) an investigation of the spectral and mineralogical diversity of the M-/X-type asteroids (Hardersen et al., 2005, 2011), 2) a study to better define the basaltic asteroid population in the main asteroid belt (Hardersen et al., 2014, 2015, 2016), and 3) an investigation of (1459) Magnya and its spectral and mineralogical comparison to (4) Vesta (Hardersen et al., 2004). Hardersen et al. (2005) reported the first results of the M-/X-type asteroid study, which included six M-type asteroids, while Hardersen et al. (2011) provided the final results of this effort that included NIR reflectance spectra for 45 M-/X-type asteroids. These works reported on the identification of significant NIR spectral and surface mineralogical diversity among this group of asteroids, the widespread detection of weak mafic silicate absorption features for pyroxene and olivine (1-5% band depths), detections of possible phyllosilicate features on a few asteroids, and widely varying NIR spectral slopes across the entire spectral dataset. Hardersen et al. (2014, 2015) were the first results of an effort to better constrain the basaltic asteroid population throughout the main asteroid belt. This is being accomplished by obtaining NIR spectra of Carvano et al. (2010) classified Vp-type asteroids with Wide-Field Infrared Survey (WISE)-derived albedos consistent with basalt (Masiero et al., 2011) from a dataset compiled by Mainzer et al. (2012). All of the average asteroid NIR reflectance spectra in this dataset were observed at the NASA Infrared Telescope Facility (IRTF), Mauna Kea, Hawaii. The asteroids reported in Hardersen et al. (2004, 2005, 2011, 2014) used the first-generation of the SpeX 0.7-5.3 micron spectrograph while the results in Hardersen et al. (2015) and the expected publication of Hardersen et al. (2016) used the second-generation of the SpeX spectrograph. All observations used the low-resolution, prism mode of the SpeX spectrograph (R : 94), the 0.8 arc second slit, an open dichroic, and an open order sorter filter. Most observations taken prior to 2008 were not observed at the parallactic angle while all observations after 2008 were observed at the parallactic angle. The vast majority of the observations that resulted in this dataset were made in clear to mostly clear weather conditions at the summit of Mauna Kea. All observations were conducted in a uniform manner. For each asteroid, an associated extinction star (late F- to late G-type main sequence) was observed close to the asteroid on the sky (less than 5 degrees separation). Stellar observations were interspersed with asteroid observations to ensure that the extinction star airmass range exceeded that of the associated asteroid. The extinction star observations are necessary for later removal of the NIR telluric absorptions during data reduction. One well-known solar analog (SAO 31899, SAO 93936, or SAO 120107) was observed each night, which was used in the reduction process to correct for the use of non-G2V extinction stars and to implement a slope correction so the final asteroid spectrum would mimic that if the actual reflected light from the Sun had been used. Data reduction for the asteroids used either SpecPR (Clark, 1980; Gaffey, 2003) or Spextool (Cushing et al., 2004). For those asteroids reduced using SpecPR, the sky background signal removal was accomplished using the Image Reduction and Analysis Facility (IRAF), followed by importing the sky-subtracted data into SpecPR. SpecPR routines included derivation of the 1st-order extinction coefficients from the extinction stars as a function of wavelength and airmass for up to five sets of extinction star observations (10 spectra per set), sub-channel pixel offsets for alignment of multiple spectra, and averaging routines. Spextool routines include a sky signal subtraction routine and a telluric correction that utilizes two sets of extinction star observations while also including the sub-channel pixel shifting and averaging routines. Wavelength calibration for SpecPR data is conducted manually by matching argon calibration emission lines/wavelengths to discrete channels and applying a polynomial function to convert the NIR spectra from channels to wavelengths. Spextool implements an internal wavelength calibration using one set of argon calibration spectra. For all data, each final average asteroid NIR spectrum can be qualitatively summarized as follows: (Asteroid/Sun) : (Asteroid/Extinction Star) / (Solar Analog Star/Extinction Star), where (Asteroid/Sun) represent the final average asteroid NIR spectrum, (Asteroid/Extinction Star) represents an intermediate average asteroid NIR spectrum after telluric and channeling shifting corrections, and (Solar Analog Star/Extinction Star) is the average stellar spectrum used to correct for observations of non-G2V extinction stars. The average (Solar Analog Star/Extinction Star) spectrum is smoothed to remove telluric absorptions as broad absorption features are not expected in stellar spectra and observations of solar analog stars are typically in very divergent parts of the sky during most IRTF observing runs. The data products in this dataset include the average NIR reflectance spectrum for each of the 68 asteroids. Each asteroid has its own text file that includes two or three columns of data that include wavelength, normalized reflectance, and error values. Most of the SpecPR-derived NIR spectra lack errors in the associated files while most of the Spextool data include errors. Where errors are reported, they are standard errors in SpecPR, or standard errors Robust Weighted Mean in Spextool. Spextool data are normalized at 1.5 microns while SpecPR data are normalized near 1.7 microns. The reported errors for the asteroid spectra that were reduced using Spextool are only the formal errors produced by the Spextool software. The reported errors result from the average of each individual asteroid spectrum, using the error method chosen in Spextool, where each individual asteroid spectrum is divided by the associated extinction star spectrum. The fully propagated errors are not reported, but will be reported in future updates to this dataset. The reported errors for the asteroid spectra reduced using SpecPR are fractions based on the variability of the point-to-point data scatter present in each final average asteroid spectrum reported here. Typical errors across a spectrum for most of the asteroids range from 1-3% with some asteroids having larger errors in spectral regions containing poorly-corrected telluric features and at longer wavelengths where SpeX has reduced sensitivity.
DATA_SET_RELEASE_DATE 2016-06-02T00:00:00.000Z
START_TIME 2001-04-29T06:00:00.000Z
STOP_TIME 2015-01-19T01:30:00.000Z
MISSION_NAME SUPPORT ARCHIVES
MISSION_START_DATE 1965-01-01T12:00:00.000Z
MISSION_STOP_DATE 2015-01-01T12:00:00.000Z
TARGET_NAME 785 ZWETANA
ASTEROID 19165
796 SARITA
10666 FELDBERG
413 EDBURGA
69 HESPERIA
418 ALEMANNIA
9553 COLAS
224 OCEANA
5560 AMYTIS
ASTEROID 30872
497 IVA
1461 JEAN-JACQUES
766 MOGUNTIA
758 MANCUNIA
ASTEROID 5754
ASTEROID 29796
110 LYDIA
250 BETTINA
2011 VETERANIYA
441 BATHILDE
5875 KUGA
504 CORA
872 HOLDA
338 BUDROSA
3849 INCIDENTIA
931 WHITTEMORA
8149 RUFF
347 PARIANA
201 PENELOPE
860 URSINA
6976 KANATSU
382 DODONA
9147 KOURAKUEN
857 GLASENAPPIA
21 LUTETIA
3782 CELLE
3715 STOHL
184 DEJOPEJA
1459 MAGNYA
739 MANDEVILLE
ASTEROID 15237
558 CARMEN
132 AETHRA
125 LIBERATRIX
516 AMHERSTIA
325 HEIDELBERGA
31414 ROTARYSUSA
1210 MOROSOVIA
55 PANDORA
ASTEROID
77 FRIGGA
ASTEROID 32940
417 SUEVIA
ASTEROID 17469
369 AERIA
22 KALLIOPE
16 PSYCHE
71 NIOBE
216 KLEOPATRA
129 ANTIGONE
97 KLOTHO
2168 SWOPE
798 RUTH
5235 JEAN-LOUP
3867 SHIRETOKO
ASTEROID 6331
136 AUSTRIA
135 HERTHA
TARGET_TYPE ASTEROID
INSTRUMENT_HOST_ID OBS376T3
INSTRUMENT_NAME SPEX
INSTRUMENT_ID I0046
INSTRUMENT_TYPE IMAGER
SPECTROMETER
NODE_NAME Small Bodies
ARCHIVE_STATUS LOCALLY ARCHIVED
CONFIDENCE_LEVEL_NOTE Confidence Level Overview : Most observations at the NASA IRTF were in clear, photometric conditions, but there were a few instances of cirrus present in the sky.
CITATION_DESCRIPTION Hardersen,P.S., Hardersen IRTF Asteroid NIR Reflectance Spectra V1.0. EAR-A-I0046-3-HARDERSENSPEC-V1.0. NASA Planetary Data System, 2016.
ABSTRACT_TEXT This dataset includes average near-infrared (NIR) reflectance spectra for 68 main-belt asteroids that were observed at the NASA Infrared Telescope Facility (IRTF), Mauna Kea, Hawaii, from April 2001 to January 2015. Raw NIR spectral data were obtained under mostly uniform instrumental conditions and include observations of the asteroids, extinction stars, and solar analog stars that were necessary for data reduction and production of the final average asteroid NIR reflectance spectra. SpecPR and Spextool were used during data reduction to produce the final spectra and both programs utilize similar functions that include sky background subtraction, telluric corrections, channel shifting, and averaging routines. The set of asteroids observed include a wide variety of taxonomic types and include V-, S-, M-, X-types that correspond to a wide variety of surface mineralogies, rock types, and potential meteorite analogs.
PRODUCER_FULL_NAME PAUL HARDERSEN
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