| DATA_SET_DESCRIPTION |
Data Set Overview
================
All observations were obtained at the Michigan-Dartmouth-MIT (MDM)
Observatory on the southwest ridge of Kitt Peak in Arizona. The
majority of observations were made with the 2.4 m Hiltner telescope,
with the remainder being made with the 1.3 m McGraw-Hill telescope.
The Mark III spectrograph was used throughout the SMASSII survey and
was equipped with either a SITE 1024 x 1024 thinned, backside
illuminated CCD (with 24-micron pixels), or a Loral 2048 x 2048
thick, front-side illuminated CCD (with 15-micron pixels). The
spectrograph was used with a low-resolution grism (150 lines per mm,
blazed at 0.73 micron), giving a dispersion of roughly 0.001 micron
per pixel. A 4.5-arcsec wide slit, oriented in the north-south
direction on the sky, was used for all observations, giving a
spectral resolution of about 0.007 micron (R ~ 100). To block the
second-order spectrum that would otherwise have been superimposed on
the first-order spectrum, a Wratten 22 filter was always placed over
the long-wavelength half of the CCD dewar window. This arrangement
allowed for the entire first-order spectrum, covering the wavelength
range from 0.4 to 1.0 micron, to be recorded in a single exposure.
All data reduction and calibration was carried out using tasks in
the Image Reduction and Analysis Facility (IRAF), developed and
maintained by NOAO. Upon extraction of the 1-D spectra from the CCD
images, the spectra were rebinned to a consistent dispersion of
0.0025 micron, allowing different spectra to be easily compared and
combined. A correction for atmospheric extinction was applied to
the data using the airmass of each observation and a mean extinction
model developed for Kitt Peak (based on Hayes and Latham, A.J. 197
593-601, 1975). Calibration of each asteroid spectrum in units of
relative reflectance was achieved using one of four solar analog
stars: 16CygB (HD186427), Hyades64 (HD28099), HR4486 (HD101177), and
HR5384 (HD126053).
A total of 1341 spectra are included in the SMASSII survey. The
data have been published in Bus and Binzel (Icarus 158, 106-145,
2002) [BUS&BINZEL2002]. Details about the observations and data
reduction procedures can be found therein.
Data File Description
================
Each spectrum presented here contains up to 197 relative reflectance
measurements over the spectral interval from 0.435 to 0.925 micron
with a step size of 0.0025 micron. Files may contain fewer that 197
points when specific spectral channels were rejected, usually due to
poor cancellation of telluric bands. All spectra have been scaled
by fitting a polynomial over the region centered on 0.55 micron, and
then normalizing the fitted value at 0.55 micron to 1.00.
Column 1 -
Sampling Parameter Name: WAVELENGTH
Sampling Parameter Unit: MICROMETER
Minimum Sampling Parameter: 0.435
Maximum Sampling Parameter: 0.925
Column 2 -
Data Parameter Name: RELATIVE REFLECTANCE
Data Parameter Unit: DIMENSIONLESS
Column 3 -
Data Uncertainty Name: RELATIVE REFLECTANCE ERROR
Data Uncertainty Unit: DIMENSIONLESS
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| CONFIDENCE_LEVEL_NOTE |
Confidence Level Overview
=========================
The uncertainty for each spectral channel was derived using Poisson
statistics, and was based on the signal from both the object and
sky, as well as the detector characteristics. These errors do not
include systematic uncertainties that, in particular, can affect the
average slope as measured over the length of the spectrum. A more
complete discussion of the confidence level for these data, and the
potential contribution of systematic effects is given in Bus and
Binzel 2002 [BUS&BINZEL2002].
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