| DATA_SET_DESCRIPTION |
Data Set Overview
=================
This data set contains 52-color IR spectra taken using a double
circularly variable filter. The short wavelength portion of the
CVF covered the octave from 0.8 to 1.6 microns with 3 percent
resolution, while the long wavelength portion covered 1.5 to 2.6
microns with 5 percent resolution. There is some overlap in the
spectral coverage between 1.5 and 1.6 microns, which is evident as
a discontinuity in the wavelengths after the first 32 values,
which were obtained with the short wavelength portion, while the
remaining 20 values were obtained with the long wavelength
portion.
Errors were computed from the standard deviation of the multiple
scans through the CVF. If only one scan was performed, the error
is left blank. Note that due to the small number of scans, the
errors are often both underestimated and overestimated.
Some wavelength positions correspond to telluric features and were
intentionally blanked. In other cases, especially near the ends
of the CVF, the data were either not taken or were hopelessly
noisy, so those entries were also blanked.
The following code letters are used for the various solar analog
stars:
A = 18 Aquarii
B = 16 Cygni B
O = 13 Orionis
V = 70 Virginis
The observation date for 113 Amalthea is given as 054/05/85 in the
original machine readable data file. The assumption has been made
that the 4 is a typographical error, based on the fact that other
observations were made on 05/05/85.
Not all dates of observation are available. In particular, those
asteroid observations contributed by R.H. Brown did not include
observation dates in the original machine readable data file.
One observation was taken from the literature, namely Cruikshank
and Hartmann (1984) [CRUIKSHANK&HARTM1984].
Reference: Cruikshank, D.P., and W.K. Hartmann 1984. The
meteorite- asteroid connection: Two olivine-rich asteroids.
Science 223, 281-283. [CRUIKSHANK&HARTM1984]
Parameters
==========
The data tables have one entry for each observation, with fields
for the following parameters: asteroid catalog number; a code for
the solar analog star used with that observation; the date of
observation; and reflectances and error values for each of 52
bandpasses.
Data
====
The reflectances in each of the 52 bands are given in the table
'52color.tab'. The errors are given in the table '52error.tab'.
The asteroid identification, solar analog code, and observation
date are provided in each of these two files.
Ancillary Data
==============
The ancillary file '52waves.tab' presents the effective
wavelengths of each of the 52 positions of the CVF which were used
for the survey, arranged in a single record with a separate field
for each wavelength. The file '52waves2.tab' gives the same
information arranged with one wavelength per record. Each record
also contains the FWHM of the bandpass.
Media/Format
============
This dataset is released in the form of ASCII files which may be
stored on disk or other magnetic medium and which may be
distributed by ftp, email, real-time access by remote login, or by
whatever means is most convenient.
Modification History
====================
As part of a general review of asteroid holdings in February 2002,
these data were examined and the existing labels edited slightly.
In addition, a new format for the spectra was also provided.
Changes made at that time include:
o Existing labels were edited to update version numbers, remove
redundant descriptions, and add MISSING_CONSTANT and
SCALING_FACTOR keywords, where appropriate.
o The three separate columns previously defined for the year,
month and day of observation in the 52color.tab and
52error.tab file labels were combined into a single column
with a data type of DATE. Column numbers throughout these
labels were updated accordingly.
o The 52color.tab, 52error.tab and 52waves2.tab files were used
to create separate, complete spectrum files for each line in
the original records. Each spectrum record lists bandpass,
FWHM, reflectance and error in each of the 52 filters.
o In the newly created spectrum files, the values were resorted
so that wavelengths are strictly increasing. Thus, the overlap
described above which shows up in the original data files as a
discontinuity in wavelength is not apparent in the individual
spectrum files. This was done to facilitate plotting the
spectra.
o Names were extracted from the Small Bodies Data Base and used
to identify the specific targets and name the individual
spectrum files.
o This data set catalog file was itself updated to document
changes and the explicit target name list.
No data values were changed, nor were the formats of the existing
data files altered.
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