| DATA_SET_DESCRIPTION |
Data Set Overview
=================
This data set contains 94 asteroid spectra obtained by Scott
Sawyer as part of his Ph.D. dissertation at the University of
Texas at Austin.
Parameters
==========
Each spectrum is contained in a separate file, listing wavelength
and reflectance. The index file for this collection contains
observation dates, visual magnitude, integration time, phase
angle, solar elongation, geo- and heliocentric distances, airmass,
wavelength coverage limits, normalization wavelength and solar
analog stars for each spectrum included.
Processing
==========
The details of the data processing are reported in Sawyer (1991)
[SAWYER1991].
The spectra as shown in the figures of Sawyer (1991) have had the
noisy red and blue ends trimmed, and sections affected by telluric
H2O and O2 bands edited out. The versions of the spectra in this
archive have not had noisy ends and telluric bands edited out.
Comparison of these spectra with the figures in Sawyer (1991) will
show which sections were edited out for publication.
The spectra in Sawyer (1991) have been normalized to 1.0 at 0.57
microns if the spectrum covers that wavelength. Bluer spectra
are normalized at 0.45 microns, and redder spectra are normalized
at 0.80 microns. Several spectra in this archive do not follow
this pattern and the information is lacking to determine what
normalization and shifting have been applied to them. For these
spectra, the normalization wavelength is given as '9.99' in the
index file.
Modification History
====================
This data set first entered the PDS archives following its
successful external peer review on 23 March 1998.
This data set was re-examined as part of a general review of
holdings. At that time several upgrades and modification were
made. These included:
o Specific target names were inserted into all labels.
o The observational parameters in the 'sawindex.tab' file
were incorporated into the top-level description field
of the corresponding label.
o The date of observations from 'sawindex.tab' was inserted
into both the START_TIME and STOP_TIME fields of the
corresponding label.
o Data files were renamed to indicate the asteroid number
and name, with a sequence number only when multiple spectra
of a single object are present in this collection.
o It was determined that no spectrum file contained any
actual error values. The REFLECTANCE_ERROR column, formerly
present but filled with a flag value, was thus deleted from
all spectrum files and labels.
o Two files, '512herculina.tab' (formerly 'herculi1.tab') and
'5astraea1.tab' (formerly 'astrae1.tab') contained apparently
spurious data lines at the end of the spectrum. The
reflectance values in these lines were printed in a different
format from the rest of the file, and the values were 2-3
orders of magnitude smaller than the immediately preceding
spectral point. These lines have been deleted (2 lines from
'512herculina.tab' and 5 lines from '5astraea1.tab').
o The INSTRUMENT_HOST_NAME and INSTRUMENT_NAME fields,
previously marked 'N/A', have been filled with appropriate
values. In keeping with Small Bodies Node conventions for
ground-based spectra, the instrument host is considered to
be the telescope used; the instrument is the detector.
Catalog objects have been supplied for the two hosts and
two instruments newly defined.
o The 'sawindex.*' files were modified to reflect the new
file names.
o This catalog file was updated to include a complete list
of specific targets and to document the other changes.
|
| CONFIDENCE_LEVEL_NOTE |
Review
======
The data set underwent external peer review on March 23, 1998.
Limitations
===========
This data set is incomplete, in that only 94 of the 164 spectra
reported in Sawyer's thesis are included. The spectra included so
far were obtained by PDS from Faith Vilas, with the permission of
Scott Sawyer. PDS is currently attempting to locate a provider
for the remaining spectra. If they are obtained, they will be
added in an update of the data set.
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