| DATA_SET_DESCRIPTION |
Data Set Overview
=================
This dataset is comprised of asteroid flux data measured in 26
filters using the McCord dual beam photometer. Of the 26 filters
used for the full dataset, a maximum of 24 were used for any one
measurement. The wavelength range covered is from 0.32 to 1.08
micrometers.
Processing Level Id : 3
Software Flag : N
Processing Start Time : 1975
Processing Stop Time : 1984
Parameters
==========
Sampling Parameter Name : WAVELENGTH
Data Set Parameter Name : FLUX RATIO
Minimum Sampling Parameter : 0.330000
Maximum Sampling Parameter : 1.100000
Data Set Parameter Unit : DIMENSIONLESS
Noise Level : 2.000000
Sampling Parameter Unit : MICROMETER
Data
====
FLUX RATIO is defined as the ratio of two measured photon fluxes
from a photometric or spectrometric instrument. For instance, the
ratio of the measured spectrum of a target relative to the
measured spectrum of a calibration standard will yield a value
that is a flux ratio. This parameter is dimensionless.
Ancillary Data
==============
Atmospheric Conditions
----------------------
An estimate of the quality of the observing conditions for each
night of observing is given in the original papers, Chapman
(1972) [CHAPMAN1972], Chapman and Gaffey (1979)
[CHAPMAN&GAFFEY1979A] [CHAPMAN&GAFFEY1979B] and McFadden et al.
(1984) [MCFADDENETAL1984].
Calibration Standard
--------------------
The data are calibrated to flux ratio (asteroid/inferred sun)
with reference to a set of standard stars. During the
observation sessions, the standard stars are observed both to
determine extinction corrections in each filter and as color
standards. Many of the standard stars used are A- or B-
Oke/Hayes standard stars and others of the solar type.
Modification History
====================
As part of a general review and upgrade of current asteroid
data sets, these data were reviewed and an additional format
added. The following changes were made to existing files:
o The 24color.lbl file was edited slightly for grammar and
to add the internal PDS reference keys corresponding to
the cited references.
o The asteroid number corresponding to object 1980 AA was
added to the 24color.tab file.
In addition, a program was written and used to split the
24color.tab file into separate spectrum files for each
observation, each with its own label file. These files are
named by the number and name of the corresponding asteroid.
The first two columns of each spectrum file indicate the
specific filter wavelength and FWHM used; these are followed
by the reflectance and uncertainty.
Only one object, 1685 Toro, had two observations in the main
data file. These are in separate files: '1685toro1' contains
the data from Chapman & Gaffey (1979b); '1685toro2' contains
the data from McFadden, et al. (1984).
Asteroid 1865 Cerberus, which had no data recorded in the
original file, has no individual spectrum file.
No changes were made to the recorded data values.
|
| CONFIDENCE_LEVEL_NOTE |
Confidence Level Overview
=========================
Acquisition of the 24 data points takes time; thus, a 24-point
spectrum can be affected by the varying light curve of the
asteroid, as well as by the changing sky conditions and instrument
stability. In most, but not all, cases, data were co-added from
numerous rapid rotations of the filter wheel. Uncertainties in
the relative calibration between stars and Alpha Lyrae may
contribute an uncertainty of up to 2 0n the visible and 4 0n the
infrared bands. It is believed that this uncertainty is larger
than other systematic errors in the data.
|
.png)
.png)
