The MIT-UH-IRTF Joint Campaign
for NEO Spectral Reconnaissance
Data format, data rejection, and data normalization notes
Filenames are in the format:
- aNNNNNN, where NNNNNN is the asteroid number.
- auYYYYPD, where YYYYPD is the provisional designation, if unnumbered.
Files are space delimited, with four columns.
- Column 1: Wavelength in microns
- Column 2: Normalized reflectance.
Normalization is at 0.55 micron, when visible wavelength
data are available.
Otherwise, normalization is made near 1.21 microns
(weighted average over 1.16 to 1.26 microns).
This value is set to −1 in the case of a rejected
datum. Rejected data values should not be plotted
or used in any model fitting of the spectrum.
- Column 3: One-sigma uncertainty for the reflectance value.
This value is set to −1 in the case of a rejected datum.
- Column 4: Number of individual reduced Spex images averaged
together to produce the final reflectance value at this wavelength.
The column 4 entry is equal to "0" in the case of a rejected datum.
For visible wavelength SMASS data, this value is arbitrarily
set equal to "1" (as the number of averaged points is not
maintained in the SMASS archive).
When available, visible wavelength data from the
SMASS survey are
included. The SMASS data are listed first, followed by a blank line,
followed by the SpeX data.
SMASS data are normalized to unity at 0.55 microns. SpeX data are
scaled to fit the SMASS data using the ~0.8 to ~0.9 micron region
where SMASS and SpeX data overlap. SMASS data are held fixed while
the SpeX data are scaled to fit under the criteria of maintaining a
constant first derivative (slope) and minimizing the chi-squared
scattering. Ultimately subjective judgement is used in concluding
the "best fit." Users of these data are advised to apply their own
data normalization algorithm if their model results or science
interpretation is strongly influenced by the final fit between the
independent SMASS visible wavelength spectra and these near-infrared
spectral data sets.
For more information, contact Richard Binzel (rpb at mit.edu)