Tholen 1984¶
Observables |
Reflectance Spectra, Visual Albedo |
Wavelength Range |
0.337 - 1.041µm |
Number of Classes |
15 |
Class Assignment |
Absolute |
There are 15 classes. Notation used to flag uncertain (U), indecisive (I), and noisy (:) data is not kept.
The spectral class templates can be loaded using the
classy.taxonomies.tholen.load_templates() function, which returns a
dict containing the classes as keys and the template spectra as values.
The following preprocessing steps are automatically done when using the classy.Spectrum.classify()
method:
Resampling to common wavelength grid
Normalisation to 0.55μm
The preprocessing does not change the wave and refl attributes of the
spectrum.
Tholen used a minimal-tree algorithm to gradually identify clusters and define classes. This means that classes do not have well defined boxes in the principal space and no decision tree is in place.
Following the minimal-tree principle, new observations asteroids are assigned to the class of the closest asteroid from the ECAS dataset in principal component space. An issue may arise for A, Q, V, which occupy a similar small volume.[#f3]_
The resulting class is assigned to the class_tholen attribute. The principal
components scores are accessible via the scores_tholen attribute.
$ classy classify nysa --taxonomy tholen