neoproperties aggregates values for taxonomy assignments from the literature. The literature resources currently included in the neoproperties database are listed on the Data Sources page. neoproperties groups the literature taxonomies into complexes and the complexes are grouped into prime complexes.

neoproperties.nasa.gov reports taxonomies in the Bus-DeMeo system (DeMeo et al. 2009). The bulk of recent taxonomy determinations are provided in the Bus-DeMeo system (e.g., Thomas et al. 2014, DeMeo & Carry 2013; DeMeo et al. 2014; Carry et al. 2016). We have included some taxonomies that originally were determined in the Bus system (Bus & Binzel 2002b; Binzel et al. 2004 ). When a reference reported the taxonomy in the Bus system, we translated to the Bus-Demo system using the following rules.

neoproperties.nasa.gov utilizes several symbols to modify the primary taxonomy.

Multiple Taxonomy Assignments

When multiple taxonomy assignments are available in the literature, neoproperties displays all the unique taxonomy assignments separated by a semicolon. Since the data used to determine the taxonomy is usually taken during a relatively brief part of the asteroid's rotation curve, multiple taxonomy assignments might be representative of asteroid surface variations. Preserving the variety of taxonomy assignments can allow the user insight to the possible complexity of the asteroid's surface.

The Bus-DeMeo taxonomies can be grouped into complexes. A complex is identified by an ampersand (&) followed by the letter of the complex in neoproperties.nasa.gov. For example, &C (complex C) is differentiated from C (taxonomy C) by the fact that &C includes a number of taxonomy classes. The table below identifies which taxonomies are grouped into which complexes. The mapping from taxonomy to complex is based on Tables 2 and 3 of DeMeo et al 2009, but includes refinements from Table 2 and §5.2 in DeMeo & Carry 2013. We follow the logic and intent of DeMeo & Carry 2013 when defining complex as a broader combination of certain taxonomies (or "classes"), "The C-complex encompasses the region including C-, Cb-, Cg-, Cgh-, and Ch-types. The S-complex encompasses the S-, Sa-, Sq-, Sr-, and Sv-types. The X-complex includes X-, Xc-, Xe-, Xk-, and T-types. The classes that are maintained individually are A, B, D, L, K, Q, and V." We note that DeMeo & Carry 2013 strive to keep taxonomy definitions, and complex definitions, as consistent as possible with previous taxonomy systems and preserve the uniqueness of "more exotic (taxonomic) classes, restricting A- and D-types to the outliers with the reddest slopes, and Q- and V-types with the deepest bands." DeMeo & Carry 2013 also segregate B and L but combine the rare O taxonomy into the &S complex and the rare R, which may overlap the V taxonomy, also into the &S complex. The &X/C complex encompasses C/X and X/C taxonomic classes such as occur for NEOs (e.g., Thomas et al. 2014) as well as for inner main belt asteroids (DeMeo et al. 2014c); the &X/C complex samples the proximity of principal components for &X and &C (described by taxonomies with relatively featureless spectra and red slopes, DeMeo et al. 2015; Asteroids IV 2015, p13-41).

If competing complex assignments are &C versus &S or &S versus &X, then both taxonomy assignments are kept ('tracked') and denoted by a semi-colon like &C; &S and &S; &X.

Note that this is different logic than in DeMeo & Carry 2013 where if two competing taxonomy assignments differ as X versus C, C versus S, or S versus X then (U)known is assigned; our choice reflects our desire to include information on complex, even when the assignment of complex cannot discriminate by majority between &X and &C.

neoproperties.nasa.gov reports ComplexPrime. ComplexPrime is a classification of broad compositional groups based on taxonomic complex, into $C, $X, and $S-complex primes. Broad groupings into these prime complexes are discussed by many authors (e.g., Carry et al. 2016, DeMeo & Carry 2013, Nesvorný et al. 2005).

The Bus system relies on spectral data from ~0.4–0.8 µm and the Bus-DeMeo system relies on spectral data from ~0.4–2.4 µm or visual photometry and ~0.8–2.4 µm spectra, which includes important diagnostic bands in the near-IR. Notably, the broader spectral coverage provides greater constraints on the surface composition but the characterization provided at shorter wavelengths through the Bus system is traceable to the broader wavelength range of the Bus-DeMeo system (DeMeo et al. 2009). Taxonomy assignments in the Tholen photometric system and the translation from the Tholen system to Bus-DeMeo system are planned for future builds of this data base. The availability of on-line taxonomy assignment tools for spectra holds the intent to improve the consistency of assignments in the Bus-DeMeo system (see asteroid spectrum classification using Bus-DeMeo taxonomy). Taxonomic classification using SDSS photometry is possible when vetted by photometric templates of 371 spectra used to create the Bus-DeMeo taxonomy. The strategy is to use the taxonomy definitions for the principal components as established by analyses of spectra to provide taxonomic class assignments for photometry (Fig. 4 of DeMeo & Carry 2013), allowing taxonomic assignments to be made for 34,503 asteroids and enabling studies of the composition-mass distribution of the asteroid inner-, middle-, and outer-belts (DeMeo & Carry 2014b; DeMeo & Carry 2013).