Presentation #514.04 in the session Observing Physical Properties of NEOs Part II.
Since 2018, we observed 52 near-Earth objects (NEO) with absolute magnitudes > 22.0 and V magnitudes > 19.0 with the 1.8-m Vatican Advanced Technology Telescope (VATT). The project continues to focus on the physical characterization of small NEOs (Kikwaya et al. 2015, 2018, 2019, 2021), mainly to determine taxonomic type.
Spectroscopy could not be used as the V magnitude of the NEOs is faint and the limiting magnitude of spectrometers on the VATT telescope only reach a V magnitude of 16. The best method for taxonomic classification of faint NEOs remains spectrophotometry with broadband BVRI filters [e.g., B, V: Chapman et al. (1975); Johnson-Cousins B, V, R: Bowell et al. (1978); ECAS: Tholen (1984)].
We computed the color indices B-V, V-R, and V-I to quickly classify them among the 4 primary asteroid types: C, S, X, and D [Zellner et al. (1985); Yoshida et al. (2004); Dandy et al. (2007); Kikwaya et al. (2018, 2019)]. To identify subtypes (C, Cg, Cgh, S, Sq, …), we computed their relative reflectance and compared them with published spectroscopy [Bus and Binzel (2002a); Bus and Binzel (2002b); Binzel et al. (2019)]. The comparison is done using either a standard deviation or chi-squared test [Popescu, Birlan, and Nedelcu (2012), Kikwaya et al. 2021]. We also checked for matches between asteroid reflectance and laboratory meteorite spectra covering visible and near-infrared wavelengths from the Brown RELAB data (Kikwaya et al. 2021). But concentrating only on the visible part of the spectrum, we realized that some asteroids were a match for both carbonaceous and ordinary chondrite meteorites. In these ambiguous cases, we determined the escape mechanism of each NEO and assumed that LL chondrites originate from the inner Main Belt nu6 resonance, H chondrites from the 3:1 resonance, and L chondrites from the outer Main Belt [Binzel et al. (2019), Kikwaya et al. 2021)].