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A Spectrophotometric Taxonomic Survey of Small near-Earth Asteroids using UKIRT

Presentation #113.03 in the session Asteroids: Observational Surveys (Oral Presentation)

Published onOct 23, 2023
A Spectrophotometric Taxonomic Survey of Small near-Earth Asteroids using UKIRT

We present an overview of the taxonomic classification of small asteroids using the 3.8 m United Kingdom Infrared Telescope (UKIRT). Our project consists of a near-infrared (NIR) rapid-response spectrophotometry survey focused on characterizing small recently-discovered near-Earth asteroids (NEAs) using UKIRT’s Wide-Field Camera (WFCAM). We have collected NIR photometry covering the wavelength range from 0.8 to 2.3 µm by implementing Z, J, H, and K band observations to determine the taxonomic classification of small NEAs. These filters cover characteristic fingerprints of the asteroid’s absolute reflectance (i.e., olivine and pyroxene absorption features, reflectance slopes, and relative albedo). Furthermore, these broadband filters provide much greater sensitivity than spectroscopy, thus making possible the characterization of small asteroids (<150 m) by determining their taxonomic classification. Thus, asteroid colors are directly correlated with the surface’s composition and, by extension, its taxonomy. We have employed ground-truth spectra of asteroids for which Bus-DeMeo taxonomy is known and retrieved their corresponding colors by using a spectral convolution approach with the response function of each of the Z, J, H, and K filters. We used these colors to create a training sample that is used to provide probabilistic taxonomic classification using machine-learning tools.

Our survey currently contains more than 350 small recently-discovered NEAs for which we will provide probabilistic taxonomic classification. Around 80% of our survey is populated by objects smaller than 170 m in diameter. In this size regime, our survey is about 2.8 times larger than the largest NEA spectroscopic survey (MITHNEOS). With such a dataset on small NEAs, we aim to understand the fractional taxonomic distribution of small asteroids better and determine discrepancies with both meteor falls statistics and larger bodies in the NEA population.

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