The Taxonomic Distribution of Mission-Accessible Small Near-Earth Asteroids

Scientific interest in the near-Earth asteroid (NEA) population has grown in recent years, particularly with regards to characterizing the population of mission-accessible NEAs. Mission accessibility is defined by delta-v, the change in velocity required for a spacecraft to rendezvous with a celestial body. With current propulsion technology, spacecraft can reach NEAs whose orbits have delta-V < 7 km/s.Across the entire NEA population, the smallest (d < 1 km) objects have not been well-studied, owing to the difficulty of observing them. These very small objects are often targets of opportunity, observable for only a short period of time after their discovery. Even at their brightest (V ~ 18), these asteroids are faint enough that they must be observed with large ground-based telescopes.The Mission Accessible Near-Earth Object Survey (MANOS) began in August 2013 as a multi-year physical characterization survey that was awarded survey status by NOAO. MANOS will target several hundred mission-accessible NEOs across visible and near-infrared wavelengths, ultimately providing a comprehensive catalog of physical properties (astrometry, light curves, spectra).Thirty-seven small, mission-accessible NEAs were observed between mid 2013 and mid 2014 using the Gemini Multi-Object Spectrograph at Gemini North & South observatories. Taxonomic classifications were obtained by fitting our spectra to the visible wavelength portions of the mean reflectance spectra of the Bus-DeMeo taxonomy (DeMeo et al 2009). The smallest near-Earth asteroids are the likely progenitors of meteorites; we expect the observed fraction of ordinary chondrite meteorites to match that of their parent bodies, S-type asteroids. We present classifications for these objects as well as preliminary results for the distribution of taxa (as a proxy for composition) as a function of object size and compare to the observed fraction of ordinary chondrite meteorites.