The size distribution of Near-Earth Asteroids from the DECam NEO Survey

We analyzed data from the first year of a survey for Near Earth Objects (NEOs) that we are carrying out with the Dark Energy Camera (DECam) on the 4 meter Blanco telescope at the Cerro Tololo Inter-American Observatory. We implanted synthetic NEOs into the data stream to derive our nightly detection efficiency as a function of magnitude and rate of motion. Using these measured efficiencies and the Solar System absolute magnitudes derived by the Minor Planet Center for the 1377 measurements of 235 unique NEOs detected, we directly derive, for the first time from a single observational data set, the NEO size distribution from 1 km down to 10 meters. We find that there are 10^6.6 NEOs larger than 10 meters. This result implies a factor of ten fewer small NEOs than some previous results (e.g., Harris & D'Abramo 2015, Boslough et al. 2015) but a factor of ten more than Tricarico (2016). This result also implies that the impact risk for small- and medium-sized NEOs is less than previously thought.