The near-Earth asteroid population from two decades of observations

Determining the size and orbital distribution of the population of near-Earth asteroids (NEAs) is the focus of intense research, with the most recent models converging to a population of approximately $1000$ NEAs larger than 1 km and up to approximately $10^9$ NEAs with absolute magnitude $H<30$. We present an analysis of the combined observations of nine of the leading asteroid surveys over the past two decades, and show that for an absolute magnitude $H<17.75$, which is often taken as proxy for an average diameter larger than 1 km, the population of NEAs is $920\pm10$, lower than other recent estimates. The population of small NEAs is estimated at $(4 \pm 1)\times 10^8$ for $H<30$, and the number of decameter NEAs is lower than other recent estimates. This population tracks accurately the orbital distribution of recently discovered large NEAs, and produces an estimated Earth impact rate for small NEAs in good agreement with the bolide data.