NEOMOD: A New Orbital Distribution Model for Near-Earth Objects

Near-Earth Objects (NEOs) are a transient population of small bodies with orbits near or in the terrestrial planet region. They represent a mid-stage in the dynamical cycle of asteroids and comets, which starts with their removal from the respective source regions-the main belt and trans-Neptunian scattered disk-and ends as bodies impact planets, disintegrate near the Sun, or are ejected from the solar system. Here we develop a new orbital model of NEOs by numerically integrating asteroid orbits from main-belt sources and calibrating the results on observations of the Catalina Sky Survey. The results imply a size-dependent sampling of the main belt with the.6 and 3:1 resonances producing similar or equal to 30% of NEOs with absolute magnitudes H = 15 and similar or equal to 80% of NEOs with H = 25. Hence, the large and small NEOs have different orbital distributions. The inferred flux of H < 18 bodies into the 3:1 resonance can be sustained only if the main-belt asteroids near the resonance drift toward the resonance at the maximal Yarkovsky rate (similar or equal to 2 x 10(-4) au Myr(-1) for diameter D = 1 km and semimajor axis a = 2.5 au). This implies obliquities theta similar or equal to 0 degrees for a < 2.5 au and theta similar or equal to 180 degrees for a > 2.5 au, both in the immediate neighborhood of the resonance (the same applies to other resonances as well). We confirm the size-dependent disruption of asteroids near the Sun found in previous studies. An interested researcher can use the publicly available NEOMOD Simulator to generate user-defined samples of NEOs from our model.