Characteristics of the Ensemble of Close Potentially Hazardous Asteroids

Optimization of search (detection) of near-Earth asteroids (NEAs) is of practical interest. Almost all NEAs larger than ~700 m (90%) are known. However, the modern interpretation of the NEA detection problem includes the requirement for the exhaustive detection of asteroids larger than 10 m. So far, there are no detection systems that meet this requirement, either in the world or in Russia, but work is underway to create them. This paper considers some astronomical justifications for choosing an effective strategy for searching for NEAs, especially for asteroids that can enter near-Earth space, i.e. approach the Earth at a distance of less than 1.5 million km. In this work, asteroids that will enter the near-Earth space within the next 100 years are classified as close potentially hazardous asteroids (CPHA). Practically significant distributions of asteroids are constructed — by celestial sphere, by brightness and by angular velocity. Comparison of distributions for the ensemble of all NEAs larger than 10 m (according to the NEOMOD model) and for the ensemble of CPHAs showed that the distributions of CPHAs over the celestial sphere and by angular velocity differ from such distributions for all NEAs. In particular, the mean angular velocities of CPHA in a large range of distances (0.1–0.5 au) are much (an order of magnitude) lower than for all NEAs located at the same distances. It is important to take into account the features of the CPHA distributions when developing a strategy for their detection program.