Characteristics of the Ensemble of Close Potentially Hazardous Asteroids

To optimize the search for (detection of) near-Earth asteroids (NEAs) is of practical interest. Almost all NEAs larger than ~700 m are known (more than 90%). However, the modern interpretation of the problem of detecting NEAs includes the requirement to detect a great number of asteroids larger than 10 m in size. So far, there are no detecting systems that meet this requirement, either in the world or in Russia, but work is underway to create them. This paper considers some of astronomical grounds for choosing an effective strategy in searching for NEAs, especially for asteroids that can enter the near-Earth space (NES), i.e., approach the Earth at a distance of less than 1.5 million km. In our paper, asteroids that are expected to enter the NES within the next 100 years are classified as close potentially hazardous asteroids (CPHAs). We constructed practically important distributions of asteroids across the celestial sphere, brightness, and angular velocity. As the comparison of the distributions built for the ensemble of all NEAs larger than 10 m (according to the NEOMOD simulator) and for the ensemble of CPHAs showed, the distributions of CPHAs over the celestial sphere and the angular velocity differ from the corresponding distributions of all NEAs. Particularly, in a wide interval of distances, from 0.1 to 0.5 AU, the mean angular velocities of CPHAs are on average an order of magnitude lower than those of all NEAs located at the same distances. When developing a strategy for detecting CPHAs, it is important to take into account the characteristics of their distributions.