EVALUATION OF AN NEO CLOSE APPROACH FREQUENCY INDEX FOR PUBLIC/MEDIA RELEASE PURPOSES

There is currently no metric to discern the relative importance of an asteroid close approach with the Earth from the rest. This typically leads to communication media releasing information on close approach events under undefined criteria. This further means that, on many occasions, they inform about events that lack relevance or are publicised to levels which are not justified in terms of objective considerations. The evaluation of that relevance is further complicated by the fact that there are many factors that play a role in this subject, as asteroid size, minimum close approach distance, close approach velocity, actual NEO population, etc. In this paper, we establish an objective criterion to evaluate the expected frequency for the close approach of an NEO, based on the current estimates of the population of such objects, the object absolute magnitude and the parameters of the close approach. In addition, we propose a scalar close approach index that can be used to discriminate the relevance of an NEO close approach with the Earth, and we apply it to the current list of close approaches reported in ESA’s NEO Coordination Centre web portal.