Distributions of Radar Angels

A foremost characteristic of large dot radar angels is the wide variation of basic parameter values which they exhibit. This variation is traceable to the nature of the underlying phenomena, i.e., birds and flocks of birds. In this paper, statistical distribution models for the mean radar cross section (RCS) and density of radar angels are obtained, based on a combination of radar and direct ornithological data. The radar cross-section distribution model has been derived from a dimensionless RCS versus wavelength model for individual birds, obtained from measured RCS data which have been scaled to a dimensionless form. This model is applied to ornithological data on populations of birds. The density distribution model is based on statistical reduction of migratory bird data obtained by Lowery´s moon watching experiment, and observed seasonal and diurnal variations of radar angel activity. Both resulting distribution models are closely appproximated by the log-normal distribution. The model parameters for these distributions are given.