On the angular resolution of multiple targets

The angular accuracy obtainable from an aperture of fixed size is considered, with emphasis on the multiple target case. By means of the Cramer- Rao Inequality, a lower bound to the measurement variance is computed. In addition, the degradation due to uncertainties in the number of targets present is considered. Loss of accuracy is small until the targets approach to within one beamwidth, at which point the degradation becomes severe.