following where F is the focal length of the optical system, D is the diameter of the optical system and λ is the wavelength. Monopulse feeds The angle to the observed target (e.g. a meteor in meteor studies) can be estimated using amplitude monopulse. In such a configuration, three signals are collected from four feed elements. These signals are the elevation difference signal, the azimuth difference signal and the sum signal. See also Staring array References Radio astronomy Image sensors