Coherence theory of radio-astronomical measurements

A unified theory of radio-astronomical measurements is presented within the framework of the theory of partial coherence. It is shown how different coherence functions are related to the spectrum, the brightness distribution, and the polarization of statistical electromagnetic fields, and to their measurement. These coherence functions can be derived from the space-time coherence tensor. Various radio-astronomical techniques for measuring the spectrum, the brightness distribution, and the polarization are discussed with special reference to correlation techniques. The connection between the theory of antennas and that of optical systems is discussed. In both cases the theory of partial coherence provides a unified theoretical foundation and an important framework for future research and development.