Satellite radar interferometry has developed in less than two decades from an exotic new opportunity to an (almost) standard technology. From a geodetic perspective, it combines repeated distance measurements with an imaging capability, while the interferometric basics guarantee very high precision levels, concerning the basic observables. Less well known are the relations with reliability, the precision of the estimated parameters, testing opportunities, significance levels, and network design. In this presentation we will discuss the basic principles of the technology, with special emphasis on its geodetic aspects.