This part of the standard, which is supplementary to Part 1, IEC 835-1-1, describes methods of measu-rement applicable to satellite earth station systems using digital modulation. The object of this part is to provide recommended methods of measurement for assessing the essential properties of satellite earth station systems as well as the associated sub-systems and it is intended to be used in conjunction with Part 1, IEC 835-1-1. Where measurements common to terrestrial radio-relay and satellite earth station systems are required, reference is made to the appropriate section of Part 1, IEC 835-1-1. In such cases, only those special aspects of the measurement appropriate to satellite earth station systems are described in the sections of this Part 3. Where parameters or methods of measurement are applicable only to satellite earth station systems, they are fully described within the appropriate sections of this part.