This Standard defines the radio communication techniques used for the transfer of information between spacecraft and Earth stations in both directions, and for the tracking systems used for orbit determination. It includes the following: • frequency allocation, assignment and use; requirements on transmitted signals concerning, for example, spectral occupation, RF power levels, protection of other radio services; • definition of the permissible modulation methods and parameters; • specification of the major technical requirements relevant for the interface between spacecraft and Earth stations; • operational aspects, such as acquisition;• cross-support.This Standard is applicable to all spacecraft supported by Earth stations1 and to all controlled Earth stations operating in the Space Operation, Space Research and Earth Exploration-Satellite services as defined in the ITU Radio Regulations.2