The paper gives details of the performance and accuracy of the communications system monitor (CSM) which is used in conjunction with the Australian National Satellite System (AUSSAT). The equivalent isotropic radiated power (EIRP), frequency and carrier/noise ratio of all carriers are routinely monitored by the CSM as well as a range of baseband parameters for FM/TV and FDM/FM signals. The CSM capability to measure a number of satellite parameters and obtain remote antenna patterns is described. Details are provided of the accuracy of the CSM as determined during extensive factory testing. The results show that the CSM is a very accurate system for the monitoring of both satellite traffic and satellite transponder parameters. Procedures used for setting up carriers for the testing of the CSM are also included. The results presented are those obtained during extensive factory testing of the system. Following installation of the CSM additional carrier types and measurements have been incorporated in the system.