The advent of processing satellites which perform demodulation and remodulation of received signals has made it practical to consider satellite communication systems in which the up-link and down-link multiplexing/multiple-access schemes are different. This paper considers a satellite communication system in which channels are demand-assigned, and in which a hybrid time-division/frequencydivision multiple-access approach is employed for the up-link and pure time-division multiplexing is employed for the down-link. This scheme has significant advantage for systems which may be subject to electronic jamming. The user capacity is analyzed in general, and numerical results are given for some specific parameters of interest. Depending on the number of ground terminals in the network, it is found that the user capacity of the system can be limited by either the terminal's or the satellite's channel capacity.