A large number of technologies are used in a satellite because it is hard difficult to repair and replace its components after it has been launched. Furthermore, there are many threats to the satellite such as software aging, environmental problems and network attacks. Because of this nature, it is important that the satellite operates well in spite of the occurrence of hardware and/or software faults. In particular, software aging in the on-board computer (OBC) causes unavailability of a whole satellite system. In this paper, we propose to adopt software rejuvenation for OBC in conjunction with cold, hot and warm standby redundancy in a satellite system. We use stochastic reward nets (SRN) to model OBC with cold, hot and warm standby redundancy and model OBC with that redundancy with software rejuvenation. We compare the models in terms of steady state availability and downtime cost. Sensitivity analysis with respect to some parameters is used to find bottlenecks of the models. Finally, we present a reliability model and analysis with cost consideration.