Recently, satellite-routed sensor systems are expected to be used as early disaster detection systems. The networks efficiently provide data collected from wide areas with small sensor terminals and satellites. In this system, each sensor terminal collects and sends data to monitoring stations on the ground via satellites. Although the future major disaster detection systems require high capacity to manage numerous sensor terminals, it is difficult to collect data from a large number of sensor terminals simultaneously since the bandwidth of each satellite is limited. Hence, an efficient system to allocate the bandwidth to each sensor terminals is required. Moreover, for early disaster detection, the real-time performance is very important. Therefore, in this paper, we discuss an appropriate bandwidth allocation model to construct a next generation satellite-routed sensor system while considering the real-time performance. In the new model, we particularly focus on the relationship between throughput of each sensor terminal and real-time performance, and introduce a method to allocate bandwidth. A numerical analysis is used to validate the new system model.