Non-Geostationary satellite networks have many advantages to enable ubiquitous wireless environments such as, extensive coverage, disaster-resistance, and efficient power consumption. Furthermore, to use these networks more efficiently, multi-layered satellite networks are a promising approach, due to their ability to achieve increases in network capacity and to detour traffic efficiently, while maintaining the advantages of each layer. However, they suffer from high delay. In this paper, we focus on constellation design of two-layered satellite networks, in particular on the satellite altitude that minimizes the total packet delivery delay of the network. We express the relationship between the total packet delivery delay and the satellite altitude in mathematical form and develop an expression for determining the altitude to minimize total packet delivery delay. Simulation results validate our analyses.