  Recent developments in the aerospace industry have led to a dramatic
reduction in the manufacturing and launch costs of low Earth orbit satellites.
The new trend enables the paradigm shift of satellite-terrestrial integrated
networks with global coverage. In particular, the integration of 5G
communication systems and satellites has the potential to restructure
next-generation mobile networks. By leveraging the network function
virtualization and network slicing, the orbital 5G core networks will
facilitate the coordination and management of network functions in
satellite-terrestrial integrated networks. We are the first to deploy a
lightweight 5G core network on a real-world satellite to investigate its
feasibility. We conducted experiments to validate the onboard 5G core network
functions. The validated procedures include registration and session setup
procedures. The results show that the 5G core network can function normally and
generate correct signaling.
