Typical first responder scenarios will often see compromised, destroyed or non-existing terrestrial network capabilities. Still some ad-hoc terrestrial cellular technology can help to improve the EUTSATfinder offering of a quickly deployable, resilient, robust infrastructure, by means of meaningful integration of respective portable or mobile terrestrial network components. As a strong candidate for that we will further present an in-situ 5G campus network, but this can conceptionally be seen also as a good representative for similar solutions based on 4G or future 6G technology. Moreover, the 3GPP evolution with the emerging non-terrestrial network (NTN) architectures integrating 6G networks with satellite and aerial communications in a systematic and strategic way, is a strong motivation to put some focus exactly on that 5G campus network integration and inter-operability with both, (i) on-site drones and satellite terminals to provide extended in-situ access network capabilities, and (ii) the primary governmental and secure long-distance backhaul/backbone satcom Athena Fidus, via the shielding SATCOM HUB.

Clearly, the most important R&I challenge to be addressed in this context is the seamless inter-operability and handover between satellite and terrestrial communications networks providing overall secure governmental communications services. Initial simple but resilient interoperability and handover procedures are established and tested in the existing solutions used by partner ATM: these include full diversity of 5G and satcom links wherever available, mainly for C2 traffic, and fallback operation of satcom links for payload traffic when a cellular network is (temporarily) not available. Further more advanced handover protocols considering service prioritization (C2 over payload etc.) and optimized cost and performance routing in multilink scenarios are on the development roadmap and will be implemented and integrated in the EUSATfinder solution.