Onboard Equipment in HAPS: The Core of Stratospheric Connectivity
HAPS (High Altitude Pseudo-Satellites) have moved from being an experimental concept to becoming key platforms for aerial and terrestrial connectivity. Operating in the stratosphere, at approximately 20 kilometres altitude, they function as intermediate nodes capable of linking with satellites, relaying towards ground stations and providing direct LTE coverage to users on the surface. The heart of the system resides in its onboard equipment, designed to maintain simultaneous communications across three distinct domains. On one hand, a dual-link satellite module (GEO/LEO) guarantees continuous connection with the global network. Through it, both mission data and differential GNSS return signals are channelled, which are essential for precise positioning and autonomous flight control. In parallel, the HAPS integrates a high-power LTE transceiver that acts as an aerial base station, capable of providing broadband connectivity in areas without terrestrial coverage or affected by emergencies. This module operates in a synchronised manner with the navigation system, making it possible to maintain exact alignment between the HAPS position, antenna coverage and mobile users on the surface. The downlink towards the ground is managed by means of a gateway station with directional antennas and adaptive IP protocols, which balance the load between satellite and terrestrial traffic. This hybrid design ensures low latency and high availability even under adverse atmospheric conditions. Although the technology has matured, challenges persist. Thermal dissipation in communications equipment, electromagnetic interference between modules and energy autonomy remain critical factors. Current developments are focused on flat electronic antennas and multiprotocol routers with dynamic spectrum management, which will enable more stable and scalable operation in future HAPS missions. The integration of all these systems into a single platform represents a decisive step towards a persistent aerial infrastructure, capable of complementing satellites and terrestrial networks within a truly continuous connectivity ecosystem.
NASSAT - Network Satellite Systems