My research develops Guidance, Navigation and Control (GNC) solutions for close formation flying in Earth Observation. Distributed satellite architectures promise higher measurement accuracy and improved spatial resolution compared with monolithic spacecraft. Yet maintaining separations of only a few metres, often below 10 metres, is challenging for control and, especially, for relative navigation. Next‑generation missions demand sub‑millimetre relative positioning, making navigation performance a critical requirement.

The work builds on studies at Politecnico di Milano, particularly the TriHex concept: three satellites flying in a tightly controlled General Circular Orbit formation with an approximate five‑metre relative radius to enable interferometric radiometry. Scientific objectives depend on preserving the relative geometry to ensure measurement accuracy and operational safety in a constrained environment. This highlights the need for reliable, autonomous relative navigation.

A further focus is the effect of formation size. Past formation‑flying missions typically used two satellites, with simpler geometries and interaction patterns. TriHex introduces a three‑satellite architecture, increasing the complexity of inter‑satellite visibility, information sharing and navigation geometry. The research studies how satellites should interact to maintain robust, accurate relative state estimates under tight constraints. The resulting methods are designed to scale beyond three spacecraft, supporting future swarm missions.

The core of the work is the design of robust relative navigation algorithms based solely on Global Navigation Satellite Systems (GNSS). Formation‑flying missions have historically relied on GNSS, primarily GPS. Current concepts increasingly adopt multi‑constellation strategies, particularly combining GPS and Galileo, to improve measurement availability and diversity and to exploit complementary signal characteristics.

Although the emphasis is on algorithms, performance depends on the observables. The research uses appropriately modelled pseudorange and carrier‑phase measurements, accounting for the principal error sources and delays that drive achievable accuracy. This provides the foundation for high‑precision, resilient relative navigation.

Ultimately, the aim is to enable the next generation of distributed Earth Observation missions by delivering autonomous, high‑accuracy, GNSS‑based relative navigation solutions that are safe in close proximity and scalable from triads such as TriHex to larger formations and swarms.

Click here to view my poster.