LEO-PNT payload architecture and satellite design analysis

Low Earth Orbit (LEO) navigation satellite system versatility has the potential to significantly enhance Positioning, Navigation, and Timing (PNT) service reliability. Leveraging an improved geometry due to closer orbital proximity resulting in higher number of visible satellites and reduced free space loss will ensure stronger and more resilient PNT signals. Given the fact that hundreds of satellites are needed for a LEO constellation with a global coverage, the satellites should remain small to maintain a feasible cost of the mission. This work introduces a small satellite LEO-PNT navigation payload concept tailored for LEO constellations. The navigation payload concept is applied to a preliminary satellite design, demonstrating the feasibility of the system. The paper analyzes the performance of a low-cost payload (single-frequency L1-band operation) against a higher cost payload (dual-frequency L1- and L5-band operation), considering short and medium-term clock stability. Other compared parameters include size, mass, overall system cost, and the dependence of the LEO-PNT constellation on existing Global Navigation Satellite Service (GNSS) infrastructure. Isoflux navigation antenna radiation pattern requirements are also analyzed for different LEO altitudes. In addition, this work provides satellite feasibility estimates (power, mass, and link budgets) based on Commercial Off-The-Shelf (COTS) components and subsystems. This work concludes by presenting a performance analysis of a low and high cost small satellite LEO-PNT payload. The analysis shows that the orbital altitude dependent Carrier-to-Noise density ratio (C/No) of a LEO-PNT navigation signal is equal to or better than the C/No of Medium Earth Orbit (MEO) GNSS signals. Hence, this study provides guidance for the development of an efficient and fully operational LEO-PNT satellite system.