Navigation payload and satellite design for LEO PNT constellation

The Global Navigation Satellite System (GNSS) is a critical component of modern infrastructure, playing a foundational role in sectors such as banking and logistics. However, the current reliance on Mid Earth Orbit (MEO) satellites renders the system to provide weak signals and susceptible to various threats, including jamming and spoofing. This paper asserts that future navigation satellite configurations should be more versatile to enhance service reliability. Leveraging Low Earth Orbit (LEO) satellite constellations offers advantages, such as improved geometry and stronger signals. The proliferation of small, standardized satellites has opened opportunities for cost-effective LEO Positioning, Navigation, and Timing (PNT) constellations. These small satellites could offer single or multi-frequency navigation services. This variation in navigation payload could affect the size and cost of navigation services from LEO PNT constellations. This paper introduces an innovative LEO PNT payload concept tailored for small satellite constellations. It explores the constellation design, optimizing the number and distribution of satellites within the orbits. Through analysis, the constellation design is refined for satellite altitudes based on payload functionalities and coverage requirements. The payload concept extends to a preliminary satellite design, demonstrating the feasibility and cost range of a global system. The paper compares a low-cost payload (single frequency L1 band operation) against a costly payload (dual frequency L1 and L5 band operation) considering short term and long-term clock stability. Other parameters under investigation include GNSS dependence of LEO PNT constellation, size, mass, and overall system cost. Feasibility estimates are provided using commercial-off-the-shelf (COTS) components and systems based on projected power and mass budgets. The study concludes by sharing the relationship between the cost and size of the satellite to potential navigation services use cases. With these considerations, this study establishes the guidance for the development of an efficient and fully operational LEO PNT satellite system based on targeted use case.