Hybrid GNSS/LEO PNT with Safran’s Skydel-Powered GNSS Simulator: From Constellation Design to Receiver-Level Performance

Ryan Ranaivoharison*, Theo Carbillet, Mohamed Tamazin, Pierre-Marie Le Véel

Low Earth Orbit (LEO) satellite constellations are emerging as valuable complements to traditional Global Navigation Satellite Systems (GNSS) for Positioning, Navigation, and Timing (PNT). These multi-orbit systems offer enhanced resilience, faster Time to First Fix (TTFF), and improved robustness in degraded or contested environments. Hybrid GNSS + LEO architectures are particularly effective in urban canyons, indoor locations, and interference-prone settings where conventional GNSS performance is limited or unreliable. This paper presents a flexible and comprehensive simulation and testing framework built on Safran’s high-performance GNSS simulation engine, powered by Skydel, a software-defined platform recognized for its real-time, high-fidelity signal generation and industry-leading flexibility. The framework enables detailed modeling of both GNSS and LEO constellations, including dynamic orbital mechanics, time-varying visibility, and precise environmental control to support complex test scenarios. With Skydel’s deterministic execution, engineers and researchers can replicate and stress-test PNT systems under a broad range of configurable impairments, including jamming, spoofing, urban masking, multipath, and signal dropouts. We evaluate key system-level design factors and their influence on critical PNT performance indicators, such as TTFF, signal availability, Doppler dynamics, and positioning accuracy. A StarNav GNSS receiver is integrated into the testbed and evaluated across three operational modes: GNSS-only, LEO-only, and hybrid GNSS/LEO. This multi-modal assessment supports performance benchmarking and trade-off analysis in realistic and mission-relevant conditions. Results highlight how the Skydel-powered simulation environment provides a scalable, cost-effective, and repeatable platform for validating next-generation hybrid PNT architectures. Its software-defined design, real-time performance, and support for rapid scenario development make it a critical enabler for commercial innovation and mission-critical defense applications where trust, performance, and adaptability are essential.

Keywords: GNSS, LEO constellations, hybrid PNT, skydel, interference.