This paper deals with the initial integrity evaluation of the navigation information provided by the multilayer GNSS and LEO-PNT constellation. Although, the global satellite navigation systems (GNSS) play indispensable role in almost all aspects of today’s society, their signals are prone to intentional or accidental interference. Therefore, low Earth orbit (LEO) constellations aiming at position, navigation, and timing (PNT) solution have recently been introduced as their extension. The LEO-PNT constellations are planned to contain hundreds of SVs with better interference resilience and geometric diversity. As a consequence, the multi-layer GNSS and LEO-PNT constellation was shown to offer more accurate PNT solution. In this paper, we focus on another important aspect of the multi-layer navigation information, which is its integrity assessment. In particular, we analyse possible dependencies between GNSS and LEO-PNT constellations and their impact on the integrity evaluated using the solution separation. The analysis is supported by the numerical simulations using GPS and LEO-PNT constellations with 32 and 441 satellites, respectively.

This paper deals with the resilient time provision based on an ensemble of clocks. In particular, the emphasis is laid on the combination of clock outputs and detecting possible faults. Two classes of fault detection methods, namely model-based and AI/ML-based, are discussed and analysed. In addition, a novel fault detection technique based on the solution separation principle is proposed and tailored for the area of the time provision. Selected fault detection methods are numerically evaluated using a model of an atomic clock ensemble.