Title : Draconitic signals as an orbital-physical phenomenon in GNSS geodesy: Physical origins, modelling, and implications for high-precision earth observation
Abstract:
Draconitic signals represent some of the most prominent periodic components observed in GNSS-derived geodetic time series. These signals are often treated as systematic errors associated with limitations in satellite orbit determination, observation modelling, and geodetic data processing. Nevertheless, their repeated appearance across multiple GNSS constellations suggests that they may originate from fundamental physical processes associated with satellite orbital dynamics rather than from processing artifacts alone. This study examines draconitic signals from an orbital-physical perspective and investigates their underlying physical origins in the context of satellite geodesy and high-precision Earth observation. Particular attention is given to the relationship between the draconitic period, orbital geometry, and non-gravitational forces acting on GNSS satellites. Key factors considered include solar radiation pressure, thermal re-radiation effects, orbital node geometry, and residual modeling errors. Together, these factors can generate periodic signatures perturbations that propagate into geodetic observations and influence the quality of derived geodetic products. A conceptual physical framework is presented that explains the generation and propagation of periodic variations in GNSS coordinate time series and ultimately influence the accuracy of geodetic products. The spectral characteristics of draconitic signals are also examined, together with their implications for high-precision applications such as crustal deformation monitoring, terrestrial reference frame realization, station velocity estimation, and long-term Earth observation. The findings suggest that draconitic signals more appropriately interpreted as deterministic effects of orbital-physical interactions within GNSS systems than as purely stochastic noise or computational artifacts. This interpretation provides a more comprehensive understanding of their origin and behaviour and underscores the importance of integrating orbital physics with advanced geodetic modelling. Such an approach can improve the accuracy and reliability of GNSS-based Earth observation and support the development of more effective mitigation strategies for future geodetic and geophysical investigations.
Keywords: Draconitic Signals; GNSS; Solar Radiation; Non-Gravitational Forces; Time Series Analysis.
