PhD Defence Sarah Schultz Beeck

Principal supervisor

• Associate Professor Daniel H. Olesen, DTU Space

Co-supervisors

• Anna B.O. Jensen, AJ Geomatics, Denmark
• Lars Stenseng, Bedrock Solutions, Denmark

Examiners:

• Senior Advisor Sine Munk Hvidegaard, DTU Space
• Principal Researcher Scientist and Assistant Director Anthea Coster, MIT Haystack, USA
• Adjunct Professor Jan Johansson, Chalmers, Sweden

Chairperson at defence

• Senior Researcher Jens Olaf Pepke Pedersen, DTU Space

Summary

Over the past decades, society has become increasingly reliant on satellite-based positioning. This reliability has introduced a vulnerability to the solar-induced changes in the upper layer of the atmosphere, the ionosphere, that interferes with traversing satellite signals on their way to the receiver on the ground. These solar impacts on technology are termed space weather and are of particular interest in the Arctic region, where processes in the ionosphere are complex and dynamic. Reliable navigation is critical for various activities in the Arctic, including maritime transport, resource exploration, and scientific research. Understanding the impact of space weather on satellite-based navigation signals is essential for ensuring the safety and reliability of navigation systems in this challenging environment. This PhD thesis investigates the process towards a real-time space weather alert system for users of satellite-based positioning in Greenland.

The analyses of the PhD are based on data from two Global Navigation Satellite System (GNSS)networks in Greenland, the Greenland GPS Network (GNET) and the Space Weather Forecasting for Arctic Defence Operations (SWADO) network. Data from GNET was used to investigate two interpolation methods for mapping variation in the ionospheric electron content over Greenland. The suitable choice of method was found to depend on the level of geomagnetic activity. Further, it was suggested that a network specifically designed to monitor the ionosphere and output real-time indices be implemented. In 2021, the SWADO network was installed along the coast of Greenland to monitor the ionosphere and form the basis of a future real-time alert system. One year of SWADO and GNET data was utilised to investigate the relation between an index, quantifying high-frequency disturbance on the GNSS signal phase, and impacts on GNSS measured by slips in signal tracking and data outages. It demonstrated that the European GNSS constellation Galileo experienced more slips in signal tracking relative to the American constellation GPS, which experienced a larger number of data outages. Apart from being signal-specific, the impact on satellite navigation also depends on the receiver and user.

When issuing space weather alerts based on GNSS data, it is essential to know whether disturbances affecting the use of GNSS are space weather-related. A signal in geomagnetic ground observationswas examined as a potential support to identify space weather-related fluctuation in GNSS signals inreal-time. The performance of the magnetic signal was found to vary with latitude and magnetic localtime, demonstrating the highest potential in the nightside auroral region.

In conclusion, space weather alerts are an essential tool in addressing the challenges posed to satellite based navigation in the Arctic, ensuring the continued functionality and reliability of GNSS systems in this unique and dynamic environment.