Space weather impacts on Geodesy

Space Weather refers to events on the Sun that have an impact on terrestrial technologies and man-made satellites. The Global Navigation Satellite System (GNSS) is extensively used for Geodesy and is subject to Space Weather impacts in several ways. These impacts all have the potential to reduce the accuracy of geodetic measurements utilizing GNSS.  The importance of Space Weather to the Geodesy community has been recognized by the establishment of the Focus Area on Geodetic Space Weather Research (FA-GSWR) (https://ggos.org/about/org/fa/geodetic-space-weather-research/)

The objectives of the FA-GSWR include the development of methodologies to deal with:

• The ionosphere, since the measurements of most of the space-geodetic observation techniques are depending on the properties of the ionosphere along the ray path of an electromagnetic wave between transmitters on satellites and receivers on the ground,
• The thermosphere, since the thermospheric drag is the most important deceleration effect on Low-Earth Orbiting (LEO) satellites that affects the lifetime of such satellites, which are often used for Earth observation.
• The history, experience and state of the art in developing and using sophisticated analysis techniques and modelling approaches for the estimation of the impacts of space weather on geodetic measurements.

This presentation will provide an overview of the nature and frequency of Space Weather events and how they impact technologies related to Geodesy. This will include the occurrence of ionospheric scintillation affecting signals from GNSS satellites to receivers on the ground, and the resulting loss-of-lock on GNSS satellites that compromises the accuracy of position estimates. Typical values of fluctuations in the position estimates derived from both single frequency geodetic GNSS receivers and dual frequency geodetic reference receivers during space weather events will be presented.

The space weather services provided by the South African National Space Agency (SANSA) and other Regional Space Weather Warning Centres associated with the International Space Environment Service (ISES) will be presented as well as the state of the art in the prediction of ionospheric total electron content and ionospheric scintillation.